jdk8-mips64-public/hotspot: src/os/linux/vm/os_linux.cpp@c7004d700b49 (annotated)

src/os/linux/vm/os_linux.cpp@c7004d700b49 (annotated)

src/os/linux/vm/os_linux.cpp

Wed, 25 Aug 2010 21:29:05 -0400

author: dholmes
date: Wed, 25 Aug 2010 21:29:05 -0400
changeset 2105: c7004d700b49
parent 2036: 126ea7725993
child 2220: 1c352af0135d
permissions: -rw-r--r--

6978641: Fix for 6929067 introduces additional overhead in thread creation/termination paths
Summary: Disable stack bounds checks in product mode other than for the initial thread
Reviewed-by: coleenp, jcoomes, aph

 /*
  * Copyright (c) 1999, 2009, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 only, as
  * published by the Free Software Foundation.
  *
  * This code is distributed in the hope that it will be useful, but WITHOUT
  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  * version 2 for more details (a copy is included in the LICENSE file that
  * accompanied this code).
  *
  * You should have received a copy of the GNU General Public License version
  * 2 along with this work; if not, write to the Free Software Foundation,
  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  *
  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  * or visit www.oracle.com if you need additional information or have any
  * questions.
  *
  */
 # define __STDC_FORMAT_MACROS
 // do not include  precompiled  header file
 # include "incls/_os_linux.cpp.incl"
 // put OS-includes here
 # include <sys/types.h>
 # include <sys/mman.h>
 # include <sys/stat.h>
 # include <sys/select.h>
 # include <pthread.h>
 # include <signal.h>
 # include <errno.h>
 # include <dlfcn.h>
 # include <stdio.h>
 # include <unistd.h>
 # include <sys/resource.h>
 # include <pthread.h>
 # include <sys/stat.h>
 # include <sys/time.h>
 # include <sys/times.h>
 # include <sys/utsname.h>
 # include <sys/socket.h>
 # include <sys/wait.h>
 # include <pwd.h>
 # include <poll.h>
 # include <semaphore.h>
 # include <fcntl.h>
 # include <string.h>
 # include <syscall.h>
 # include <sys/sysinfo.h>
 # include <gnu/libc-version.h>
 # include <sys/ipc.h>
 # include <sys/shm.h>
 # include <link.h>
 # include <stdint.h>
 # include <inttypes.h>
 #define MAX_PATH    (2 * K)
 // for timer info max values which include all bits
 #define ALL_64_BITS CONST64(0xFFFFFFFFFFFFFFFF)
 #define SEC_IN_NANOSECS  1000000000LL
 ////////////////////////////////////////////////////////////////////////////////
 // global variables
 julong os::Linux::_physical_memory = 0;
 address   os::Linux::_initial_thread_stack_bottom = NULL;
 uintptr_t os::Linux::_initial_thread_stack_size   = 0;
 int (*os::Linux::_clock_gettime)(clockid_t, struct timespec *) = NULL;
 int (*os::Linux::_pthread_getcpuclockid)(pthread_t, clockid_t *) = NULL;
 Mutex* os::Linux::_createThread_lock = NULL;
 pthread_t os::Linux::_main_thread;
 int os::Linux::_page_size = -1;
 bool os::Linux::_is_floating_stack = false;
 bool os::Linux::_is_NPTL = false;
 bool os::Linux::_supports_fast_thread_cpu_time = false;
 const char * os::Linux::_glibc_version = NULL;
 const char * os::Linux::_libpthread_version = NULL;
 static jlong initial_time_count=0;
 static int clock_tics_per_sec = 100;
 // For diagnostics to print a message once. see run_periodic_checks
 static sigset_t check_signal_done;
 static bool check_signals = true;;
 static pid_t _initial_pid = 0;
 /* Signal number used to suspend/resume a thread */
 /* do not use any signal number less than SIGSEGV, see 4355769 */
 static int SR_signum = SIGUSR2;
 sigset_t SR_sigset;
 /* Used to protect dlsym() calls */
 static pthread_mutex_t dl_mutex;
 ////////////////////////////////////////////////////////////////////////////////
 // utility functions
 static int SR_initialize();
 static int SR_finalize();
 julong os::available_memory() {
   return Linux::available_memory();
 }
 julong os::Linux::available_memory() {
   // values in struct sysinfo are "unsigned long"
   struct sysinfo si;
   sysinfo(&si);
   return (julong)si.freeram * si.mem_unit;
 }
 julong os::physical_memory() {
   return Linux::physical_memory();
 }
 julong os::allocatable_physical_memory(julong size) {
 #ifdef _LP64
   return size;
 #else
   julong result = MIN2(size, (julong)3800*M);
    if (!is_allocatable(result)) {
      // See comments under solaris for alignment considerations
      julong reasonable_size = (julong)2*G - 2 * os::vm_page_size();
      result =  MIN2(size, reasonable_size);
    }
    return result;
 #endif // _LP64
 }
 ////////////////////////////////////////////////////////////////////////////////
 // environment support
 bool os::getenv(const char* name, char* buf, int len) {
   const char* val = ::getenv(name);
   if (val != NULL && strlen(val) < (size_t)len) {
     strcpy(buf, val);
     return true;
   }
   if (len > 0) buf[0] = 0;  // return a null string
   return false;
 }
 // Return true if user is running as root.
 bool os::have_special_privileges() {
   static bool init = false;
   static bool privileges = false;
   if (!init) {
     privileges = (getuid() != geteuid()) || (getgid() != getegid());
     init = true;
   }
   return privileges;
 }
 #ifndef SYS_gettid
 // i386: 224, ia64: 1105, amd64: 186, sparc 143
 #ifdef __ia64__
 #define SYS_gettid 1105
 #elif __i386__
 #define SYS_gettid 224
 #elif __amd64__
 #define SYS_gettid 186
 #elif __sparc__
 #define SYS_gettid 143
 #else
 #error define gettid for the arch
 #endif
 #endif
 // Cpu architecture string
 #if   defined(ZERO)
 static char cpu_arch[] = ZERO_LIBARCH;
 #elif defined(IA64)
 static char cpu_arch[] = "ia64";
 #elif defined(IA32)
 static char cpu_arch[] = "i386";
 #elif defined(AMD64)
 static char cpu_arch[] = "amd64";
 #elif defined(ARM)
 static char cpu_arch[] = "arm";
 #elif defined(PPC)
 static char cpu_arch[] = "ppc";
 #elif defined(SPARC)
 #  ifdef _LP64
 static char cpu_arch[] = "sparcv9";
 #  else
 static char cpu_arch[] = "sparc";
 #  endif
 #else
 #error Add appropriate cpu_arch setting
 #endif
 // pid_t gettid()
 //
 // Returns the kernel thread id of the currently running thread. Kernel
 // thread id is used to access /proc.
 //
 // (Note that getpid() on LinuxThreads returns kernel thread id too; but
 // on NPTL, it returns the same pid for all threads, as required by POSIX.)
 //
 pid_t os::Linux::gettid() {
   int rslt = syscall(SYS_gettid);
   if (rslt == -1) {
      // old kernel, no NPTL support
      return getpid();
   } else {
      return (pid_t)rslt;
   }
 }
 // Most versions of linux have a bug where the number of processors are
 // determined by looking at the /proc file system.  In a chroot environment,
 // the system call returns 1.  This causes the VM to act as if it is
 // a single processor and elide locking (see is_MP() call).
 static bool unsafe_chroot_detected = false;
 static const char *unstable_chroot_error = "/proc file system not found.\n"
                      "Java may be unstable running multithreaded in a chroot "
                      "environment on Linux when /proc filesystem is not mounted.";
 void os::Linux::initialize_system_info() {
   set_processor_count(sysconf(_SC_NPROCESSORS_CONF));
   if (processor_count() == 1) {
     pid_t pid = os::Linux::gettid();
     char fname[32];
     jio_snprintf(fname, sizeof(fname), "/proc/%d", pid);
     FILE *fp = fopen(fname, "r");
     if (fp == NULL) {
       unsafe_chroot_detected = true;
     } else {
       fclose(fp);
     }
   }
   _physical_memory = (julong)sysconf(_SC_PHYS_PAGES) * (julong)sysconf(_SC_PAGESIZE);
   assert(processor_count() > 0, "linux error");
 }
 void os::init_system_properties_values() {
 //  char arch[12];
 //  sysinfo(SI_ARCHITECTURE, arch, sizeof(arch));
   // The next steps are taken in the product version:
   //
   // Obtain the JAVA_HOME value from the location of libjvm[_g].so.
   // This library should be located at:
   // <JAVA_HOME>/jre/lib/<arch>/{client|server}/libjvm[_g].so.
   //
   // If "/jre/lib/" appears at the right place in the path, then we
   // assume libjvm[_g].so is installed in a JDK and we use this path.
   //
   // Otherwise exit with message: "Could not create the Java virtual machine."
   //
   // The following extra steps are taken in the debugging version:
   //
   // If "/jre/lib/" does NOT appear at the right place in the path
   // instead of exit check for $JAVA_HOME environment variable.
   //
   // If it is defined and we are able to locate $JAVA_HOME/jre/lib/<arch>,
   // then we append a fake suffix "hotspot/libjvm[_g].so" to this path so
   // it looks like libjvm[_g].so is installed there
   // <JAVA_HOME>/jre/lib/<arch>/hotspot/libjvm[_g].so.
   //
   // Otherwise exit.
   //
   // Important note: if the location of libjvm.so changes this
   // code needs to be changed accordingly.
   // The next few definitions allow the code to be verbatim:
 #define malloc(n) (char*)NEW_C_HEAP_ARRAY(char, (n))
 #define getenv(n) ::getenv(n)
 /*
  * See ld(1):
  *      The linker uses the following search paths to locate required
  *      shared libraries:
  *        1: ...
  *        ...
  *        7: The default directories, normally /lib and /usr/lib.
  */
 #if defined(AMD64) || defined(_LP64) && (defined(SPARC) || defined(PPC) || defined(S390))
 #define DEFAULT_LIBPATH "/usr/lib64:/lib64:/lib:/usr/lib"
 #else
 #define DEFAULT_LIBPATH "/lib:/usr/lib"
 #endif
 #define EXTENSIONS_DIR  "/lib/ext"
 #define ENDORSED_DIR    "/lib/endorsed"
 #define REG_DIR         "/usr/java/packages"
   {
     /* sysclasspath, java_home, dll_dir */
     {
         char *home_path;
         char *dll_path;
         char *pslash;
         char buf[MAXPATHLEN];
         os::jvm_path(buf, sizeof(buf));
         // Found the full path to libjvm.so.
         // Now cut the path to <java_home>/jre if we can.
         *(strrchr(buf, '/')) = '\0';  /* get rid of /libjvm.so */
         pslash = strrchr(buf, '/');
         if (pslash != NULL)
             *pslash = '\0';           /* get rid of /{client|server|hotspot} */
         dll_path = malloc(strlen(buf) + 1);
         if (dll_path == NULL)
             return;
         strcpy(dll_path, buf);
         Arguments::set_dll_dir(dll_path);
         if (pslash != NULL) {
             pslash = strrchr(buf, '/');
             if (pslash != NULL) {
                 *pslash = '\0';       /* get rid of /<arch> */
                 pslash = strrchr(buf, '/');
                 if (pslash != NULL)
                     *pslash = '\0';   /* get rid of /lib */
             }
         }
         home_path = malloc(strlen(buf) + 1);
         if (home_path == NULL)
             return;
         strcpy(home_path, buf);
         Arguments::set_java_home(home_path);
         if (!set_boot_path('/', ':'))
             return;
     }
     /*
      * Where to look for native libraries
      *
      * Note: Due to a legacy implementation, most of the library path
      * is set in the launcher.  This was to accomodate linking restrictions
      * on legacy Linux implementations (which are no longer supported).
      * Eventually, all the library path setting will be done here.
      *
      * However, to prevent the proliferation of improperly built native
      * libraries, the new path component /usr/java/packages is added here.
      * Eventually, all the library path setting will be done here.
      */
     {
         char *ld_library_path;
         /*
          * Construct the invariant part of ld_library_path. Note that the
          * space for the colon and the trailing null are provided by the
          * nulls included by the sizeof operator (so actually we allocate
          * a byte more than necessary).
          */
         ld_library_path = (char *) malloc(sizeof(REG_DIR) + sizeof("/lib/") +
             strlen(cpu_arch) + sizeof(DEFAULT_LIBPATH));
         sprintf(ld_library_path, REG_DIR "/lib/%s:" DEFAULT_LIBPATH, cpu_arch);
         /*
          * Get the user setting of LD_LIBRARY_PATH, and prepended it.  It
          * should always exist (until the legacy problem cited above is
          * addressed).
          */
         char *v = getenv("LD_LIBRARY_PATH");
         if (v != NULL) {
             char *t = ld_library_path;
             /* That's +1 for the colon and +1 for the trailing '\0' */
             ld_library_path = (char *) malloc(strlen(v) + 1 + strlen(t) + 1);
             sprintf(ld_library_path, "%s:%s", v, t);
         }
         Arguments::set_library_path(ld_library_path);
     }
     /*
      * Extensions directories.
      *
      * Note that the space for the colon and the trailing null are provided
      * by the nulls included by the sizeof operator (so actually one byte more
      * than necessary is allocated).
      */
     {
         char *buf = malloc(strlen(Arguments::get_java_home()) +
             sizeof(EXTENSIONS_DIR) + sizeof(REG_DIR) + sizeof(EXTENSIONS_DIR));
         sprintf(buf, "%s" EXTENSIONS_DIR ":" REG_DIR EXTENSIONS_DIR,
             Arguments::get_java_home());
         Arguments::set_ext_dirs(buf);
     }
     /* Endorsed standards default directory. */
     {
         char * buf;
         buf = malloc(strlen(Arguments::get_java_home()) + sizeof(ENDORSED_DIR));
         sprintf(buf, "%s" ENDORSED_DIR, Arguments::get_java_home());
         Arguments::set_endorsed_dirs(buf);
     }
   }
 #undef malloc
 #undef getenv
 #undef EXTENSIONS_DIR
 #undef ENDORSED_DIR
   // Done
   return;
 }
 ////////////////////////////////////////////////////////////////////////////////
 // breakpoint support
 void os::breakpoint() {
   BREAKPOINT;
 }
 extern "C" void breakpoint() {
   // use debugger to set breakpoint here
 }
 ////////////////////////////////////////////////////////////////////////////////
 // signal support
 debug_only(static bool signal_sets_initialized = false);
 static sigset_t unblocked_sigs, vm_sigs, allowdebug_blocked_sigs;
 bool os::Linux::is_sig_ignored(int sig) {
       struct sigaction oact;
       sigaction(sig, (struct sigaction*)NULL, &oact);
       void* ohlr = oact.sa_sigaction ? CAST_FROM_FN_PTR(void*,  oact.sa_sigaction)
                                      : CAST_FROM_FN_PTR(void*,  oact.sa_handler);
       if (ohlr == CAST_FROM_FN_PTR(void*, SIG_IGN))
            return true;
       else
            return false;
 }
 void os::Linux::signal_sets_init() {
   // Should also have an assertion stating we are still single-threaded.
   assert(!signal_sets_initialized, "Already initialized");
   // Fill in signals that are necessarily unblocked for all threads in
   // the VM. Currently, we unblock the following signals:
   // SHUTDOWN{1,2,3}_SIGNAL: for shutdown hooks support (unless over-ridden
   //                         by -Xrs (=ReduceSignalUsage));
   // BREAK_SIGNAL which is unblocked only by the VM thread and blocked by all
   // other threads. The "ReduceSignalUsage" boolean tells us not to alter
   // the dispositions or masks wrt these signals.
   // Programs embedding the VM that want to use the above signals for their
   // own purposes must, at this time, use the "-Xrs" option to prevent
   // interference with shutdown hooks and BREAK_SIGNAL thread dumping.
   // (See bug 4345157, and other related bugs).
   // In reality, though, unblocking these signals is really a nop, since
   // these signals are not blocked by default.
   sigemptyset(&unblocked_sigs);
   sigemptyset(&allowdebug_blocked_sigs);
   sigaddset(&unblocked_sigs, SIGILL);
   sigaddset(&unblocked_sigs, SIGSEGV);
   sigaddset(&unblocked_sigs, SIGBUS);
   sigaddset(&unblocked_sigs, SIGFPE);
   sigaddset(&unblocked_sigs, SR_signum);
   if (!ReduceSignalUsage) {
    if (!os::Linux::is_sig_ignored(SHUTDOWN1_SIGNAL)) {
       sigaddset(&unblocked_sigs, SHUTDOWN1_SIGNAL);
       sigaddset(&allowdebug_blocked_sigs, SHUTDOWN1_SIGNAL);
    }
    if (!os::Linux::is_sig_ignored(SHUTDOWN2_SIGNAL)) {
       sigaddset(&unblocked_sigs, SHUTDOWN2_SIGNAL);
       sigaddset(&allowdebug_blocked_sigs, SHUTDOWN2_SIGNAL);
    }
    if (!os::Linux::is_sig_ignored(SHUTDOWN3_SIGNAL)) {
       sigaddset(&unblocked_sigs, SHUTDOWN3_SIGNAL);
       sigaddset(&allowdebug_blocked_sigs, SHUTDOWN3_SIGNAL);
    }
   }
   // Fill in signals that are blocked by all but the VM thread.
   sigemptyset(&vm_sigs);
   if (!ReduceSignalUsage)
     sigaddset(&vm_sigs, BREAK_SIGNAL);
   debug_only(signal_sets_initialized = true);
 }
 // These are signals that are unblocked while a thread is running Java.
 // (For some reason, they get blocked by default.)
 sigset_t* os::Linux::unblocked_signals() {
   assert(signal_sets_initialized, "Not initialized");
   return &unblocked_sigs;
 }
 // These are the signals that are blocked while a (non-VM) thread is
 // running Java. Only the VM thread handles these signals.
 sigset_t* os::Linux::vm_signals() {
   assert(signal_sets_initialized, "Not initialized");
   return &vm_sigs;
 }
 // These are signals that are blocked during cond_wait to allow debugger in
 sigset_t* os::Linux::allowdebug_blocked_signals() {
   assert(signal_sets_initialized, "Not initialized");
   return &allowdebug_blocked_sigs;
 }
 void os::Linux::hotspot_sigmask(Thread* thread) {
   //Save caller's signal mask before setting VM signal mask
   sigset_t caller_sigmask;
   pthread_sigmask(SIG_BLOCK, NULL, &caller_sigmask);
   OSThread* osthread = thread->osthread();
   osthread->set_caller_sigmask(caller_sigmask);
   pthread_sigmask(SIG_UNBLOCK, os::Linux::unblocked_signals(), NULL);
   if (!ReduceSignalUsage) {
     if (thread->is_VM_thread()) {
       // Only the VM thread handles BREAK_SIGNAL ...
       pthread_sigmask(SIG_UNBLOCK, vm_signals(), NULL);
     } else {
       // ... all other threads block BREAK_SIGNAL
       pthread_sigmask(SIG_BLOCK, vm_signals(), NULL);
     }
   }
 }
 //////////////////////////////////////////////////////////////////////////////
 // detecting pthread library
 void os::Linux::libpthread_init() {
   // Save glibc and pthread version strings. Note that _CS_GNU_LIBC_VERSION
   // and _CS_GNU_LIBPTHREAD_VERSION are supported in glibc >= 2.3.2. Use a
   // generic name for earlier versions.
   // Define macros here so we can build HotSpot on old systems.
 # ifndef _CS_GNU_LIBC_VERSION
 # define _CS_GNU_LIBC_VERSION 2
 # endif
 # ifndef _CS_GNU_LIBPTHREAD_VERSION
 # define _CS_GNU_LIBPTHREAD_VERSION 3
 # endif
   size_t n = confstr(_CS_GNU_LIBC_VERSION, NULL, 0);
   if (n > 0) {
      char *str = (char *)malloc(n);
      confstr(_CS_GNU_LIBC_VERSION, str, n);
      os::Linux::set_glibc_version(str);
   } else {
      // _CS_GNU_LIBC_VERSION is not supported, try gnu_get_libc_version()
      static char _gnu_libc_version[32];
      jio_snprintf(_gnu_libc_version, sizeof(_gnu_libc_version),
               "glibc %s %s", gnu_get_libc_version(), gnu_get_libc_release());
      os::Linux::set_glibc_version(_gnu_libc_version);
   }
   n = confstr(_CS_GNU_LIBPTHREAD_VERSION, NULL, 0);
   if (n > 0) {
      char *str = (char *)malloc(n);
      confstr(_CS_GNU_LIBPTHREAD_VERSION, str, n);
      // Vanilla RH-9 (glibc 2.3.2) has a bug that confstr() always tells
      // us "NPTL-0.29" even we are running with LinuxThreads. Check if this
      // is the case. LinuxThreads has a hard limit on max number of threads.
      // So sysconf(_SC_THREAD_THREADS_MAX) will return a positive value.
      // On the other hand, NPTL does not have such a limit, sysconf()
      // will return -1 and errno is not changed. Check if it is really NPTL.
      if (strcmp(os::Linux::glibc_version(), "glibc 2.3.2") == 0 &&
          strstr(str, "NPTL") &&
          sysconf(_SC_THREAD_THREADS_MAX) > 0) {
        free(str);
        os::Linux::set_libpthread_version("linuxthreads");
      } else {
        os::Linux::set_libpthread_version(str);
      }
   } else {
     // glibc before 2.3.2 only has LinuxThreads.
     os::Linux::set_libpthread_version("linuxthreads");
   }
   if (strstr(libpthread_version(), "NPTL")) {
      os::Linux::set_is_NPTL();
   } else {
      os::Linux::set_is_LinuxThreads();
   }
   // LinuxThreads have two flavors: floating-stack mode, which allows variable
   // stack size; and fixed-stack mode. NPTL is always floating-stack.
   if (os::Linux::is_NPTL() || os::Linux::supports_variable_stack_size()) {
      os::Linux::set_is_floating_stack();
   }
 }
 /////////////////////////////////////////////////////////////////////////////
 // thread stack
 // Force Linux kernel to expand current thread stack. If "bottom" is close
 // to the stack guard, caller should block all signals.
 //
 // MAP_GROWSDOWN:
 //   A special mmap() flag that is used to implement thread stacks. It tells
 //   kernel that the memory region should extend downwards when needed. This
 //   allows early versions of LinuxThreads to only mmap the first few pages
 //   when creating a new thread. Linux kernel will automatically expand thread
 //   stack as needed (on page faults).
 //
 //   However, because the memory region of a MAP_GROWSDOWN stack can grow on
 //   demand, if a page fault happens outside an already mapped MAP_GROWSDOWN
 //   region, it's hard to tell if the fault is due to a legitimate stack
 //   access or because of reading/writing non-exist memory (e.g. buffer
 //   overrun). As a rule, if the fault happens below current stack pointer,
 //   Linux kernel does not expand stack, instead a SIGSEGV is sent to the
 //   application (see Linux kernel fault.c).
 //
 //   This Linux feature can cause SIGSEGV when VM bangs thread stack for
 //   stack overflow detection.
 //
 //   Newer version of LinuxThreads (since glibc-2.2, or, RH-7.x) and NPTL do
 //   not use this flag. However, the stack of initial thread is not created
 //   by pthread, it is still MAP_GROWSDOWN. Also it's possible (though
 //   unlikely) that user code can create a thread with MAP_GROWSDOWN stack
 //   and then attach the thread to JVM.
 //
 // To get around the problem and allow stack banging on Linux, we need to
 // manually expand thread stack after receiving the SIGSEGV.
 //
 // There are two ways to expand thread stack to address "bottom", we used
 // both of them in JVM before 1.5:
 //   1. adjust stack pointer first so that it is below "bottom", and then
 //      touch "bottom"
 //   2. mmap() the page in question
 //
 // Now alternate signal stack is gone, it's harder to use 2. For instance,
 // if current sp is already near the lower end of page 101, and we need to
 // call mmap() to map page 100, it is possible that part of the mmap() frame
 // will be placed in page 100. When page 100 is mapped, it is zero-filled.
 // That will destroy the mmap() frame and cause VM to crash.
 //
 // The following code works by adjusting sp first, then accessing the "bottom"
 // page to force a page fault. Linux kernel will then automatically expand the
 // stack mapping.
 //
 // _expand_stack_to() assumes its frame size is less than page size, which
 // should always be true if the function is not inlined.
 #if __GNUC__ < 3    // gcc 2.x does not support noinline attribute
 #define NOINLINE
 #else
 #define NOINLINE __attribute__ ((noinline))
 #endif
 static void _expand_stack_to(address bottom) NOINLINE;
 static void _expand_stack_to(address bottom) {
   address sp;
   size_t size;
   volatile char *p;
   // Adjust bottom to point to the largest address within the same page, it
   // gives us a one-page buffer if alloca() allocates slightly more memory.
   bottom = (address)align_size_down((uintptr_t)bottom, os::Linux::page_size());
   bottom += os::Linux::page_size() - 1;
   // sp might be slightly above current stack pointer; if that's the case, we
   // will alloca() a little more space than necessary, which is OK. Don't use
   // os::current_stack_pointer(), as its result can be slightly below current
   // stack pointer, causing us to not alloca enough to reach "bottom".
   sp = (address)&sp;
   if (sp > bottom) {
     size = sp - bottom;
     p = (volatile char *)alloca(size);
     assert(p != NULL && p <= (volatile char *)bottom, "alloca problem?");
     p[0] = '\0';
   }
 }
 bool os::Linux::manually_expand_stack(JavaThread * t, address addr) {
   assert(t!=NULL, "just checking");
   assert(t->osthread()->expanding_stack(), "expand should be set");
   assert(t->stack_base() != NULL, "stack_base was not initialized");
   if (addr <  t->stack_base() && addr >= t->stack_yellow_zone_base()) {
     sigset_t mask_all, old_sigset;
     sigfillset(&mask_all);
     pthread_sigmask(SIG_SETMASK, &mask_all, &old_sigset);
     _expand_stack_to(addr);
     pthread_sigmask(SIG_SETMASK, &old_sigset, NULL);
     return true;
   }
   return false;
 }
 //////////////////////////////////////////////////////////////////////////////
 // create new thread
 static address highest_vm_reserved_address();
 // check if it's safe to start a new thread
 static bool _thread_safety_check(Thread* thread) {
   if (os::Linux::is_LinuxThreads() && !os::Linux::is_floating_stack()) {
     // Fixed stack LinuxThreads (SuSE Linux/x86, and some versions of Redhat)
     //   Heap is mmap'ed at lower end of memory space. Thread stacks are
     //   allocated (MAP_FIXED) from high address space. Every thread stack
     //   occupies a fixed size slot (usually 2Mbytes, but user can change
     //   it to other values if they rebuild LinuxThreads).
     //
     // Problem with MAP_FIXED is that mmap() can still succeed even part of
     // the memory region has already been mmap'ed. That means if we have too
     // many threads and/or very large heap, eventually thread stack will
     // collide with heap.
     //
     // Here we try to prevent heap/stack collision by comparing current
     // stack bottom with the highest address that has been mmap'ed by JVM
     // plus a safety margin for memory maps created by native code.
     //
     // This feature can be disabled by setting ThreadSafetyMargin to 0
     //
     if (ThreadSafetyMargin > 0) {
       address stack_bottom = os::current_stack_base() - os::current_stack_size();
       // not safe if our stack extends below the safety margin
       return stack_bottom - ThreadSafetyMargin >= highest_vm_reserved_address();
     } else {
       return true;
     }
   } else {
     // Floating stack LinuxThreads or NPTL:
     //   Unlike fixed stack LinuxThreads, thread stacks are not MAP_FIXED. When
     //   there's not enough space left, pthread_create() will fail. If we come
     //   here, that means enough space has been reserved for stack.
     return true;
   }
 }
 // Thread start routine for all newly created threads
 static void *java_start(Thread *thread) {
   // Try to randomize the cache line index of hot stack frames.
   // This helps when threads of the same stack traces evict each other's
   // cache lines. The threads can be either from the same JVM instance, or
   // from different JVM instances. The benefit is especially true for
   // processors with hyperthreading technology.
   static int counter = 0;
   int pid = os::current_process_id();
   alloca(((pid ^ counter++) & 7) * 128);
   ThreadLocalStorage::set_thread(thread);
   OSThread* osthread = thread->osthread();
   Monitor* sync = osthread->startThread_lock();
   // non floating stack LinuxThreads needs extra check, see above
   if (!_thread_safety_check(thread)) {
     // notify parent thread
     MutexLockerEx ml(sync, Mutex::_no_safepoint_check_flag);
     osthread->set_state(ZOMBIE);
     sync->notify_all();
     return NULL;
   }
   // thread_id is kernel thread id (similar to Solaris LWP id)
   osthread->set_thread_id(os::Linux::gettid());
   if (UseNUMA) {
     int lgrp_id = os::numa_get_group_id();
     if (lgrp_id != -1) {
       thread->set_lgrp_id(lgrp_id);
     }
   }
   // initialize signal mask for this thread
   os::Linux::hotspot_sigmask(thread);
   // initialize floating point control register
   os::Linux::init_thread_fpu_state();
   // handshaking with parent thread
   {
     MutexLockerEx ml(sync, Mutex::_no_safepoint_check_flag);
     // notify parent thread
     osthread->set_state(INITIALIZED);
     sync->notify_all();
     // wait until os::start_thread()
     while (osthread->get_state() == INITIALIZED) {
       sync->wait(Mutex::_no_safepoint_check_flag);
     }
   }
   // call one more level start routine
   thread->run();
   return 0;
 }
 bool os::create_thread(Thread* thread, ThreadType thr_type, size_t stack_size) {
   assert(thread->osthread() == NULL, "caller responsible");
   // Allocate the OSThread object
   OSThread* osthread = new OSThread(NULL, NULL);
   if (osthread == NULL) {
     return false;
   }
   // set the correct thread state
   osthread->set_thread_type(thr_type);
   // Initial state is ALLOCATED but not INITIALIZED
   osthread->set_state(ALLOCATED);
   thread->set_osthread(osthread);
   // init thread attributes
   pthread_attr_t attr;
   pthread_attr_init(&attr);
   pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
   // stack size
   if (os::Linux::supports_variable_stack_size()) {
     // calculate stack size if it's not specified by caller
     if (stack_size == 0) {
       stack_size = os::Linux::default_stack_size(thr_type);
       switch (thr_type) {
       case os::java_thread:
         // Java threads use ThreadStackSize which default value can be changed with the flag -Xss
         if (JavaThread::stack_size_at_create() > 0) stack_size = JavaThread::stack_size_at_create();
         break;
       case os::compiler_thread:
         if (CompilerThreadStackSize > 0) {
           stack_size = (size_t)(CompilerThreadStackSize * K);
           break;
         } // else fall through:
           // use VMThreadStackSize if CompilerThreadStackSize is not defined
       case os::vm_thread:
       case os::pgc_thread:
       case os::cgc_thread:
       case os::watcher_thread:
         if (VMThreadStackSize > 0) stack_size = (size_t)(VMThreadStackSize * K);
         break;
       }
     }
     stack_size = MAX2(stack_size, os::Linux::min_stack_allowed);
     pthread_attr_setstacksize(&attr, stack_size);
   } else {
     // let pthread_create() pick the default value.
   }
   // glibc guard page
   pthread_attr_setguardsize(&attr, os::Linux::default_guard_size(thr_type));
   ThreadState state;
   {
     // Serialize thread creation if we are running with fixed stack LinuxThreads
     bool lock = os::Linux::is_LinuxThreads() && !os::Linux::is_floating_stack();
     if (lock) {
       os::Linux::createThread_lock()->lock_without_safepoint_check();
     }
     pthread_t tid;
     int ret = pthread_create(&tid, &attr, (void* (*)(void*)) java_start, thread);
     pthread_attr_destroy(&attr);
     if (ret != 0) {
       if (PrintMiscellaneous && (Verbose || WizardMode)) {
         perror("pthread_create()");
       }
       // Need to clean up stuff we've allocated so far
       thread->set_osthread(NULL);
       delete osthread;
       if (lock) os::Linux::createThread_lock()->unlock();
       return false;
     }
     // Store pthread info into the OSThread
     osthread->set_pthread_id(tid);
     // Wait until child thread is either initialized or aborted
     {
       Monitor* sync_with_child = osthread->startThread_lock();
       MutexLockerEx ml(sync_with_child, Mutex::_no_safepoint_check_flag);
       while ((state = osthread->get_state()) == ALLOCATED) {
         sync_with_child->wait(Mutex::_no_safepoint_check_flag);
       }
     }
     if (lock) {
       os::Linux::createThread_lock()->unlock();
     }
   }
   // Aborted due to thread limit being reached
   if (state == ZOMBIE) {
       thread->set_osthread(NULL);
       delete osthread;
       return false;
   }
   // The thread is returned suspended (in state INITIALIZED),
   // and is started higher up in the call chain
   assert(state == INITIALIZED, "race condition");
   return true;
 }
 /////////////////////////////////////////////////////////////////////////////
 // attach existing thread
 // bootstrap the main thread
 bool os::create_main_thread(JavaThread* thread) {
   assert(os::Linux::_main_thread == pthread_self(), "should be called inside main thread");
   return create_attached_thread(thread);
 }
 bool os::create_attached_thread(JavaThread* thread) {
 #ifdef ASSERT
     thread->verify_not_published();
 #endif
   // Allocate the OSThread object
   OSThread* osthread = new OSThread(NULL, NULL);
   if (osthread == NULL) {
     return false;
   }
   // Store pthread info into the OSThread
   osthread->set_thread_id(os::Linux::gettid());
   osthread->set_pthread_id(::pthread_self());
   // initialize floating point control register
   os::Linux::init_thread_fpu_state();
   // Initial thread state is RUNNABLE
   osthread->set_state(RUNNABLE);
   thread->set_osthread(osthread);
   if (UseNUMA) {
     int lgrp_id = os::numa_get_group_id();
     if (lgrp_id != -1) {
       thread->set_lgrp_id(lgrp_id);
     }
   }
   if (os::Linux::is_initial_thread()) {
     // If current thread is initial thread, its stack is mapped on demand,
     // see notes about MAP_GROWSDOWN. Here we try to force kernel to map
     // the entire stack region to avoid SEGV in stack banging.
     // It is also useful to get around the heap-stack-gap problem on SuSE
     // kernel (see 4821821 for details). We first expand stack to the top
     // of yellow zone, then enable stack yellow zone (order is significant,
     // enabling yellow zone first will crash JVM on SuSE Linux), so there
     // is no gap between the last two virtual memory regions.
     JavaThread *jt = (JavaThread *)thread;
     address addr = jt->stack_yellow_zone_base();
     assert(addr != NULL, "initialization problem?");
     assert(jt->stack_available(addr) > 0, "stack guard should not be enabled");
     osthread->set_expanding_stack();
     os::Linux::manually_expand_stack(jt, addr);
     osthread->clear_expanding_stack();
   }
   // initialize signal mask for this thread
   // and save the caller's signal mask
   os::Linux::hotspot_sigmask(thread);
   return true;
 }
 void os::pd_start_thread(Thread* thread) {
   OSThread * osthread = thread->osthread();
   assert(osthread->get_state() != INITIALIZED, "just checking");
   Monitor* sync_with_child = osthread->startThread_lock();
   MutexLockerEx ml(sync_with_child, Mutex::_no_safepoint_check_flag);
   sync_with_child->notify();
 }
 // Free Linux resources related to the OSThread
 void os::free_thread(OSThread* osthread) {
   assert(osthread != NULL, "osthread not set");
   if (Thread::current()->osthread() == osthread) {
     // Restore caller's signal mask
     sigset_t sigmask = osthread->caller_sigmask();
     pthread_sigmask(SIG_SETMASK, &sigmask, NULL);
    }
   delete osthread;
 }
 //////////////////////////////////////////////////////////////////////////////
 // thread local storage
 int os::allocate_thread_local_storage() {
   pthread_key_t key;
   int rslt = pthread_key_create(&key, NULL);
   assert(rslt == 0, "cannot allocate thread local storage");
   return (int)key;
 }
 // Note: This is currently not used by VM, as we don't destroy TLS key
 // on VM exit.
 void os::free_thread_local_storage(int index) {
   int rslt = pthread_key_delete((pthread_key_t)index);
   assert(rslt == 0, "invalid index");
 }
 void os::thread_local_storage_at_put(int index, void* value) {
   int rslt = pthread_setspecific((pthread_key_t)index, value);
   assert(rslt == 0, "pthread_setspecific failed");
 }
 extern "C" Thread* get_thread() {
   return ThreadLocalStorage::thread();
 }
 //////////////////////////////////////////////////////////////////////////////
 // initial thread
 // Check if current thread is the initial thread, similar to Solaris thr_main.
 bool os::Linux::is_initial_thread(void) {
   char dummy;
   // If called before init complete, thread stack bottom will be null.
   // Can be called if fatal error occurs before initialization.
   if (initial_thread_stack_bottom() == NULL) return false;
   assert(initial_thread_stack_bottom() != NULL &&
          initial_thread_stack_size()   != 0,
          "os::init did not locate initial thread's stack region");
   if ((address)&dummy >= initial_thread_stack_bottom() &&
       (address)&dummy < initial_thread_stack_bottom() + initial_thread_stack_size())
        return true;
   else return false;
 }
 // Find the virtual memory area that contains addr
 static bool find_vma(address addr, address* vma_low, address* vma_high) {
   FILE *fp = fopen("/proc/self/maps", "r");
   if (fp) {
     address low, high;
     while (!feof(fp)) {
       if (fscanf(fp, "%p-%p", &low, &high) == 2) {
         if (low <= addr && addr < high) {
            if (vma_low)  *vma_low  = low;
            if (vma_high) *vma_high = high;
            fclose (fp);
            return true;
         }
       }
       for (;;) {
         int ch = fgetc(fp);
         if (ch == EOF || ch == (int)'\n') break;
       }
     }
     fclose(fp);
   }
   return false;
 }
 // Locate initial thread stack. This special handling of initial thread stack
 // is needed because pthread_getattr_np() on most (all?) Linux distros returns
 // bogus value for initial thread.
 void os::Linux::capture_initial_stack(size_t max_size) {
   // stack size is the easy part, get it from RLIMIT_STACK
   size_t stack_size;
   struct rlimit rlim;
   getrlimit(RLIMIT_STACK, &rlim);
   stack_size = rlim.rlim_cur;
   // 6308388: a bug in ld.so will relocate its own .data section to the
   //   lower end of primordial stack; reduce ulimit -s value a little bit
   //   so we won't install guard page on ld.so's data section.
   stack_size -= 2 * page_size();
   // 4441425: avoid crash with "unlimited" stack size on SuSE 7.1 or Redhat
   //   7.1, in both cases we will get 2G in return value.
   // 4466587: glibc 2.2.x compiled w/o "--enable-kernel=2.4.0" (RH 7.0,
   //   SuSE 7.2, Debian) can not handle alternate signal stack correctly
   //   for initial thread if its stack size exceeds 6M. Cap it at 2M,
   //   in case other parts in glibc still assumes 2M max stack size.
   // FIXME: alt signal stack is gone, maybe we can relax this constraint?
 #ifndef IA64
   if (stack_size > 2 * K * K) stack_size = 2 * K * K;
 #else
   // Problem still exists RH7.2 (IA64 anyway) but 2MB is a little small
   if (stack_size > 4 * K * K) stack_size = 4 * K * K;
 #endif
   // Try to figure out where the stack base (top) is. This is harder.
   //
   // When an application is started, glibc saves the initial stack pointer in
   // a global variable "__libc_stack_end", which is then used by system
   // libraries. __libc_stack_end should be pretty close to stack top. The
   // variable is available since the very early days. However, because it is
   // a private interface, it could disappear in the future.
   //
   // Linux kernel saves start_stack information in /proc/<pid>/stat. Similar
   // to __libc_stack_end, it is very close to stack top, but isn't the real
   // stack top. Note that /proc may not exist if VM is running as a chroot
   // program, so reading /proc/<pid>/stat could fail. Also the contents of
   // /proc/<pid>/stat could change in the future (though unlikely).
   //
   // We try __libc_stack_end first. If that doesn't work, look for
   // /proc/<pid>/stat. If neither of them works, we use current stack pointer
   // as a hint, which should work well in most cases.
   uintptr_t stack_start;
   // try __libc_stack_end first
   uintptr_t *p = (uintptr_t *)dlsym(RTLD_DEFAULT, "__libc_stack_end");
   if (p && *p) {
     stack_start = *p;
   } else {
     // see if we can get the start_stack field from /proc/self/stat
     FILE *fp;
     int pid;
     char state;
     int ppid;
     int pgrp;
     int session;
     int nr;
     int tpgrp;
     unsigned long flags;
     unsigned long minflt;
     unsigned long cminflt;
     unsigned long majflt;
     unsigned long cmajflt;
     unsigned long utime;
     unsigned long stime;
     long cutime;
     long cstime;
     long prio;
     long nice;
     long junk;
     long it_real;
     uintptr_t start;
     uintptr_t vsize;
     intptr_t rss;
     uintptr_t rsslim;
     uintptr_t scodes;
     uintptr_t ecode;
     int i;
     // Figure what the primordial thread stack base is. Code is inspired
     // by email from Hans Boehm. /proc/self/stat begins with current pid,
     // followed by command name surrounded by parentheses, state, etc.
     char stat[2048];
     int statlen;
     fp = fopen("/proc/self/stat", "r");
     if (fp) {
       statlen = fread(stat, 1, 2047, fp);
       stat[statlen] = '\0';
       fclose(fp);
       // Skip pid and the command string. Note that we could be dealing with
       // weird command names, e.g. user could decide to rename java launcher
       // to "java 1.4.2 :)", then the stat file would look like
       //                1234 (java 1.4.2 :)) R ... ...
       // We don't really need to know the command string, just find the last
       // occurrence of ")" and then start parsing from there. See bug 4726580.
       char * s = strrchr(stat, ')');
       i = 0;
       if (s) {
         // Skip blank chars
         do s++; while (isspace(*s));
 #define _UFM UINTX_FORMAT
 #define _DFM INTX_FORMAT
         /*                                     1   1   1   1   1   1   1   1   1   1   2   2    2    2    2    2    2    2    2 */
         /*              3  4  5  6  7  8   9   0   1   2   3   4   5   6   7   8   9   0   1    2    3    4    5    6    7    8 */
         i = sscanf(s, "%c %d %d %d %d %d %lu %lu %lu %lu %lu %lu %lu %ld %ld %ld %ld %ld %ld " _UFM _UFM _DFM _UFM _UFM _UFM _UFM,
              &state,          /* 3  %c  */
              &ppid,           /* 4  %d  */
              &pgrp,           /* 5  %d  */
              &session,        /* 6  %d  */
              &nr,             /* 7  %d  */
              &tpgrp,          /* 8  %d  */
              &flags,          /* 9  %lu  */
              &minflt,         /* 10 %lu  */
              &cminflt,        /* 11 %lu  */
              &majflt,         /* 12 %lu  */
              &cmajflt,        /* 13 %lu  */
              &utime,          /* 14 %lu  */
              &stime,          /* 15 %lu  */
              &cutime,         /* 16 %ld  */
              &cstime,         /* 17 %ld  */
              &prio,           /* 18 %ld  */
              &nice,           /* 19 %ld  */
              &junk,           /* 20 %ld  */
              &it_real,        /* 21 %ld  */
              &start,          /* 22 UINTX_FORMAT */
              &vsize,          /* 23 UINTX_FORMAT */
              &rss,            /* 24 INTX_FORMAT  */
              &rsslim,         /* 25 UINTX_FORMAT */
              &scodes,         /* 26 UINTX_FORMAT */
              &ecode,          /* 27 UINTX_FORMAT */
              &stack_start);   /* 28 UINTX_FORMAT */
       }
 #undef _UFM
 #undef _DFM
       if (i != 28 - 2) {
          assert(false, "Bad conversion from /proc/self/stat");
          // product mode - assume we are the initial thread, good luck in the
          // embedded case.
          warning("Can't detect initial thread stack location - bad conversion");
          stack_start = (uintptr_t) &rlim;
       }
     } else {
       // For some reason we can't open /proc/self/stat (for example, running on
       // FreeBSD with a Linux emulator, or inside chroot), this should work for
       // most cases, so don't abort:
       warning("Can't detect initial thread stack location - no /proc/self/stat");
       stack_start = (uintptr_t) &rlim;
     }
   }
   // Now we have a pointer (stack_start) very close to the stack top, the
   // next thing to do is to figure out the exact location of stack top. We
   // can find out the virtual memory area that contains stack_start by
   // reading /proc/self/maps, it should be the last vma in /proc/self/maps,
   // and its upper limit is the real stack top. (again, this would fail if
   // running inside chroot, because /proc may not exist.)
   uintptr_t stack_top;
   address low, high;
   if (find_vma((address)stack_start, &low, &high)) {
     // success, "high" is the true stack top. (ignore "low", because initial
     // thread stack grows on demand, its real bottom is high - RLIMIT_STACK.)
     stack_top = (uintptr_t)high;
   } else {
     // failed, likely because /proc/self/maps does not exist
     warning("Can't detect initial thread stack location - find_vma failed");
     // best effort: stack_start is normally within a few pages below the real
     // stack top, use it as stack top, and reduce stack size so we won't put
     // guard page outside stack.
     stack_top = stack_start;
     stack_size -= 16 * page_size();
   }
   // stack_top could be partially down the page so align it
   stack_top = align_size_up(stack_top, page_size());
   if (max_size && stack_size > max_size) {
      _initial_thread_stack_size = max_size;
   } else {
      _initial_thread_stack_size = stack_size;
   }
   _initial_thread_stack_size = align_size_down(_initial_thread_stack_size, page_size());
   _initial_thread_stack_bottom = (address)stack_top - _initial_thread_stack_size;
 }
 ////////////////////////////////////////////////////////////////////////////////
 // time support
 // Time since start-up in seconds to a fine granularity.
 // Used by VMSelfDestructTimer and the MemProfiler.
 double os::elapsedTime() {
   return (double)(os::elapsed_counter()) * 0.000001;
 }
 jlong os::elapsed_counter() {
   timeval time;
   int status = gettimeofday(&time, NULL);
   return jlong(time.tv_sec) * 1000 * 1000 + jlong(time.tv_usec) - initial_time_count;
 }
 jlong os::elapsed_frequency() {
   return (1000 * 1000);
 }
 // For now, we say that linux does not support vtime.  I have no idea
 // whether it can actually be made to (DLD, 9/13/05).
 bool os::supports_vtime() { return false; }
 bool os::enable_vtime()   { return false; }
 bool os::vtime_enabled()  { return false; }
 double os::elapsedVTime() {
   // better than nothing, but not much
   return elapsedTime();
 }
 jlong os::javaTimeMillis() {
   timeval time;
   int status = gettimeofday(&time, NULL);
   assert(status != -1, "linux error");
   return jlong(time.tv_sec) * 1000  +  jlong(time.tv_usec / 1000);
 }
 #ifndef CLOCK_MONOTONIC
 #define CLOCK_MONOTONIC (1)
 #endif
 void os::Linux::clock_init() {
   // we do dlopen's in this particular order due to bug in linux
   // dynamical loader (see 6348968) leading to crash on exit
   void* handle = dlopen("librt.so.1", RTLD_LAZY);
   if (handle == NULL) {
     handle = dlopen("librt.so", RTLD_LAZY);
   }
   if (handle) {
     int (*clock_getres_func)(clockid_t, struct timespec*) =
            (int(*)(clockid_t, struct timespec*))dlsym(handle, "clock_getres");
     int (*clock_gettime_func)(clockid_t, struct timespec*) =
            (int(*)(clockid_t, struct timespec*))dlsym(handle, "clock_gettime");
     if (clock_getres_func && clock_gettime_func) {
       // See if monotonic clock is supported by the kernel. Note that some
       // early implementations simply return kernel jiffies (updated every
       // 1/100 or 1/1000 second). It would be bad to use such a low res clock
       // for nano time (though the monotonic property is still nice to have).
       // It's fixed in newer kernels, however clock_getres() still returns
       // 1/HZ. We check if clock_getres() works, but will ignore its reported
       // resolution for now. Hopefully as people move to new kernels, this
       // won't be a problem.
       struct timespec res;
       struct timespec tp;
       if (clock_getres_func (CLOCK_MONOTONIC, &res) == 0 &&
           clock_gettime_func(CLOCK_MONOTONIC, &tp)  == 0) {
         // yes, monotonic clock is supported
         _clock_gettime = clock_gettime_func;
       } else {
         // close librt if there is no monotonic clock
         dlclose(handle);
       }
     }
   }
 }
 #ifndef SYS_clock_getres
 #if defined(IA32) || defined(AMD64)
 #define SYS_clock_getres IA32_ONLY(266)  AMD64_ONLY(229)
 #define sys_clock_getres(x,y)  ::syscall(SYS_clock_getres, x, y)
 #else
 #warning "SYS_clock_getres not defined for this platform, disabling fast_thread_cpu_time"
 #define sys_clock_getres(x,y)  -1
 #endif
 #else
 #define sys_clock_getres(x,y)  ::syscall(SYS_clock_getres, x, y)
 #endif
 void os::Linux::fast_thread_clock_init() {
   if (!UseLinuxPosixThreadCPUClocks) {
     return;
   }
   clockid_t clockid;
   struct timespec tp;
   int (*pthread_getcpuclockid_func)(pthread_t, clockid_t *) =
       (int(*)(pthread_t, clockid_t *)) dlsym(RTLD_DEFAULT, "pthread_getcpuclockid");
   // Switch to using fast clocks for thread cpu time if
   // the sys_clock_getres() returns 0 error code.
   // Note, that some kernels may support the current thread
   // clock (CLOCK_THREAD_CPUTIME_ID) but not the clocks
   // returned by the pthread_getcpuclockid().
   // If the fast Posix clocks are supported then the sys_clock_getres()
   // must return at least tp.tv_sec == 0 which means a resolution
   // better than 1 sec. This is extra check for reliability.
   if(pthread_getcpuclockid_func &&
      pthread_getcpuclockid_func(_main_thread, &clockid) == 0 &&
      sys_clock_getres(clockid, &tp) == 0 && tp.tv_sec == 0) {
     _supports_fast_thread_cpu_time = true;
     _pthread_getcpuclockid = pthread_getcpuclockid_func;
   }
 }
 jlong os::javaTimeNanos() {
   if (Linux::supports_monotonic_clock()) {
     struct timespec tp;
     int status = Linux::clock_gettime(CLOCK_MONOTONIC, &tp);
     assert(status == 0, "gettime error");
     jlong result = jlong(tp.tv_sec) * (1000 * 1000 * 1000) + jlong(tp.tv_nsec);
     return result;
   } else {
     timeval time;
     int status = gettimeofday(&time, NULL);
     assert(status != -1, "linux error");
     jlong usecs = jlong(time.tv_sec) * (1000 * 1000) + jlong(time.tv_usec);
     return 1000 * usecs;
   }
 }
 void os::javaTimeNanos_info(jvmtiTimerInfo *info_ptr) {
   if (Linux::supports_monotonic_clock()) {
     info_ptr->max_value = ALL_64_BITS;
     // CLOCK_MONOTONIC - amount of time since some arbitrary point in the past
     info_ptr->may_skip_backward = false;      // not subject to resetting or drifting
     info_ptr->may_skip_forward = false;       // not subject to resetting or drifting
   } else {
     // gettimeofday - based on time in seconds since the Epoch thus does not wrap
     info_ptr->max_value = ALL_64_BITS;
     // gettimeofday is a real time clock so it skips
     info_ptr->may_skip_backward = true;
     info_ptr->may_skip_forward = true;
   }
   info_ptr->kind = JVMTI_TIMER_ELAPSED;                // elapsed not CPU time
 }
 // Return the real, user, and system times in seconds from an
 // arbitrary fixed point in the past.
 bool os::getTimesSecs(double* process_real_time,
                       double* process_user_time,
                       double* process_system_time) {
   struct tms ticks;
   clock_t real_ticks = times(&ticks);
   if (real_ticks == (clock_t) (-1)) {
     return false;
   } else {
     double ticks_per_second = (double) clock_tics_per_sec;
     *process_user_time = ((double) ticks.tms_utime) / ticks_per_second;
     *process_system_time = ((double) ticks.tms_stime) / ticks_per_second;
     *process_real_time = ((double) real_ticks) / ticks_per_second;
     return true;
   }
 }
 char * os::local_time_string(char *buf, size_t buflen) {
   struct tm t;
   time_t long_time;
   time(&long_time);
   localtime_r(&long_time, &t);
   jio_snprintf(buf, buflen, "%d-%02d-%02d %02d:%02d:%02d",
                t.tm_year + 1900, t.tm_mon + 1, t.tm_mday,
                t.tm_hour, t.tm_min, t.tm_sec);
   return buf;
 }
 struct tm* os::localtime_pd(const time_t* clock, struct tm*  res) {
   return localtime_r(clock, res);
 }
 ////////////////////////////////////////////////////////////////////////////////
 // runtime exit support
 // Note: os::shutdown() might be called very early during initialization, or
 // called from signal handler. Before adding something to os::shutdown(), make
 // sure it is async-safe and can handle partially initialized VM.
 void os::shutdown() {
   // allow PerfMemory to attempt cleanup of any persistent resources
   perfMemory_exit();
   // needs to remove object in file system
   AttachListener::abort();
   // flush buffered output, finish log files
   ostream_abort();
   // Check for abort hook
   abort_hook_t abort_hook = Arguments::abort_hook();
   if (abort_hook != NULL) {
     abort_hook();
   }
 }
 // Note: os::abort() might be called very early during initialization, or
 // called from signal handler. Before adding something to os::abort(), make
 // sure it is async-safe and can handle partially initialized VM.
 void os::abort(bool dump_core) {
   os::shutdown();
   if (dump_core) {
 #ifndef PRODUCT
     fdStream out(defaultStream::output_fd());
     out.print_raw("Current thread is ");
     char buf[16];
     jio_snprintf(buf, sizeof(buf), UINTX_FORMAT, os::current_thread_id());
     out.print_raw_cr(buf);
     out.print_raw_cr("Dumping core ...");
 #endif
     ::abort(); // dump core
   }
   ::exit(1);
 }
 // Die immediately, no exit hook, no abort hook, no cleanup.
 void os::die() {
   // _exit() on LinuxThreads only kills current thread
   ::abort();
 }
 // unused on linux for now.
 void os::set_error_file(const char *logfile) {}
 intx os::current_thread_id() { return (intx)pthread_self(); }
 int os::current_process_id() {
   // Under the old linux thread library, linux gives each thread
   // its own process id. Because of this each thread will return
   // a different pid if this method were to return the result
   // of getpid(2). Linux provides no api that returns the pid
   // of the launcher thread for the vm. This implementation
   // returns a unique pid, the pid of the launcher thread
   // that starts the vm 'process'.
   // Under the NPTL, getpid() returns the same pid as the
   // launcher thread rather than a unique pid per thread.
   // Use gettid() if you want the old pre NPTL behaviour.
   // if you are looking for the result of a call to getpid() that
   // returns a unique pid for the calling thread, then look at the
   // OSThread::thread_id() method in osThread_linux.hpp file
   return (int)(_initial_pid ? _initial_pid : getpid());
 }
 // DLL functions
 const char* os::dll_file_extension() { return ".so"; }
 const char* os::get_temp_directory() {
   const char *prop = Arguments::get_property("java.io.tmpdir");
   return prop == NULL ? "/tmp" : prop;
 }
 static bool file_exists(const char* filename) {
   struct stat statbuf;
   if (filename == NULL || strlen(filename) == 0) {
     return false;
   }
   return os::stat(filename, &statbuf) == 0;
 }
 void os::dll_build_name(char* buffer, size_t buflen,
                         const char* pname, const char* fname) {
   // Copied from libhpi
   const size_t pnamelen = pname ? strlen(pname) : 0;
   // Quietly truncate on buffer overflow.  Should be an error.
   if (pnamelen + strlen(fname) + 10 > (size_t) buflen) {
       *buffer = '\0';
       return;
   }
   if (pnamelen == 0) {
     snprintf(buffer, buflen, "lib%s.so", fname);
   } else if (strchr(pname, *os::path_separator()) != NULL) {
     int n;
     char** pelements = split_path(pname, &n);
     for (int i = 0 ; i < n ; i++) {
       // Really shouldn't be NULL, but check can't hurt
       if (pelements[i] == NULL || strlen(pelements[i]) == 0) {
         continue; // skip the empty path values
       }
       snprintf(buffer, buflen, "%s/lib%s.so", pelements[i], fname);
       if (file_exists(buffer)) {
         break;
       }
     }
     // release the storage
     for (int i = 0 ; i < n ; i++) {
       if (pelements[i] != NULL) {
         FREE_C_HEAP_ARRAY(char, pelements[i]);
       }
     }
     if (pelements != NULL) {
       FREE_C_HEAP_ARRAY(char*, pelements);
     }
   } else {
     snprintf(buffer, buflen, "%s/lib%s.so", pname, fname);
   }
 }
 const char* os::get_current_directory(char *buf, int buflen) {
   return getcwd(buf, buflen);
 }
 // check if addr is inside libjvm[_g].so
 bool os::address_is_in_vm(address addr) {
   static address libjvm_base_addr;
   Dl_info dlinfo;
   if (libjvm_base_addr == NULL) {
     dladdr(CAST_FROM_FN_PTR(void *, os::address_is_in_vm), &dlinfo);
     libjvm_base_addr = (address)dlinfo.dli_fbase;
     assert(libjvm_base_addr !=NULL, "Cannot obtain base address for libjvm");
   }
   if (dladdr((void *)addr, &dlinfo)) {
     if (libjvm_base_addr == (address)dlinfo.dli_fbase) return true;
   }
   return false;
 }
 bool os::dll_address_to_function_name(address addr, char *buf,
                                       int buflen, int *offset) {
   Dl_info dlinfo;
   if (dladdr((void*)addr, &dlinfo) && dlinfo.dli_sname != NULL) {
     if (buf) jio_snprintf(buf, buflen, "%s", dlinfo.dli_sname);
     if (offset) *offset = addr - (address)dlinfo.dli_saddr;
     return true;
   } else {
     if (buf) buf[0] = '\0';
     if (offset) *offset = -1;
     return false;
   }
 }
 struct _address_to_library_name {
   address addr;          // input : memory address
   size_t  buflen;        //         size of fname
   char*   fname;         // output: library name
   address base;          //         library base addr
 };
 static int address_to_library_name_callback(struct dl_phdr_info *info,
                                             size_t size, void *data) {
   int i;
   bool found = false;
   address libbase = NULL;
   struct _address_to_library_name * d = (struct _address_to_library_name *)data;
   // iterate through all loadable segments
   for (i = 0; i < info->dlpi_phnum; i++) {
     address segbase = (address)(info->dlpi_addr + info->dlpi_phdr[i].p_vaddr);
     if (info->dlpi_phdr[i].p_type == PT_LOAD) {
       // base address of a library is the lowest address of its loaded
       // segments.
       if (libbase == NULL || libbase > segbase) {
         libbase = segbase;
       }
       // see if 'addr' is within current segment
       if (segbase <= d->addr &&
           d->addr < segbase + info->dlpi_phdr[i].p_memsz) {
         found = true;
       }
     }
   }
   // dlpi_name is NULL or empty if the ELF file is executable, return 0
   // so dll_address_to_library_name() can fall through to use dladdr() which
   // can figure out executable name from argv[0].
   if (found && info->dlpi_name && info->dlpi_name[0]) {
     d->base = libbase;
     if (d->fname) {
       jio_snprintf(d->fname, d->buflen, "%s", info->dlpi_name);
     }
     return 1;
   }
   return 0;
 }
 bool os::dll_address_to_library_name(address addr, char* buf,
                                      int buflen, int* offset) {
   Dl_info dlinfo;
   struct _address_to_library_name data;
   // There is a bug in old glibc dladdr() implementation that it could resolve
   // to wrong library name if the .so file has a base address != NULL. Here
   // we iterate through the program headers of all loaded libraries to find
   // out which library 'addr' really belongs to. This workaround can be
   // removed once the minimum requirement for glibc is moved to 2.3.x.
   data.addr = addr;
   data.fname = buf;
   data.buflen = buflen;
   data.base = NULL;
   int rslt = dl_iterate_phdr(address_to_library_name_callback, (void *)&data);
   if (rslt) {
      // buf already contains library name
      if (offset) *offset = addr - data.base;
      return true;
   } else if (dladdr((void*)addr, &dlinfo)){
      if (buf) jio_snprintf(buf, buflen, "%s", dlinfo.dli_fname);
      if (offset) *offset = addr - (address)dlinfo.dli_fbase;
      return true;
   } else {
      if (buf) buf[0] = '\0';
      if (offset) *offset = -1;
      return false;
   }
 }
   // Loads .dll/.so and
   // in case of error it checks if .dll/.so was built for the
   // same architecture as Hotspot is running on
 void * os::dll_load(const char *filename, char *ebuf, int ebuflen)
 {
   void * result= ::dlopen(filename, RTLD_LAZY);
   if (result != NULL) {
     // Successful loading
     return result;
   }
   Elf32_Ehdr elf_head;
   // Read system error message into ebuf
   // It may or may not be overwritten below
   ::strncpy(ebuf, ::dlerror(), ebuflen-1);
   ebuf[ebuflen-1]='\0';
   int diag_msg_max_length=ebuflen-strlen(ebuf);
   char* diag_msg_buf=ebuf+strlen(ebuf);
   if (diag_msg_max_length==0) {
     // No more space in ebuf for additional diagnostics message
     return NULL;
   }
   int file_descriptor= ::open(filename, O_RDONLY | O_NONBLOCK);
   if (file_descriptor < 0) {
     // Can't open library, report dlerror() message
     return NULL;
   }
   bool failed_to_read_elf_head=
     (sizeof(elf_head)!=
         (::read(file_descriptor, &elf_head,sizeof(elf_head)))) ;
   ::close(file_descriptor);
   if (failed_to_read_elf_head) {
     // file i/o error - report dlerror() msg
     return NULL;
   }
   typedef struct {
     Elf32_Half  code;         // Actual value as defined in elf.h
     Elf32_Half  compat_class; // Compatibility of archs at VM's sense
     char        elf_class;    // 32 or 64 bit
     char        endianess;    // MSB or LSB
     char*       name;         // String representation
   } arch_t;
   #ifndef EM_486
   #define EM_486          6               /* Intel 80486 */
   #endif
   static const arch_t arch_array[]={
     {EM_386,         EM_386,     ELFCLASS32, ELFDATA2LSB, (char*)"IA 32"},
     {EM_486,         EM_386,     ELFCLASS32, ELFDATA2LSB, (char*)"IA 32"},
     {EM_IA_64,       EM_IA_64,   ELFCLASS64, ELFDATA2LSB, (char*)"IA 64"},
     {EM_X86_64,      EM_X86_64,  ELFCLASS64, ELFDATA2LSB, (char*)"AMD 64"},
     {EM_SPARC,       EM_SPARC,   ELFCLASS32, ELFDATA2MSB, (char*)"Sparc 32"},
     {EM_SPARC32PLUS, EM_SPARC,   ELFCLASS32, ELFDATA2MSB, (char*)"Sparc 32"},
     {EM_SPARCV9,     EM_SPARCV9, ELFCLASS64, ELFDATA2MSB, (char*)"Sparc v9 64"},
     {EM_PPC,         EM_PPC,     ELFCLASS32, ELFDATA2MSB, (char*)"Power PC 32"},
     {EM_PPC64,       EM_PPC64,   ELFCLASS64, ELFDATA2MSB, (char*)"Power PC 64"},
     {EM_ARM,         EM_ARM,     ELFCLASS32,   ELFDATA2LSB, (char*)"ARM"},
     {EM_S390,        EM_S390,    ELFCLASSNONE, ELFDATA2MSB, (char*)"IBM System/390"},
     {EM_ALPHA,       EM_ALPHA,   ELFCLASS64, ELFDATA2LSB, (char*)"Alpha"},
     {EM_MIPS_RS3_LE, EM_MIPS_RS3_LE, ELFCLASS32, ELFDATA2LSB, (char*)"MIPSel"},
     {EM_MIPS,        EM_MIPS,    ELFCLASS32, ELFDATA2MSB, (char*)"MIPS"},
     {EM_PARISC,      EM_PARISC,  ELFCLASS32, ELFDATA2MSB, (char*)"PARISC"},
     {EM_68K,         EM_68K,     ELFCLASS32, ELFDATA2MSB, (char*)"M68k"}
   };
   #if  (defined IA32)
     static  Elf32_Half running_arch_code=EM_386;
   #elif   (defined AMD64)
     static  Elf32_Half running_arch_code=EM_X86_64;
   #elif  (defined IA64)
     static  Elf32_Half running_arch_code=EM_IA_64;
   #elif  (defined __sparc) && (defined _LP64)
     static  Elf32_Half running_arch_code=EM_SPARCV9;
   #elif  (defined __sparc) && (!defined _LP64)
     static  Elf32_Half running_arch_code=EM_SPARC;
   #elif  (defined __powerpc64__)
     static  Elf32_Half running_arch_code=EM_PPC64;
   #elif  (defined __powerpc__)
     static  Elf32_Half running_arch_code=EM_PPC;
   #elif  (defined ARM)
     static  Elf32_Half running_arch_code=EM_ARM;
   #elif  (defined S390)
     static  Elf32_Half running_arch_code=EM_S390;
   #elif  (defined ALPHA)
     static  Elf32_Half running_arch_code=EM_ALPHA;
   #elif  (defined MIPSEL)
     static  Elf32_Half running_arch_code=EM_MIPS_RS3_LE;
   #elif  (defined PARISC)
     static  Elf32_Half running_arch_code=EM_PARISC;
   #elif  (defined MIPS)
     static  Elf32_Half running_arch_code=EM_MIPS;
   #elif  (defined M68K)
     static  Elf32_Half running_arch_code=EM_68K;
   #else
     #error Method os::dll_load requires that one of following is defined:\
          IA32, AMD64, IA64, __sparc, __powerpc__, ARM, S390, ALPHA, MIPS, MIPSEL, PARISC, M68K
   #endif
   // Identify compatability class for VM's architecture and library's architecture
   // Obtain string descriptions for architectures
   arch_t lib_arch={elf_head.e_machine,0,elf_head.e_ident[EI_CLASS], elf_head.e_ident[EI_DATA], NULL};
   int running_arch_index=-1;
   for (unsigned int i=0 ; i < ARRAY_SIZE(arch_array) ; i++ ) {
     if (running_arch_code == arch_array[i].code) {
       running_arch_index    = i;
     }
     if (lib_arch.code == arch_array[i].code) {
       lib_arch.compat_class = arch_array[i].compat_class;
       lib_arch.name         = arch_array[i].name;
     }
   }
   assert(running_arch_index != -1,
     "Didn't find running architecture code (running_arch_code) in arch_array");
   if (running_arch_index == -1) {
     // Even though running architecture detection failed
     // we may still continue with reporting dlerror() message
     return NULL;
   }
   if (lib_arch.endianess != arch_array[running_arch_index].endianess) {
     ::snprintf(diag_msg_buf, diag_msg_max_length-1," (Possible cause: endianness mismatch)");
     return NULL;
   }
 #ifndef S390
   if (lib_arch.elf_class != arch_array[running_arch_index].elf_class) {
     ::snprintf(diag_msg_buf, diag_msg_max_length-1," (Possible cause: architecture word width mismatch)");
     return NULL;
   }
 #endif // !S390
   if (lib_arch.compat_class != arch_array[running_arch_index].compat_class) {
     if ( lib_arch.name!=NULL ) {
       ::snprintf(diag_msg_buf, diag_msg_max_length-1,
         " (Possible cause: can't load %s-bit .so on a %s-bit platform)",
         lib_arch.name, arch_array[running_arch_index].name);
     } else {
       ::snprintf(diag_msg_buf, diag_msg_max_length-1,
       " (Possible cause: can't load this .so (machine code=0x%x) on a %s-bit platform)",
         lib_arch.code,
         arch_array[running_arch_index].name);
     }
   }
   return NULL;
 }
 /*
  * glibc-2.0 libdl is not MT safe.  If you are building with any glibc,
  * chances are you might want to run the generated bits against glibc-2.0
  * libdl.so, so always use locking for any version of glibc.
  */
 void* os::dll_lookup(void* handle, const char* name) {
   pthread_mutex_lock(&dl_mutex);
   void* res = dlsym(handle, name);
   pthread_mutex_unlock(&dl_mutex);
   return res;
 }
 bool _print_ascii_file(const char* filename, outputStream* st) {
   int fd = open(filename, O_RDONLY);
   if (fd == -1) {
      return false;
   }
   char buf[32];
   int bytes;
   while ((bytes = read(fd, buf, sizeof(buf))) > 0) {
     st->print_raw(buf, bytes);
   }
   close(fd);
   return true;
 }
 void os::print_dll_info(outputStream *st) {
    st->print_cr("Dynamic libraries:");
    char fname[32];
    pid_t pid = os::Linux::gettid();
    jio_snprintf(fname, sizeof(fname), "/proc/%d/maps", pid);
    if (!_print_ascii_file(fname, st)) {
      st->print("Can not get library information for pid = %d\n", pid);
    }
 }
 void os::print_os_info(outputStream* st) {
   st->print("OS:");
   // Try to identify popular distros.
   // Most Linux distributions have /etc/XXX-release file, which contains
   // the OS version string. Some have more than one /etc/XXX-release file
   // (e.g. Mandrake has both /etc/mandrake-release and /etc/redhat-release.),
   // so the order is important.
   if (!_print_ascii_file("/etc/mandrake-release", st) &&
       !_print_ascii_file("/etc/sun-release", st) &&
       !_print_ascii_file("/etc/redhat-release", st) &&
       !_print_ascii_file("/etc/SuSE-release", st) &&
       !_print_ascii_file("/etc/turbolinux-release", st) &&
       !_print_ascii_file("/etc/gentoo-release", st) &&
       !_print_ascii_file("/etc/debian_version", st) &&
       !_print_ascii_file("/etc/ltib-release", st) &&
       !_print_ascii_file("/etc/angstrom-version", st)) {
       st->print("Linux");
   }
   st->cr();
   // kernel
   st->print("uname:");
   struct utsname name;
   uname(&name);
   st->print(name.sysname); st->print(" ");
   st->print(name.release); st->print(" ");
   st->print(name.version); st->print(" ");
   st->print(name.machine);
   st->cr();
   // Print warning if unsafe chroot environment detected
   if (unsafe_chroot_detected) {
     st->print("WARNING!! ");
     st->print_cr(unstable_chroot_error);
   }
   // libc, pthread
   st->print("libc:");
   st->print(os::Linux::glibc_version()); st->print(" ");
   st->print(os::Linux::libpthread_version()); st->print(" ");
   if (os::Linux::is_LinuxThreads()) {
      st->print("(%s stack)", os::Linux::is_floating_stack() ? "floating" : "fixed");
   }
   st->cr();
   // rlimit
   st->print("rlimit:");
   struct rlimit rlim;
   st->print(" STACK ");
   getrlimit(RLIMIT_STACK, &rlim);
   if (rlim.rlim_cur == RLIM_INFINITY) st->print("infinity");
   else st->print("%uk", rlim.rlim_cur >> 10);
   st->print(", CORE ");
   getrlimit(RLIMIT_CORE, &rlim);
   if (rlim.rlim_cur == RLIM_INFINITY) st->print("infinity");
   else st->print("%uk", rlim.rlim_cur >> 10);
   st->print(", NPROC ");
   getrlimit(RLIMIT_NPROC, &rlim);
   if (rlim.rlim_cur == RLIM_INFINITY) st->print("infinity");
   else st->print("%d", rlim.rlim_cur);
   st->print(", NOFILE ");
   getrlimit(RLIMIT_NOFILE, &rlim);
   if (rlim.rlim_cur == RLIM_INFINITY) st->print("infinity");
   else st->print("%d", rlim.rlim_cur);
   st->print(", AS ");
   getrlimit(RLIMIT_AS, &rlim);
   if (rlim.rlim_cur == RLIM_INFINITY) st->print("infinity");
   else st->print("%uk", rlim.rlim_cur >> 10);
   st->cr();
   // load average
   st->print("load average:");
   double loadavg[3];
   os::loadavg(loadavg, 3);
   st->print("%0.02f %0.02f %0.02f", loadavg[0], loadavg[1], loadavg[2]);
   st->cr();
   // meminfo
   st->print("\n/proc/meminfo:\n");
   _print_ascii_file("/proc/meminfo", st);
   st->cr();
 }
 void os::print_memory_info(outputStream* st) {
   st->print("Memory:");
   st->print(" %dk page", os::vm_page_size()>>10);
   // values in struct sysinfo are "unsigned long"
   struct sysinfo si;
   sysinfo(&si);
   st->print(", physical " UINT64_FORMAT "k",
             os::physical_memory() >> 10);
   st->print("(" UINT64_FORMAT "k free)",
             os::available_memory() >> 10);
   st->print(", swap " UINT64_FORMAT "k",
             ((jlong)si.totalswap * si.mem_unit) >> 10);
   st->print("(" UINT64_FORMAT "k free)",
             ((jlong)si.freeswap * si.mem_unit) >> 10);
   st->cr();
 }
 // Taken from /usr/include/bits/siginfo.h  Supposed to be architecture specific
 // but they're the same for all the linux arch that we support
 // and they're the same for solaris but there's no common place to put this.
 const char *ill_names[] = { "ILL0", "ILL_ILLOPC", "ILL_ILLOPN", "ILL_ILLADR",
                           "ILL_ILLTRP", "ILL_PRVOPC", "ILL_PRVREG",
                           "ILL_COPROC", "ILL_BADSTK" };
 const char *fpe_names[] = { "FPE0", "FPE_INTDIV", "FPE_INTOVF", "FPE_FLTDIV",
                           "FPE_FLTOVF", "FPE_FLTUND", "FPE_FLTRES",
                           "FPE_FLTINV", "FPE_FLTSUB", "FPE_FLTDEN" };
 const char *segv_names[] = { "SEGV0", "SEGV_MAPERR", "SEGV_ACCERR" };
 const char *bus_names[] = { "BUS0", "BUS_ADRALN", "BUS_ADRERR", "BUS_OBJERR" };
 void os::print_siginfo(outputStream* st, void* siginfo) {
   st->print("siginfo:");
   const int buflen = 100;
   char buf[buflen];
   siginfo_t *si = (siginfo_t*)siginfo;
   st->print("si_signo=%s: ", os::exception_name(si->si_signo, buf, buflen));
   if (si->si_errno != 0 && strerror_r(si->si_errno, buf, buflen) == 0) {
     st->print("si_errno=%s", buf);
   } else {
     st->print("si_errno=%d", si->si_errno);
   }
   const int c = si->si_code;
   assert(c > 0, "unexpected si_code");
   switch (si->si_signo) {
   case SIGILL:
     st->print(", si_code=%d (%s)", c, c > 8 ? "" : ill_names[c]);
     st->print(", si_addr=" PTR_FORMAT, si->si_addr);
     break;
   case SIGFPE:
     st->print(", si_code=%d (%s)", c, c > 9 ? "" : fpe_names[c]);
     st->print(", si_addr=" PTR_FORMAT, si->si_addr);
     break;
   case SIGSEGV:
     st->print(", si_code=%d (%s)", c, c > 2 ? "" : segv_names[c]);
     st->print(", si_addr=" PTR_FORMAT, si->si_addr);
     break;
   case SIGBUS:
     st->print(", si_code=%d (%s)", c, c > 3 ? "" : bus_names[c]);
     st->print(", si_addr=" PTR_FORMAT, si->si_addr);
     break;
   default:
     st->print(", si_code=%d", si->si_code);
     // no si_addr
   }
   if ((si->si_signo == SIGBUS || si->si_signo == SIGSEGV) &&
       UseSharedSpaces) {
     FileMapInfo* mapinfo = FileMapInfo::current_info();
     if (mapinfo->is_in_shared_space(si->si_addr)) {
       st->print("\n\nError accessing class data sharing archive."   \
                 " Mapped file inaccessible during execution, "      \
                 " possible disk/network problem.");
     }
   }
   st->cr();
 }
 static void print_signal_handler(outputStream* st, int sig,
                                  char* buf, size_t buflen);
 void os::print_signal_handlers(outputStream* st, char* buf, size_t buflen) {
   st->print_cr("Signal Handlers:");
   print_signal_handler(st, SIGSEGV, buf, buflen);
   print_signal_handler(st, SIGBUS , buf, buflen);
   print_signal_handler(st, SIGFPE , buf, buflen);
   print_signal_handler(st, SIGPIPE, buf, buflen);
   print_signal_handler(st, SIGXFSZ, buf, buflen);
   print_signal_handler(st, SIGILL , buf, buflen);
   print_signal_handler(st, INTERRUPT_SIGNAL, buf, buflen);
   print_signal_handler(st, SR_signum, buf, buflen);
   print_signal_handler(st, SHUTDOWN1_SIGNAL, buf, buflen);
   print_signal_handler(st, SHUTDOWN2_SIGNAL , buf, buflen);
   print_signal_handler(st, SHUTDOWN3_SIGNAL , buf, buflen);
   print_signal_handler(st, BREAK_SIGNAL, buf, buflen);
 }
 static char saved_jvm_path[MAXPATHLEN] = {0};
 // Find the full path to the current module, libjvm.so or libjvm_g.so
 void os::jvm_path(char *buf, jint buflen) {
   // Error checking.
   if (buflen < MAXPATHLEN) {
     assert(false, "must use a large-enough buffer");
     buf[0] = '\0';
     return;
   }
   // Lazy resolve the path to current module.
   if (saved_jvm_path[0] != 0) {
     strcpy(buf, saved_jvm_path);
     return;
   }
   char dli_fname[MAXPATHLEN];
   bool ret = dll_address_to_library_name(
                 CAST_FROM_FN_PTR(address, os::jvm_path),
                 dli_fname, sizeof(dli_fname), NULL);
   assert(ret != 0, "cannot locate libjvm");
   char *rp = realpath(dli_fname, buf);
   if (rp == NULL)
     return;
   if (strcmp(Arguments::sun_java_launcher(), "gamma") == 0) {
     // Support for the gamma launcher.  Typical value for buf is
     // "<JAVA_HOME>/jre/lib/<arch>/<vmtype>/libjvm.so".  If "/jre/lib/" appears at
     // the right place in the string, then assume we are installed in a JDK and
     // we're done.  Otherwise, check for a JAVA_HOME environment variable and fix
     // up the path so it looks like libjvm.so is installed there (append a
     // fake suffix hotspot/libjvm.so).
     const char *p = buf + strlen(buf) - 1;
     for (int count = 0; p > buf && count < 5; ++count) {
       for (--p; p > buf && *p != '/'; --p)
         /* empty */ ;
     }
     if (strncmp(p, "/jre/lib/", 9) != 0) {
       // Look for JAVA_HOME in the environment.
       char* java_home_var = ::getenv("JAVA_HOME");
       if (java_home_var != NULL && java_home_var[0] != 0) {
         char* jrelib_p;
         int len;
         // Check the current module name "libjvm.so" or "libjvm_g.so".
         p = strrchr(buf, '/');
         assert(strstr(p, "/libjvm") == p, "invalid library name");
         p = strstr(p, "_g") ? "_g" : "";
         rp = realpath(java_home_var, buf);
         if (rp == NULL)
           return;
         // determine if this is a legacy image or modules image
         // modules image doesn't have "jre" subdirectory
         len = strlen(buf);
         jrelib_p = buf + len;
         snprintf(jrelib_p, buflen-len, "/jre/lib/%s", cpu_arch);
         if (0 != access(buf, F_OK)) {
           snprintf(jrelib_p, buflen-len, "/lib/%s", cpu_arch);
         }
         if (0 == access(buf, F_OK)) {
           // Use current module name "libjvm[_g].so" instead of
           // "libjvm"debug_only("_g")".so" since for fastdebug version
           // we should have "libjvm.so" but debug_only("_g") adds "_g"!
           // It is used when we are choosing the HPI library's name
           // "libhpi[_g].so" in hpi::initialize_get_interface().
           len = strlen(buf);
           snprintf(buf + len, buflen-len, "/hotspot/libjvm%s.so", p);
         } else {
           // Go back to path of .so
           rp = realpath(dli_fname, buf);
           if (rp == NULL)
             return;
         }
       }
     }
   }
   strcpy(saved_jvm_path, buf);
 }
 void os::print_jni_name_prefix_on(outputStream* st, int args_size) {
   // no prefix required, not even "_"
 }
 void os::print_jni_name_suffix_on(outputStream* st, int args_size) {
   // no suffix required
 }
 ////////////////////////////////////////////////////////////////////////////////
 // sun.misc.Signal support
 static volatile jint sigint_count = 0;
 static void
 UserHandler(int sig, void *siginfo, void *context) {
   // 4511530 - sem_post is serialized and handled by the manager thread. When
   // the program is interrupted by Ctrl-C, SIGINT is sent to every thread. We
   // don't want to flood the manager thread with sem_post requests.
   if (sig == SIGINT && Atomic::add(1, &sigint_count) > 1)
       return;
   // Ctrl-C is pressed during error reporting, likely because the error
   // handler fails to abort. Let VM die immediately.
   if (sig == SIGINT && is_error_reported()) {
      os::die();
   }
   os::signal_notify(sig);
 }
 void* os::user_handler() {
   return CAST_FROM_FN_PTR(void*, UserHandler);
 }
 extern "C" {
   typedef void (*sa_handler_t)(int);
   typedef void (*sa_sigaction_t)(int, siginfo_t *, void *);
 }
 void* os::signal(int signal_number, void* handler) {
   struct sigaction sigAct, oldSigAct;
   sigfillset(&(sigAct.sa_mask));
   sigAct.sa_flags   = SA_RESTART|SA_SIGINFO;
   sigAct.sa_handler = CAST_TO_FN_PTR(sa_handler_t, handler);
   if (sigaction(signal_number, &sigAct, &oldSigAct)) {
     // -1 means registration failed
     return (void *)-1;
   }
   return CAST_FROM_FN_PTR(void*, oldSigAct.sa_handler);
 }
 void os::signal_raise(int signal_number) {
   ::raise(signal_number);
 }
 /*
  * The following code is moved from os.cpp for making this
  * code platform specific, which it is by its very nature.
  */
 // Will be modified when max signal is changed to be dynamic
 int os::sigexitnum_pd() {
   return NSIG;
 }
 // a counter for each possible signal value
 static volatile jint pending_signals[NSIG+1] = { 0 };
 // Linux(POSIX) specific hand shaking semaphore.
 static sem_t sig_sem;
 void os::signal_init_pd() {
   // Initialize signal structures
   ::memset((void*)pending_signals, 0, sizeof(pending_signals));
   // Initialize signal semaphore
   ::sem_init(&sig_sem, 0, 0);
 }
 void os::signal_notify(int sig) {
   Atomic::inc(&pending_signals[sig]);
   ::sem_post(&sig_sem);
 }
 static int check_pending_signals(bool wait) {
   Atomic::store(0, &sigint_count);
   for (;;) {
     for (int i = 0; i < NSIG + 1; i++) {
       jint n = pending_signals[i];
       if (n > 0 && n == Atomic::cmpxchg(n - 1, &pending_signals[i], n)) {
         return i;
       }
     }
     if (!wait) {
       return -1;
     }
     JavaThread *thread = JavaThread::current();
     ThreadBlockInVM tbivm(thread);
     bool threadIsSuspended;
     do {
       thread->set_suspend_equivalent();
       // cleared by handle_special_suspend_equivalent_condition() or java_suspend_self()
       ::sem_wait(&sig_sem);
       // were we externally suspended while we were waiting?
       threadIsSuspended = thread->handle_special_suspend_equivalent_condition();
       if (threadIsSuspended) {
         //
         // The semaphore has been incremented, but while we were waiting
         // another thread suspended us. We don't want to continue running
         // while suspended because that would surprise the thread that
         // suspended us.
         //
         ::sem_post(&sig_sem);
         thread->java_suspend_self();
       }
     } while (threadIsSuspended);
   }
 }
 int os::signal_lookup() {
   return check_pending_signals(false);
 }
 int os::signal_wait() {
   return check_pending_signals(true);
 }
 ////////////////////////////////////////////////////////////////////////////////
 // Virtual Memory
 int os::vm_page_size() {
   // Seems redundant as all get out
   assert(os::Linux::page_size() != -1, "must call os::init");
   return os::Linux::page_size();
 }
 // Solaris allocates memory by pages.
 int os::vm_allocation_granularity() {
   assert(os::Linux::page_size() != -1, "must call os::init");
   return os::Linux::page_size();
 }
 // Rationale behind this function:
 //  current (Mon Apr 25 20:12:18 MSD 2005) oprofile drops samples without executable
 //  mapping for address (see lookup_dcookie() in the kernel module), thus we cannot get
 //  samples for JITted code. Here we create private executable mapping over the code cache
 //  and then we can use standard (well, almost, as mapping can change) way to provide
 //  info for the reporting script by storing timestamp and location of symbol
 void linux_wrap_code(char* base, size_t size) {
   static volatile jint cnt = 0;
   if (!UseOprofile) {
     return;
   }
   char buf[PATH_MAX+1];
   int num = Atomic::add(1, &cnt);
   snprintf(buf, sizeof(buf), "%s/hs-vm-%d-%d",
            os::get_temp_directory(), os::current_process_id(), num);
   unlink(buf);
   int fd = open(buf, O_CREAT | O_RDWR, S_IRWXU);
   if (fd != -1) {
     off_t rv = lseek(fd, size-2, SEEK_SET);
     if (rv != (off_t)-1) {
       if (write(fd, "", 1) == 1) {
         mmap(base, size,
              PROT_READ|PROT_WRITE|PROT_EXEC,
              MAP_PRIVATE|MAP_FIXED|MAP_NORESERVE, fd, 0);
       }
     }
     close(fd);
     unlink(buf);
   }
 }
 // NOTE: Linux kernel does not really reserve the pages for us.
 //       All it does is to check if there are enough free pages
 //       left at the time of mmap(). This could be a potential
 //       problem.
 bool os::commit_memory(char* addr, size_t size, bool exec) {
   int prot = exec ? PROT_READ|PROT_WRITE|PROT_EXEC : PROT_READ|PROT_WRITE;
   uintptr_t res = (uintptr_t) ::mmap(addr, size, prot,
                                    MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0);
   return res != (uintptr_t) MAP_FAILED;
 }
 bool os::commit_memory(char* addr, size_t size, size_t alignment_hint,
                        bool exec) {
   return commit_memory(addr, size, exec);
 }
 void os::realign_memory(char *addr, size_t bytes, size_t alignment_hint) { }
 void os::free_memory(char *addr, size_t bytes) {
   ::mmap(addr, bytes, PROT_READ | PROT_WRITE,
          MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0);
 }
 void os::numa_make_global(char *addr, size_t bytes) {
   Linux::numa_interleave_memory(addr, bytes);
 }
 void os::numa_make_local(char *addr, size_t bytes, int lgrp_hint) {
   Linux::numa_tonode_memory(addr, bytes, lgrp_hint);
 }
 bool os::numa_topology_changed()   { return false; }
 size_t os::numa_get_groups_num() {
   int max_node = Linux::numa_max_node();
   return max_node > 0 ? max_node + 1 : 1;
 }
 int os::numa_get_group_id() {
   int cpu_id = Linux::sched_getcpu();
   if (cpu_id != -1) {
     int lgrp_id = Linux::get_node_by_cpu(cpu_id);
     if (lgrp_id != -1) {
       return lgrp_id;
     }
   }
   return 0;
 }
 size_t os::numa_get_leaf_groups(int *ids, size_t size) {
   for (size_t i = 0; i < size; i++) {
     ids[i] = i;
   }
   return size;
 }
 bool os::get_page_info(char *start, page_info* info) {
   return false;
 }
 char *os::scan_pages(char *start, char* end, page_info* page_expected, page_info* page_found) {
   return end;
 }
 extern "C" void numa_warn(int number, char *where, ...) { }
 extern "C" void numa_error(char *where) { }
 // If we are running with libnuma version > 2, then we should
 // be trying to use symbols with versions 1.1
 // If we are running with earlier version, which did not have symbol versions,
 // we should use the base version.
 void* os::Linux::libnuma_dlsym(void* handle, const char *name) {
   void *f = dlvsym(handle, name, "libnuma_1.1");
   if (f == NULL) {
     f = dlsym(handle, name);
   }
   return f;
 }
 bool os::Linux::libnuma_init() {
   // sched_getcpu() should be in libc.
   set_sched_getcpu(CAST_TO_FN_PTR(sched_getcpu_func_t,
                                   dlsym(RTLD_DEFAULT, "sched_getcpu")));
   if (sched_getcpu() != -1) { // Does it work?
     void *handle = dlopen("libnuma.so.1", RTLD_LAZY);
     if (handle != NULL) {
       set_numa_node_to_cpus(CAST_TO_FN_PTR(numa_node_to_cpus_func_t,
                                            libnuma_dlsym(handle, "numa_node_to_cpus")));
       set_numa_max_node(CAST_TO_FN_PTR(numa_max_node_func_t,
                                        libnuma_dlsym(handle, "numa_max_node")));
       set_numa_available(CAST_TO_FN_PTR(numa_available_func_t,
                                         libnuma_dlsym(handle, "numa_available")));
       set_numa_tonode_memory(CAST_TO_FN_PTR(numa_tonode_memory_func_t,
                                             libnuma_dlsym(handle, "numa_tonode_memory")));
       set_numa_interleave_memory(CAST_TO_FN_PTR(numa_interleave_memory_func_t,
                                             libnuma_dlsym(handle, "numa_interleave_memory")));
       if (numa_available() != -1) {
         set_numa_all_nodes((unsigned long*)libnuma_dlsym(handle, "numa_all_nodes"));
         // Create a cpu -> node mapping
         _cpu_to_node = new (ResourceObj::C_HEAP) GrowableArray<int>(0, true);
         rebuild_cpu_to_node_map();
         return true;
       }
     }
   }
   return false;
 }
 // rebuild_cpu_to_node_map() constructs a table mapping cpud id to node id.
 // The table is later used in get_node_by_cpu().
 void os::Linux::rebuild_cpu_to_node_map() {
   const size_t NCPUS = 32768; // Since the buffer size computation is very obscure
                               // in libnuma (possible values are starting from 16,
                               // and continuing up with every other power of 2, but less
                               // than the maximum number of CPUs supported by kernel), and
                               // is a subject to change (in libnuma version 2 the requirements
                               // are more reasonable) we'll just hardcode the number they use
                               // in the library.
   const size_t BitsPerCLong = sizeof(long) * CHAR_BIT;
   size_t cpu_num = os::active_processor_count();
   size_t cpu_map_size = NCPUS / BitsPerCLong;
   size_t cpu_map_valid_size =
     MIN2((cpu_num + BitsPerCLong - 1) / BitsPerCLong, cpu_map_size);
   cpu_to_node()->clear();
   cpu_to_node()->at_grow(cpu_num - 1);
   size_t node_num = numa_get_groups_num();
   unsigned long *cpu_map = NEW_C_HEAP_ARRAY(unsigned long, cpu_map_size);
   for (size_t i = 0; i < node_num; i++) {
     if (numa_node_to_cpus(i, cpu_map, cpu_map_size * sizeof(unsigned long)) != -1) {
       for (size_t j = 0; j < cpu_map_valid_size; j++) {
         if (cpu_map[j] != 0) {
           for (size_t k = 0; k < BitsPerCLong; k++) {
             if (cpu_map[j] & (1UL << k)) {
               cpu_to_node()->at_put(j * BitsPerCLong + k, i);
             }
           }
         }
       }
     }
   }
   FREE_C_HEAP_ARRAY(unsigned long, cpu_map);
 }
 int os::Linux::get_node_by_cpu(int cpu_id) {
   if (cpu_to_node() != NULL && cpu_id >= 0 && cpu_id < cpu_to_node()->length()) {
     return cpu_to_node()->at(cpu_id);
   }
   return -1;
 }
 GrowableArray<int>* os::Linux::_cpu_to_node;
 os::Linux::sched_getcpu_func_t os::Linux::_sched_getcpu;
 os::Linux::numa_node_to_cpus_func_t os::Linux::_numa_node_to_cpus;
 os::Linux::numa_max_node_func_t os::Linux::_numa_max_node;
 os::Linux::numa_available_func_t os::Linux::_numa_available;
 os::Linux::numa_tonode_memory_func_t os::Linux::_numa_tonode_memory;
 os::Linux::numa_interleave_memory_func_t os::Linux::_numa_interleave_memory;
 unsigned long* os::Linux::_numa_all_nodes;
 bool os::uncommit_memory(char* addr, size_t size) {
   uintptr_t res = (uintptr_t) ::mmap(addr, size, PROT_NONE,
                 MAP_PRIVATE|MAP_FIXED|MAP_NORESERVE|MAP_ANONYMOUS, -1, 0);
   return res  != (uintptr_t) MAP_FAILED;
 }
 // Linux uses a growable mapping for the stack, and if the mapping for
 // the stack guard pages is not removed when we detach a thread the
 // stack cannot grow beyond the pages where the stack guard was
 // mapped.  If at some point later in the process the stack expands to
 // that point, the Linux kernel cannot expand the stack any further
 // because the guard pages are in the way, and a segfault occurs.
 //
 // However, it's essential not to split the stack region by unmapping
 // a region (leaving a hole) that's already part of the stack mapping,
 // so if the stack mapping has already grown beyond the guard pages at
 // the time we create them, we have to truncate the stack mapping.
 // So, we need to know the extent of the stack mapping when
 // create_stack_guard_pages() is called.
 // Find the bounds of the stack mapping.  Return true for success.
 //
 // We only need this for stacks that are growable: at the time of
 // writing thread stacks don't use growable mappings (i.e. those
 // creeated with MAP_GROWSDOWN), and aren't marked "[stack]", so this
 // only applies to the main thread.
 static bool
 get_stack_bounds(uintptr_t *bottom, uintptr_t *top)
 {
   FILE *f = fopen("/proc/self/maps", "r");
   if (f == NULL)
     return false;
   while (!feof(f)) {
     size_t dummy;
     char *str = NULL;
     ssize_t len = getline(&str, &dummy, f);
     if (len == -1) {
       fclose(f);
       return false;
     }
     if (len > 0 && str[len-1] == '\n') {
       str[len-1] = 0;
       len--;
     }
     static const char *stack_str = "[stack]";
     if (len > (ssize_t)strlen(stack_str)
        && (strcmp(str + len - strlen(stack_str), stack_str) == 0)) {
       if (sscanf(str, "%" SCNxPTR "-%" SCNxPTR, bottom, top) == 2) {
         uintptr_t sp = (uintptr_t)__builtin_frame_address(0);
         if (sp >= *bottom && sp <= *top) {
           free(str);
           fclose(f);
           return true;
         }
       }
     }
     free(str);
   }
   fclose(f);
   return false;
 }
 // If the (growable) stack mapping already extends beyond the point
 // where we're going to put our guard pages, truncate the mapping at
 // that point by munmap()ping it.  This ensures that when we later
 // munmap() the guard pages we don't leave a hole in the stack
 // mapping. This only affects the main/initial thread, but guard
 // against future OS changes
 bool os::create_stack_guard_pages(char* addr, size_t size) {
   uintptr_t stack_extent, stack_base;
   bool chk_bounds = NOT_DEBUG(os::Linux::is_initial_thread()) DEBUG_ONLY(true);
   if (chk_bounds && get_stack_bounds(&stack_extent, &stack_base)) {
       assert(os::Linux::is_initial_thread(),
            "growable stack in non-initial thread");
     if (stack_extent < (uintptr_t)addr)
       ::munmap((void*)stack_extent, (uintptr_t)addr - stack_extent);
   }
   return os::commit_memory(addr, size);
 }
 // If this is a growable mapping, remove the guard pages entirely by
 // munmap()ping them.  If not, just call uncommit_memory(). This only
 // affects the main/initial thread, but guard against future OS changes
 bool os::remove_stack_guard_pages(char* addr, size_t size) {
   uintptr_t stack_extent, stack_base;
   bool chk_bounds = NOT_DEBUG(os::Linux::is_initial_thread()) DEBUG_ONLY(true);
   if (chk_bounds && get_stack_bounds(&stack_extent, &stack_base)) {
       assert(os::Linux::is_initial_thread(),
            "growable stack in non-initial thread");
     return ::munmap(addr, size) == 0;
   }
   return os::uncommit_memory(addr, size);
 }
 static address _highest_vm_reserved_address = NULL;
 // If 'fixed' is true, anon_mmap() will attempt to reserve anonymous memory
 // at 'requested_addr'. If there are existing memory mappings at the same
 // location, however, they will be overwritten. If 'fixed' is false,
 // 'requested_addr' is only treated as a hint, the return value may or
 // may not start from the requested address. Unlike Linux mmap(), this
 // function returns NULL to indicate failure.
 static char* anon_mmap(char* requested_addr, size_t bytes, bool fixed) {
   char * addr;
   int flags;
   flags = MAP_PRIVATE | MAP_NORESERVE | MAP_ANONYMOUS;
   if (fixed) {
     assert((uintptr_t)requested_addr % os::Linux::page_size() == 0, "unaligned address");
     flags |= MAP_FIXED;
   }
   // Map uncommitted pages PROT_READ and PROT_WRITE, change access
   // to PROT_EXEC if executable when we commit the page.
   addr = (char*)::mmap(requested_addr, bytes, PROT_READ|PROT_WRITE,
                        flags, -1, 0);
   if (addr != MAP_FAILED) {
     // anon_mmap() should only get called during VM initialization,
     // don't need lock (actually we can skip locking even it can be called
     // from multiple threads, because _highest_vm_reserved_address is just a
     // hint about the upper limit of non-stack memory regions.)
     if ((address)addr + bytes > _highest_vm_reserved_address) {
       _highest_vm_reserved_address = (address)addr + bytes;
     }
   }
   return addr == MAP_FAILED ? NULL : addr;
 }
 // Don't update _highest_vm_reserved_address, because there might be memory
 // regions above addr + size. If so, releasing a memory region only creates
 // a hole in the address space, it doesn't help prevent heap-stack collision.
 //
 static int anon_munmap(char * addr, size_t size) {
   return ::munmap(addr, size) == 0;
 }
 char* os::reserve_memory(size_t bytes, char* requested_addr,
                          size_t alignment_hint) {
   return anon_mmap(requested_addr, bytes, (requested_addr != NULL));
 }
 bool os::release_memory(char* addr, size_t size) {
   return anon_munmap(addr, size);
 }
 static address highest_vm_reserved_address() {
   return _highest_vm_reserved_address;
 }
 static bool linux_mprotect(char* addr, size_t size, int prot) {
   // Linux wants the mprotect address argument to be page aligned.
   char* bottom = (char*)align_size_down((intptr_t)addr, os::Linux::page_size());
   // According to SUSv3, mprotect() should only be used with mappings
   // established by mmap(), and mmap() always maps whole pages. Unaligned
   // 'addr' likely indicates problem in the VM (e.g. trying to change
   // protection of malloc'ed or statically allocated memory). Check the
   // caller if you hit this assert.
   assert(addr == bottom, "sanity check");
   size = align_size_up(pointer_delta(addr, bottom, 1) + size, os::Linux::page_size());
   return ::mprotect(bottom, size, prot) == 0;
 }
 // Set protections specified
 bool os::protect_memory(char* addr, size_t bytes, ProtType prot,
                         bool is_committed) {
   unsigned int p = 0;
   switch (prot) {
   case MEM_PROT_NONE: p = PROT_NONE; break;
   case MEM_PROT_READ: p = PROT_READ; break;
   case MEM_PROT_RW:   p = PROT_READ|PROT_WRITE; break;
   case MEM_PROT_RWX:  p = PROT_READ|PROT_WRITE|PROT_EXEC; break;
   default:
     ShouldNotReachHere();
   }
   // is_committed is unused.
   return linux_mprotect(addr, bytes, p);
 }
 bool os::guard_memory(char* addr, size_t size) {
   return linux_mprotect(addr, size, PROT_NONE);
 }
 bool os::unguard_memory(char* addr, size_t size) {
   return linux_mprotect(addr, size, PROT_READ|PROT_WRITE);
 }
 // Large page support
 static size_t _large_page_size = 0;
 bool os::large_page_init() {
   if (!UseLargePages) return false;
   if (LargePageSizeInBytes) {
     _large_page_size = LargePageSizeInBytes;
   } else {
     // large_page_size on Linux is used to round up heap size. x86 uses either
     // 2M or 4M page, depending on whether PAE (Physical Address Extensions)
     // mode is enabled. AMD64/EM64T uses 2M page in 64bit mode. IA64 can use
     // page as large as 256M.
     //
     // Here we try to figure out page size by parsing /proc/meminfo and looking
     // for a line with the following format:
     //    Hugepagesize:     2048 kB
     //
     // If we can't determine the value (e.g. /proc is not mounted, or the text
     // format has been changed), we'll use the largest page size supported by
     // the processor.
 #ifndef ZERO
     _large_page_size = IA32_ONLY(4 * M) AMD64_ONLY(2 * M) IA64_ONLY(256 * M) SPARC_ONLY(4 * M)
                        ARM_ONLY(2 * M) PPC_ONLY(4 * M);
 #endif // ZERO
     FILE *fp = fopen("/proc/meminfo", "r");
     if (fp) {
       while (!feof(fp)) {
         int x = 0;
         char buf[16];
         if (fscanf(fp, "Hugepagesize: %d", &x) == 1) {
           if (x && fgets(buf, sizeof(buf), fp) && strcmp(buf, " kB\n") == 0) {
             _large_page_size = x * K;
             break;
           }
         } else {
           // skip to next line
           for (;;) {
             int ch = fgetc(fp);
             if (ch == EOF || ch == (int)'\n') break;
           }
         }
       }
       fclose(fp);
     }
   }
   const size_t default_page_size = (size_t)Linux::page_size();
   if (_large_page_size > default_page_size) {
     _page_sizes[0] = _large_page_size;
     _page_sizes[1] = default_page_size;
     _page_sizes[2] = 0;
   }
   // Large page support is available on 2.6 or newer kernel, some vendors
   // (e.g. Redhat) have backported it to their 2.4 based distributions.
   // We optimistically assume the support is available. If later it turns out
   // not true, VM will automatically switch to use regular page size.
   return true;
 }
 #ifndef SHM_HUGETLB
 #define SHM_HUGETLB 04000
 #endif
 char* os::reserve_memory_special(size_t bytes, char* req_addr, bool exec) {
   // "exec" is passed in but not used.  Creating the shared image for
   // the code cache doesn't have an SHM_X executable permission to check.
   assert(UseLargePages, "only for large pages");
   key_t key = IPC_PRIVATE;
   char *addr;
   bool warn_on_failure = UseLargePages &&
                         (!FLAG_IS_DEFAULT(UseLargePages) ||
                          !FLAG_IS_DEFAULT(LargePageSizeInBytes)
                         );
   char msg[128];
   // Create a large shared memory region to attach to based on size.
   // Currently, size is the total size of the heap
   int shmid = shmget(key, bytes, SHM_HUGETLB|IPC_CREAT|SHM_R|SHM_W);
   if (shmid == -1) {
      // Possible reasons for shmget failure:
      // 1. shmmax is too small for Java heap.
      //    > check shmmax value: cat /proc/sys/kernel/shmmax
      //    > increase shmmax value: echo "0xffffffff" > /proc/sys/kernel/shmmax
      // 2. not enough large page memory.
      //    > check available large pages: cat /proc/meminfo
      //    > increase amount of large pages:
      //          echo new_value > /proc/sys/vm/nr_hugepages
      //      Note 1: different Linux may use different name for this property,
      //            e.g. on Redhat AS-3 it is "hugetlb_pool".
      //      Note 2: it's possible there's enough physical memory available but
      //            they are so fragmented after a long run that they can't
      //            coalesce into large pages. Try to reserve large pages when
      //            the system is still "fresh".
      if (warn_on_failure) {
        jio_snprintf(msg, sizeof(msg), "Failed to reserve shared memory (errno = %d).", errno);
        warning(msg);
      }
      return NULL;
   }
   // attach to the region
   addr = (char*)shmat(shmid, req_addr, 0);
   int err = errno;
   // Remove shmid. If shmat() is successful, the actual shared memory segment
   // will be deleted when it's detached by shmdt() or when the process
   // terminates. If shmat() is not successful this will remove the shared
   // segment immediately.
   shmctl(shmid, IPC_RMID, NULL);
   if ((intptr_t)addr == -1) {
      if (warn_on_failure) {
        jio_snprintf(msg, sizeof(msg), "Failed to attach shared memory (errno = %d).", err);
        warning(msg);
      }
      return NULL;
   }
   return addr;
 }
 bool os::release_memory_special(char* base, size_t bytes) {
   // detaching the SHM segment will also delete it, see reserve_memory_special()
   int rslt = shmdt(base);
   return rslt == 0;
 }
 size_t os::large_page_size() {
   return _large_page_size;
 }
 // Linux does not support anonymous mmap with large page memory. The only way
 // to reserve large page memory without file backing is through SysV shared
 // memory API. The entire memory region is committed and pinned upfront.
 // Hopefully this will change in the future...
 bool os::can_commit_large_page_memory() {
   return false;
 }
 bool os::can_execute_large_page_memory() {
   return false;
 }
 // Reserve memory at an arbitrary address, only if that area is
 // available (and not reserved for something else).
 char* os::attempt_reserve_memory_at(size_t bytes, char* requested_addr) {
   const int max_tries = 10;
   char* base[max_tries];
   size_t size[max_tries];
   const size_t gap = 0x000000;
   // Assert only that the size is a multiple of the page size, since
   // that's all that mmap requires, and since that's all we really know
   // about at this low abstraction level.  If we need higher alignment,
   // we can either pass an alignment to this method or verify alignment
   // in one of the methods further up the call chain.  See bug 5044738.
   assert(bytes % os::vm_page_size() == 0, "reserving unexpected size block");
   // Repeatedly allocate blocks until the block is allocated at the
   // right spot. Give up after max_tries. Note that reserve_memory() will
   // automatically update _highest_vm_reserved_address if the call is
   // successful. The variable tracks the highest memory address every reserved
   // by JVM. It is used to detect heap-stack collision if running with
   // fixed-stack LinuxThreads. Because here we may attempt to reserve more
   // space than needed, it could confuse the collision detecting code. To
   // solve the problem, save current _highest_vm_reserved_address and
   // calculate the correct value before return.
   address old_highest = _highest_vm_reserved_address;
   // Linux mmap allows caller to pass an address as hint; give it a try first,
   // if kernel honors the hint then we can return immediately.
   char * addr = anon_mmap(requested_addr, bytes, false);
   if (addr == requested_addr) {
      return requested_addr;
   }
   if (addr != NULL) {
      // mmap() is successful but it fails to reserve at the requested address
      anon_munmap(addr, bytes);
   }
   int i;
   for (i = 0; i < max_tries; ++i) {
     base[i] = reserve_memory(bytes);
     if (base[i] != NULL) {
       // Is this the block we wanted?
       if (base[i] == requested_addr) {
         size[i] = bytes;
         break;
       }
       // Does this overlap the block we wanted? Give back the overlapped
       // parts and try again.
       size_t top_overlap = requested_addr + (bytes + gap) - base[i];
       if (top_overlap >= 0 && top_overlap < bytes) {
         unmap_memory(base[i], top_overlap);
         base[i] += top_overlap;
         size[i] = bytes - top_overlap;
       } else {
         size_t bottom_overlap = base[i] + bytes - requested_addr;
         if (bottom_overlap >= 0 && bottom_overlap < bytes) {
           unmap_memory(requested_addr, bottom_overlap);
           size[i] = bytes - bottom_overlap;
         } else {
           size[i] = bytes;
         }
       }
     }
   }
   // Give back the unused reserved pieces.
   for (int j = 0; j < i; ++j) {
     if (base[j] != NULL) {
       unmap_memory(base[j], size[j]);
     }
   }
   if (i < max_tries) {
     _highest_vm_reserved_address = MAX2(old_highest, (address)requested_addr + bytes);
     return requested_addr;
   } else {
     _highest_vm_reserved_address = old_highest;
     return NULL;
   }
 }
 size_t os::read(int fd, void *buf, unsigned int nBytes) {
   return ::read(fd, buf, nBytes);
 }
 // TODO-FIXME: reconcile Solaris' os::sleep with the linux variation.
 // Solaris uses poll(), linux uses park().
 // Poll() is likely a better choice, assuming that Thread.interrupt()
 // generates a SIGUSRx signal. Note that SIGUSR1 can interfere with
 // SIGSEGV, see 4355769.
 const int NANOSECS_PER_MILLISECS = 1000000;
 int os::sleep(Thread* thread, jlong millis, bool interruptible) {
   assert(thread == Thread::current(),  "thread consistency check");
   ParkEvent * const slp = thread->_SleepEvent ;
   slp->reset() ;
   OrderAccess::fence() ;
   if (interruptible) {
     jlong prevtime = javaTimeNanos();
     for (;;) {
       if (os::is_interrupted(thread, true)) {
         return OS_INTRPT;
       }
       jlong newtime = javaTimeNanos();
       if (newtime - prevtime < 0) {
         // time moving backwards, should only happen if no monotonic clock
         // not a guarantee() because JVM should not abort on kernel/glibc bugs
         assert(!Linux::supports_monotonic_clock(), "time moving backwards");
       } else {
         millis -= (newtime - prevtime) / NANOSECS_PER_MILLISECS;
       }
       if(millis <= 0) {
         return OS_OK;
       }
       prevtime = newtime;
       {
         assert(thread->is_Java_thread(), "sanity check");
         JavaThread *jt = (JavaThread *) thread;
         ThreadBlockInVM tbivm(jt);
         OSThreadWaitState osts(jt->osthread(), false /* not Object.wait() */);
         jt->set_suspend_equivalent();
         // cleared by handle_special_suspend_equivalent_condition() or
         // java_suspend_self() via check_and_wait_while_suspended()
         slp->park(millis);
         // were we externally suspended while we were waiting?
         jt->check_and_wait_while_suspended();
       }
     }
   } else {
     OSThreadWaitState osts(thread->osthread(), false /* not Object.wait() */);
     jlong prevtime = javaTimeNanos();
     for (;;) {
       // It'd be nice to avoid the back-to-back javaTimeNanos() calls on
       // the 1st iteration ...
       jlong newtime = javaTimeNanos();
       if (newtime - prevtime < 0) {
         // time moving backwards, should only happen if no monotonic clock
         // not a guarantee() because JVM should not abort on kernel/glibc bugs
         assert(!Linux::supports_monotonic_clock(), "time moving backwards");
       } else {
         millis -= (newtime - prevtime) / NANOSECS_PER_MILLISECS;
       }
       if(millis <= 0) break ;
       prevtime = newtime;
       slp->park(millis);
     }
     return OS_OK ;
   }
 }
 int os::naked_sleep() {
   // %% make the sleep time an integer flag. for now use 1 millisec.
   return os::sleep(Thread::current(), 1, false);
 }
 // Sleep forever; naked call to OS-specific sleep; use with CAUTION
 void os::infinite_sleep() {
   while (true) {    // sleep forever ...
     ::sleep(100);   // ... 100 seconds at a time
   }
 }
 // Used to convert frequent JVM_Yield() to nops
 bool os::dont_yield() {
   return DontYieldALot;
 }
 void os::yield() {
   sched_yield();
 }
 os::YieldResult os::NakedYield() { sched_yield(); return os::YIELD_UNKNOWN ;}
 void os::yield_all(int attempts) {
   // Yields to all threads, including threads with lower priorities
   // Threads on Linux are all with same priority. The Solaris style
   // os::yield_all() with nanosleep(1ms) is not necessary.
   sched_yield();
 }
 // Called from the tight loops to possibly influence time-sharing heuristics
 void os::loop_breaker(int attempts) {
   os::yield_all(attempts);
 }
 ////////////////////////////////////////////////////////////////////////////////
 // thread priority support
 // Note: Normal Linux applications are run with SCHED_OTHER policy. SCHED_OTHER
 // only supports dynamic priority, static priority must be zero. For real-time
 // applications, Linux supports SCHED_RR which allows static priority (1-99).
 // However, for large multi-threaded applications, SCHED_RR is not only slower
 // than SCHED_OTHER, but also very unstable (my volano tests hang hard 4 out
 // of 5 runs - Sep 2005).
 //
 // The following code actually changes the niceness of kernel-thread/LWP. It
 // has an assumption that setpriority() only modifies one kernel-thread/LWP,
 // not the entire user process, and user level threads are 1:1 mapped to kernel
 // threads. It has always been the case, but could change in the future. For
 // this reason, the code should not be used as default (ThreadPriorityPolicy=0).
 // It is only used when ThreadPriorityPolicy=1 and requires root privilege.
 int os::java_to_os_priority[MaxPriority + 1] = {
 ,              // 0 Entry should never be used
 ,              // 1 MinPriority
 ,              // 2
 ,              // 3
 ,              // 4
 ,              // 5 NormPriority
   -1,              // 6
   -2,              // 7
   -3,              // 8
   -4,              // 9 NearMaxPriority
   -5               // 10 MaxPriority
 };
 static int prio_init() {
   if (ThreadPriorityPolicy == 1) {
     // Only root can raise thread priority. Don't allow ThreadPriorityPolicy=1
     // if effective uid is not root. Perhaps, a more elegant way of doing
     // this is to test CAP_SYS_NICE capability, but that will require libcap.so
     if (geteuid() != 0) {
       if (!FLAG_IS_DEFAULT(ThreadPriorityPolicy)) {
         warning("-XX:ThreadPriorityPolicy requires root privilege on Linux");
       }
       ThreadPriorityPolicy = 0;
     }
   }
   return 0;
 }
 OSReturn os::set_native_priority(Thread* thread, int newpri) {
   if ( !UseThreadPriorities || ThreadPriorityPolicy == 0 ) return OS_OK;
   int ret = setpriority(PRIO_PROCESS, thread->osthread()->thread_id(), newpri);
   return (ret == 0) ? OS_OK : OS_ERR;
 }
 OSReturn os::get_native_priority(const Thread* const thread, int *priority_ptr) {
   if ( !UseThreadPriorities || ThreadPriorityPolicy == 0 ) {
     *priority_ptr = java_to_os_priority[NormPriority];
     return OS_OK;
   }
   errno = 0;
   *priority_ptr = getpriority(PRIO_PROCESS, thread->osthread()->thread_id());
   return (*priority_ptr != -1 || errno == 0 ? OS_OK : OS_ERR);
 }
 // Hint to the underlying OS that a task switch would not be good.
 // Void return because it's a hint and can fail.
 void os::hint_no_preempt() {}
 ////////////////////////////////////////////////////////////////////////////////
 // suspend/resume support
 //  the low-level signal-based suspend/resume support is a remnant from the
 //  old VM-suspension that used to be for java-suspension, safepoints etc,
 //  within hotspot. Now there is a single use-case for this:
 //    - calling get_thread_pc() on the VMThread by the flat-profiler task
 //      that runs in the watcher thread.
 //  The remaining code is greatly simplified from the more general suspension
 //  code that used to be used.
 //
 //  The protocol is quite simple:
 //  - suspend:
 //      - sends a signal to the target thread
 //      - polls the suspend state of the osthread using a yield loop
 //      - target thread signal handler (SR_handler) sets suspend state
 //        and blocks in sigsuspend until continued
 //  - resume:
 //      - sets target osthread state to continue
 //      - sends signal to end the sigsuspend loop in the SR_handler
 //
 //  Note that the SR_lock plays no role in this suspend/resume protocol.
 //
 static void resume_clear_context(OSThread *osthread) {
   osthread->set_ucontext(NULL);
   osthread->set_siginfo(NULL);
   // notify the suspend action is completed, we have now resumed
   osthread->sr.clear_suspended();
 }
 static void suspend_save_context(OSThread *osthread, siginfo_t* siginfo, ucontext_t* context) {
   osthread->set_ucontext(context);
   osthread->set_siginfo(siginfo);
 }
 //
 // Handler function invoked when a thread's execution is suspended or
 // resumed. We have to be careful that only async-safe functions are
 // called here (Note: most pthread functions are not async safe and
 // should be avoided.)
 //
 // Note: sigwait() is a more natural fit than sigsuspend() from an
 // interface point of view, but sigwait() prevents the signal hander
 // from being run. libpthread would get very confused by not having
 // its signal handlers run and prevents sigwait()'s use with the
 // mutex granting granting signal.
 //
 // Currently only ever called on the VMThread
 //
 static void SR_handler(int sig, siginfo_t* siginfo, ucontext_t* context) {
   // Save and restore errno to avoid confusing native code with EINTR
   // after sigsuspend.
   int old_errno = errno;
   Thread* thread = Thread::current();
   OSThread* osthread = thread->osthread();
   assert(thread->is_VM_thread(), "Must be VMThread");
   // read current suspend action
   int action = osthread->sr.suspend_action();
   if (action == SR_SUSPEND) {
     suspend_save_context(osthread, siginfo, context);
     // Notify the suspend action is about to be completed. do_suspend()
     // waits until SR_SUSPENDED is set and then returns. We will wait
     // here for a resume signal and that completes the suspend-other
     // action. do_suspend/do_resume is always called as a pair from
     // the same thread - so there are no races
     // notify the caller
     osthread->sr.set_suspended();
     sigset_t suspend_set;  // signals for sigsuspend()
     // get current set of blocked signals and unblock resume signal
     pthread_sigmask(SIG_BLOCK, NULL, &suspend_set);
     sigdelset(&suspend_set, SR_signum);
     // wait here until we are resumed
     do {
       sigsuspend(&suspend_set);
       // ignore all returns until we get a resume signal
     } while (osthread->sr.suspend_action() != SR_CONTINUE);
     resume_clear_context(osthread);
   } else {
     assert(action == SR_CONTINUE, "unexpected sr action");
     // nothing special to do - just leave the handler
   }
   errno = old_errno;
 }
 static int SR_initialize() {
   struct sigaction act;
   char *s;
   /* Get signal number to use for suspend/resume */
   if ((s = ::getenv("_JAVA_SR_SIGNUM")) != 0) {
     int sig = ::strtol(s, 0, 10);
     if (sig > 0 || sig < _NSIG) {
         SR_signum = sig;
     }
   }
   assert(SR_signum > SIGSEGV && SR_signum > SIGBUS,
         "SR_signum must be greater than max(SIGSEGV, SIGBUS), see 4355769");
   sigemptyset(&SR_sigset);
   sigaddset(&SR_sigset, SR_signum);
   /* Set up signal handler for suspend/resume */
   act.sa_flags = SA_RESTART|SA_SIGINFO;
   act.sa_handler = (void (*)(int)) SR_handler;
   // SR_signum is blocked by default.
   // 4528190 - We also need to block pthread restart signal (32 on all
   // supported Linux platforms). Note that LinuxThreads need to block
   // this signal for all threads to work properly. So we don't have
   // to use hard-coded signal number when setting up the mask.
   pthread_sigmask(SIG_BLOCK, NULL, &act.sa_mask);
   if (sigaction(SR_signum, &act, 0) == -1) {
     return -1;
   }
   // Save signal flag
   os::Linux::set_our_sigflags(SR_signum, act.sa_flags);
   return 0;
 }
 static int SR_finalize() {
   return 0;
 }
 // returns true on success and false on error - really an error is fatal
 // but this seems the normal response to library errors
 static bool do_suspend(OSThread* osthread) {
   // mark as suspended and send signal
   osthread->sr.set_suspend_action(SR_SUSPEND);
   int status = pthread_kill(osthread->pthread_id(), SR_signum);
   assert_status(status == 0, status, "pthread_kill");
   // check status and wait until notified of suspension
   if (status == 0) {
     for (int i = 0; !osthread->sr.is_suspended(); i++) {
       os::yield_all(i);
     }
     osthread->sr.set_suspend_action(SR_NONE);
     return true;
   }
   else {
     osthread->sr.set_suspend_action(SR_NONE);
     return false;
   }
 }
 static void do_resume(OSThread* osthread) {
   assert(osthread->sr.is_suspended(), "thread should be suspended");
   osthread->sr.set_suspend_action(SR_CONTINUE);
   int status = pthread_kill(osthread->pthread_id(), SR_signum);
   assert_status(status == 0, status, "pthread_kill");
   // check status and wait unit notified of resumption
   if (status == 0) {
     for (int i = 0; osthread->sr.is_suspended(); i++) {
       os::yield_all(i);
     }
   }
   osthread->sr.set_suspend_action(SR_NONE);
 }
 ////////////////////////////////////////////////////////////////////////////////
 // interrupt support
 void os::interrupt(Thread* thread) {
   assert(Thread::current() == thread || Threads_lock->owned_by_self(),
     "possibility of dangling Thread pointer");
   OSThread* osthread = thread->osthread();
   if (!osthread->interrupted()) {
     osthread->set_interrupted(true);
     // More than one thread can get here with the same value of osthread,
     // resulting in multiple notifications.  We do, however, want the store
     // to interrupted() to be visible to other threads before we execute unpark().
     OrderAccess::fence();
     ParkEvent * const slp = thread->_SleepEvent ;
     if (slp != NULL) slp->unpark() ;
   }
   // For JSR166. Unpark even if interrupt status already was set
   if (thread->is_Java_thread())
     ((JavaThread*)thread)->parker()->unpark();
   ParkEvent * ev = thread->_ParkEvent ;
   if (ev != NULL) ev->unpark() ;
 }
 bool os::is_interrupted(Thread* thread, bool clear_interrupted) {
   assert(Thread::current() == thread || Threads_lock->owned_by_self(),
     "possibility of dangling Thread pointer");
   OSThread* osthread = thread->osthread();
   bool interrupted = osthread->interrupted();
   if (interrupted && clear_interrupted) {
     osthread->set_interrupted(false);
     // consider thread->_SleepEvent->reset() ... optional optimization
   }
   return interrupted;
 }
 ///////////////////////////////////////////////////////////////////////////////////
 // signal handling (except suspend/resume)
 // This routine may be used by user applications as a "hook" to catch signals.
 // The user-defined signal handler must pass unrecognized signals to this
 // routine, and if it returns true (non-zero), then the signal handler must
 // return immediately.  If the flag "abort_if_unrecognized" is true, then this
 // routine will never retun false (zero), but instead will execute a VM panic
 // routine kill the process.
 //
 // If this routine returns false, it is OK to call it again.  This allows
 // the user-defined signal handler to perform checks either before or after
 // the VM performs its own checks.  Naturally, the user code would be making
 // a serious error if it tried to handle an exception (such as a null check
 // or breakpoint) that the VM was generating for its own correct operation.
 //
 // This routine may recognize any of the following kinds of signals:
 //    SIGBUS, SIGSEGV, SIGILL, SIGFPE, SIGQUIT, SIGPIPE, SIGXFSZ, SIGUSR1.
 // It should be consulted by handlers for any of those signals.
 //
 // The caller of this routine must pass in the three arguments supplied
 // to the function referred to in the "sa_sigaction" (not the "sa_handler")
 // field of the structure passed to sigaction().  This routine assumes that
 // the sa_flags field passed to sigaction() includes SA_SIGINFO and SA_RESTART.
 //
 // Note that the VM will print warnings if it detects conflicting signal
 // handlers, unless invoked with the option "-XX:+AllowUserSignalHandlers".
 //
 extern "C" int
 JVM_handle_linux_signal(int signo, siginfo_t* siginfo,
                         void* ucontext, int abort_if_unrecognized);
 void signalHandler(int sig, siginfo_t* info, void* uc) {
   assert(info != NULL && uc != NULL, "it must be old kernel");
   JVM_handle_linux_signal(sig, info, uc, true);
 }
 // This boolean allows users to forward their own non-matching signals
 // to JVM_handle_linux_signal, harmlessly.
 bool os::Linux::signal_handlers_are_installed = false;
 // For signal-chaining
 struct sigaction os::Linux::sigact[MAXSIGNUM];
 unsigned int os::Linux::sigs = 0;
 bool os::Linux::libjsig_is_loaded = false;
 typedef struct sigaction *(*get_signal_t)(int);
 get_signal_t os::Linux::get_signal_action = NULL;
 struct sigaction* os::Linux::get_chained_signal_action(int sig) {
   struct sigaction *actp = NULL;
   if (libjsig_is_loaded) {
     // Retrieve the old signal handler from libjsig
     actp = (*get_signal_action)(sig);
   }
   if (actp == NULL) {
     // Retrieve the preinstalled signal handler from jvm
     actp = get_preinstalled_handler(sig);
   }
   return actp;
 }
 static bool call_chained_handler(struct sigaction *actp, int sig,
                                  siginfo_t *siginfo, void *context) {
   // Call the old signal handler
   if (actp->sa_handler == SIG_DFL) {
     // It's more reasonable to let jvm treat it as an unexpected exception
     // instead of taking the default action.
     return false;
   } else if (actp->sa_handler != SIG_IGN) {
     if ((actp->sa_flags & SA_NODEFER) == 0) {
       // automaticlly block the signal
       sigaddset(&(actp->sa_mask), sig);
     }
     sa_handler_t hand;
     sa_sigaction_t sa;
     bool siginfo_flag_set = (actp->sa_flags & SA_SIGINFO) != 0;
     // retrieve the chained handler
     if (siginfo_flag_set) {
       sa = actp->sa_sigaction;
     } else {
       hand = actp->sa_handler;
     }
     if ((actp->sa_flags & SA_RESETHAND) != 0) {
       actp->sa_handler = SIG_DFL;
     }
     // try to honor the signal mask
     sigset_t oset;
     pthread_sigmask(SIG_SETMASK, &(actp->sa_mask), &oset);
     // call into the chained handler
     if (siginfo_flag_set) {
       (*sa)(sig, siginfo, context);
     } else {
       (*hand)(sig);
     }
     // restore the signal mask
     pthread_sigmask(SIG_SETMASK, &oset, 0);
   }
   // Tell jvm's signal handler the signal is taken care of.
   return true;
 }
 bool os::Linux::chained_handler(int sig, siginfo_t* siginfo, void* context) {
   bool chained = false;
   // signal-chaining
   if (UseSignalChaining) {
     struct sigaction *actp = get_chained_signal_action(sig);
     if (actp != NULL) {
       chained = call_chained_handler(actp, sig, siginfo, context);
     }
   }
   return chained;
 }
 struct sigaction* os::Linux::get_preinstalled_handler(int sig) {
   if ((( (unsigned int)1 << sig ) & sigs) != 0) {
     return &sigact[sig];
   }
   return NULL;
 }
 void os::Linux::save_preinstalled_handler(int sig, struct sigaction& oldAct) {
   assert(sig > 0 && sig < MAXSIGNUM, "vm signal out of expected range");
   sigact[sig] = oldAct;
   sigs |= (unsigned int)1 << sig;
 }
 // for diagnostic
 int os::Linux::sigflags[MAXSIGNUM];
 int os::Linux::get_our_sigflags(int sig) {
   assert(sig > 0 && sig < MAXSIGNUM, "vm signal out of expected range");
   return sigflags[sig];
 }
 void os::Linux::set_our_sigflags(int sig, int flags) {
   assert(sig > 0 && sig < MAXSIGNUM, "vm signal out of expected range");
   sigflags[sig] = flags;
 }
 void os::Linux::set_signal_handler(int sig, bool set_installed) {
   // Check for overwrite.
   struct sigaction oldAct;
   sigaction(sig, (struct sigaction*)NULL, &oldAct);
   void* oldhand = oldAct.sa_sigaction
                 ? CAST_FROM_FN_PTR(void*,  oldAct.sa_sigaction)
                 : CAST_FROM_FN_PTR(void*,  oldAct.sa_handler);
   if (oldhand != CAST_FROM_FN_PTR(void*, SIG_DFL) &&
       oldhand != CAST_FROM_FN_PTR(void*, SIG_IGN) &&
       oldhand != CAST_FROM_FN_PTR(void*, (sa_sigaction_t)signalHandler)) {
     if (AllowUserSignalHandlers || !set_installed) {
       // Do not overwrite; user takes responsibility to forward to us.
       return;
     } else if (UseSignalChaining) {
       // save the old handler in jvm
       save_preinstalled_handler(sig, oldAct);
       // libjsig also interposes the sigaction() call below and saves the
       // old sigaction on it own.
     } else {
       fatal(err_msg("Encountered unexpected pre-existing sigaction handler "
                     "%#lx for signal %d.", (long)oldhand, sig));
     }
   }
   struct sigaction sigAct;
   sigfillset(&(sigAct.sa_mask));
   sigAct.sa_handler = SIG_DFL;
   if (!set_installed) {
     sigAct.sa_flags = SA_SIGINFO|SA_RESTART;
   } else {
     sigAct.sa_sigaction = signalHandler;
     sigAct.sa_flags = SA_SIGINFO|SA_RESTART;
   }
   // Save flags, which are set by ours
   assert(sig > 0 && sig < MAXSIGNUM, "vm signal out of expected range");
   sigflags[sig] = sigAct.sa_flags;
   int ret = sigaction(sig, &sigAct, &oldAct);
   assert(ret == 0, "check");
   void* oldhand2  = oldAct.sa_sigaction
                   ? CAST_FROM_FN_PTR(void*, oldAct.sa_sigaction)
                   : CAST_FROM_FN_PTR(void*, oldAct.sa_handler);
   assert(oldhand2 == oldhand, "no concurrent signal handler installation");
 }
 // install signal handlers for signals that HotSpot needs to
 // handle in order to support Java-level exception handling.
 void os::Linux::install_signal_handlers() {
   if (!signal_handlers_are_installed) {
     signal_handlers_are_installed = true;
     // signal-chaining
     typedef void (*signal_setting_t)();
     signal_setting_t begin_signal_setting = NULL;
     signal_setting_t end_signal_setting = NULL;
     begin_signal_setting = CAST_TO_FN_PTR(signal_setting_t,
                              dlsym(RTLD_DEFAULT, "JVM_begin_signal_setting"));
     if (begin_signal_setting != NULL) {
       end_signal_setting = CAST_TO_FN_PTR(signal_setting_t,
                              dlsym(RTLD_DEFAULT, "JVM_end_signal_setting"));
       get_signal_action = CAST_TO_FN_PTR(get_signal_t,
                             dlsym(RTLD_DEFAULT, "JVM_get_signal_action"));
       libjsig_is_loaded = true;
       assert(UseSignalChaining, "should enable signal-chaining");
     }
     if (libjsig_is_loaded) {
       // Tell libjsig jvm is setting signal handlers
       (*begin_signal_setting)();
     }
     set_signal_handler(SIGSEGV, true);
     set_signal_handler(SIGPIPE, true);
     set_signal_handler(SIGBUS, true);
     set_signal_handler(SIGILL, true);
     set_signal_handler(SIGFPE, true);
     set_signal_handler(SIGXFSZ, true);
     if (libjsig_is_loaded) {
       // Tell libjsig jvm finishes setting signal handlers
       (*end_signal_setting)();
     }
     // We don't activate signal checker if libjsig is in place, we trust ourselves
     // and if UserSignalHandler is installed all bets are off
     if (CheckJNICalls) {
       if (libjsig_is_loaded) {
         tty->print_cr("Info: libjsig is activated, all active signal checking is disabled");
         check_signals = false;
       }
       if (AllowUserSignalHandlers) {
         tty->print_cr("Info: AllowUserSignalHandlers is activated, all active signal checking is disabled");
         check_signals = false;
       }
     }
   }
 }
 // This is the fastest way to get thread cpu time on Linux.
 // Returns cpu time (user+sys) for any thread, not only for current.
 // POSIX compliant clocks are implemented in the kernels 2.6.16+.
 // It might work on 2.6.10+ with a special kernel/glibc patch.
 // For reference, please, see IEEE Std 1003.1-2004:
 //   http://www.unix.org/single_unix_specification
 jlong os::Linux::fast_thread_cpu_time(clockid_t clockid) {
   struct timespec tp;
   int rc = os::Linux::clock_gettime(clockid, &tp);
   assert(rc == 0, "clock_gettime is expected to return 0 code");
   return (tp.tv_sec * SEC_IN_NANOSECS) + tp.tv_nsec;
 }
 /////
 // glibc on Linux platform uses non-documented flag
 // to indicate, that some special sort of signal
 // trampoline is used.
 // We will never set this flag, and we should
 // ignore this flag in our diagnostic
 #ifdef SIGNIFICANT_SIGNAL_MASK
 #undef SIGNIFICANT_SIGNAL_MASK
 #endif
 #define SIGNIFICANT_SIGNAL_MASK (~0x04000000)
 static const char* get_signal_handler_name(address handler,
                                            char* buf, int buflen) {
   int offset;
   bool found = os::dll_address_to_library_name(handler, buf, buflen, &offset);
   if (found) {
     // skip directory names
     const char *p1, *p2;
     p1 = buf;
     size_t len = strlen(os::file_separator());
     while ((p2 = strstr(p1, os::file_separator())) != NULL) p1 = p2 + len;
     jio_snprintf(buf, buflen, "%s+0x%x", p1, offset);
   } else {
     jio_snprintf(buf, buflen, PTR_FORMAT, handler);
   }
   return buf;
 }
 static void print_signal_handler(outputStream* st, int sig,
                                  char* buf, size_t buflen) {
   struct sigaction sa;
   sigaction(sig, NULL, &sa);
   // See comment for SIGNIFICANT_SIGNAL_MASK define
   sa.sa_flags &= SIGNIFICANT_SIGNAL_MASK;
   st->print("%s: ", os::exception_name(sig, buf, buflen));
   address handler = (sa.sa_flags & SA_SIGINFO)
     ? CAST_FROM_FN_PTR(address, sa.sa_sigaction)
     : CAST_FROM_FN_PTR(address, sa.sa_handler);
   if (handler == CAST_FROM_FN_PTR(address, SIG_DFL)) {
     st->print("SIG_DFL");
   } else if (handler == CAST_FROM_FN_PTR(address, SIG_IGN)) {
     st->print("SIG_IGN");
   } else {
     st->print("[%s]", get_signal_handler_name(handler, buf, buflen));
   }
   st->print(", sa_mask[0]=" PTR32_FORMAT, *(uint32_t*)&sa.sa_mask);
   address rh = VMError::get_resetted_sighandler(sig);
   // May be, handler was resetted by VMError?
   if(rh != NULL) {
     handler = rh;
     sa.sa_flags = VMError::get_resetted_sigflags(sig) & SIGNIFICANT_SIGNAL_MASK;
   }
   st->print(", sa_flags="   PTR32_FORMAT, sa.sa_flags);
   // Check: is it our handler?
   if(handler == CAST_FROM_FN_PTR(address, (sa_sigaction_t)signalHandler) ||
      handler == CAST_FROM_FN_PTR(address, (sa_sigaction_t)SR_handler)) {
     // It is our signal handler
     // check for flags, reset system-used one!
     if((int)sa.sa_flags != os::Linux::get_our_sigflags(sig)) {
       st->print(
                 ", flags was changed from " PTR32_FORMAT ", consider using jsig library",
                 os::Linux::get_our_sigflags(sig));
     }
   }
   st->cr();
 }
 #define DO_SIGNAL_CHECK(sig) \
   if (!sigismember(&check_signal_done, sig)) \
     os::Linux::check_signal_handler(sig)
 // This method is a periodic task to check for misbehaving JNI applications
 // under CheckJNI, we can add any periodic checks here
 void os::run_periodic_checks() {
   if (check_signals == false) return;
   // SEGV and BUS if overridden could potentially prevent
   // generation of hs*.log in the event of a crash, debugging
   // such a case can be very challenging, so we absolutely
   // check the following for a good measure:
   DO_SIGNAL_CHECK(SIGSEGV);
   DO_SIGNAL_CHECK(SIGILL);
   DO_SIGNAL_CHECK(SIGFPE);
   DO_SIGNAL_CHECK(SIGBUS);
   DO_SIGNAL_CHECK(SIGPIPE);
   DO_SIGNAL_CHECK(SIGXFSZ);
   // ReduceSignalUsage allows the user to override these handlers
   // see comments at the very top and jvm_solaris.h
   if (!ReduceSignalUsage) {
     DO_SIGNAL_CHECK(SHUTDOWN1_SIGNAL);
     DO_SIGNAL_CHECK(SHUTDOWN2_SIGNAL);
     DO_SIGNAL_CHECK(SHUTDOWN3_SIGNAL);
     DO_SIGNAL_CHECK(BREAK_SIGNAL);
   }
   DO_SIGNAL_CHECK(SR_signum);
   DO_SIGNAL_CHECK(INTERRUPT_SIGNAL);
 }
 typedef int (*os_sigaction_t)(int, const struct sigaction *, struct sigaction *);
 static os_sigaction_t os_sigaction = NULL;
 void os::Linux::check_signal_handler(int sig) {
   char buf[O_BUFLEN];
   address jvmHandler = NULL;
   struct sigaction act;
   if (os_sigaction == NULL) {
     // only trust the default sigaction, in case it has been interposed
     os_sigaction = (os_sigaction_t)dlsym(RTLD_DEFAULT, "sigaction");
     if (os_sigaction == NULL) return;
   }
   os_sigaction(sig, (struct sigaction*)NULL, &act);
   act.sa_flags &= SIGNIFICANT_SIGNAL_MASK;
   address thisHandler = (act.sa_flags & SA_SIGINFO)
     ? CAST_FROM_FN_PTR(address, act.sa_sigaction)
     : CAST_FROM_FN_PTR(address, act.sa_handler) ;
   switch(sig) {
   case SIGSEGV:
   case SIGBUS:
   case SIGFPE:
   case SIGPIPE:
   case SIGILL:
   case SIGXFSZ:
     jvmHandler = CAST_FROM_FN_PTR(address, (sa_sigaction_t)signalHandler);
     break;
   case SHUTDOWN1_SIGNAL:
   case SHUTDOWN2_SIGNAL:
   case SHUTDOWN3_SIGNAL:
   case BREAK_SIGNAL:
     jvmHandler = (address)user_handler();
     break;
   case INTERRUPT_SIGNAL:
     jvmHandler = CAST_FROM_FN_PTR(address, SIG_DFL);
     break;
   default:
     if (sig == SR_signum) {
       jvmHandler = CAST_FROM_FN_PTR(address, (sa_sigaction_t)SR_handler);
     } else {
       return;
     }
     break;
   }
   if (thisHandler != jvmHandler) {
     tty->print("Warning: %s handler ", exception_name(sig, buf, O_BUFLEN));
     tty->print("expected:%s", get_signal_handler_name(jvmHandler, buf, O_BUFLEN));
     tty->print_cr("  found:%s", get_signal_handler_name(thisHandler, buf, O_BUFLEN));
     // No need to check this sig any longer
     sigaddset(&check_signal_done, sig);
   } else if(os::Linux::get_our_sigflags(sig) != 0 && (int)act.sa_flags != os::Linux::get_our_sigflags(sig)) {
     tty->print("Warning: %s handler flags ", exception_name(sig, buf, O_BUFLEN));
     tty->print("expected:" PTR32_FORMAT, os::Linux::get_our_sigflags(sig));
     tty->print_cr("  found:" PTR32_FORMAT, act.sa_flags);
     // No need to check this sig any longer
     sigaddset(&check_signal_done, sig);
   }
   // Dump all the signal
   if (sigismember(&check_signal_done, sig)) {
     print_signal_handlers(tty, buf, O_BUFLEN);
   }
 }
 extern void report_error(char* file_name, int line_no, char* title, char* format, ...);
 extern bool signal_name(int signo, char* buf, size_t len);
 const char* os::exception_name(int exception_code, char* buf, size_t size) {
   if (0 < exception_code && exception_code <= SIGRTMAX) {
     // signal
     if (!signal_name(exception_code, buf, size)) {
       jio_snprintf(buf, size, "SIG%d", exception_code);
     }
     return buf;
   } else {
     return NULL;
   }
 }
 // this is called _before_ the most of global arguments have been parsed
 void os::init(void) {
   char dummy;   /* used to get a guess on initial stack address */
 //  first_hrtime = gethrtime();
   // With LinuxThreads the JavaMain thread pid (primordial thread)
   // is different than the pid of the java launcher thread.
   // So, on Linux, the launcher thread pid is passed to the VM
   // via the sun.java.launcher.pid property.
   // Use this property instead of getpid() if it was correctly passed.
   // See bug 6351349.
   pid_t java_launcher_pid = (pid_t) Arguments::sun_java_launcher_pid();
   _initial_pid = (java_launcher_pid > 0) ? java_launcher_pid : getpid();
   clock_tics_per_sec = sysconf(_SC_CLK_TCK);
   init_random(1234567);
   ThreadCritical::initialize();
   Linux::set_page_size(sysconf(_SC_PAGESIZE));
   if (Linux::page_size() == -1) {
     fatal(err_msg("os_linux.cpp: os::init: sysconf failed (%s)",
                   strerror(errno)));
   }
   init_page_sizes((size_t) Linux::page_size());
   Linux::initialize_system_info();
   // main_thread points to the aboriginal thread
   Linux::_main_thread = pthread_self();
   Linux::clock_init();
   initial_time_count = os::elapsed_counter();
   pthread_mutex_init(&dl_mutex, NULL);
 }
 // To install functions for atexit system call
 extern "C" {
   static void perfMemory_exit_helper() {
     perfMemory_exit();
   }
 }
 // this is called _after_ the global arguments have been parsed
 jint os::init_2(void)
 {
   Linux::fast_thread_clock_init();
   // Allocate a single page and mark it as readable for safepoint polling
   address polling_page = (address) ::mmap(NULL, Linux::page_size(), PROT_READ, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
   guarantee( polling_page != MAP_FAILED, "os::init_2: failed to allocate polling page" );
   os::set_polling_page( polling_page );
 #ifndef PRODUCT
   if(Verbose && PrintMiscellaneous)
     tty->print("[SafePoint Polling address: " INTPTR_FORMAT "]\n", (intptr_t)polling_page);
 #endif
   if (!UseMembar) {
     address mem_serialize_page = (address) ::mmap(NULL, Linux::page_size(), PROT_READ | PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
     guarantee( mem_serialize_page != NULL, "mmap Failed for memory serialize page");
     os::set_memory_serialize_page( mem_serialize_page );
 #ifndef PRODUCT
     if(Verbose && PrintMiscellaneous)
       tty->print("[Memory Serialize  Page address: " INTPTR_FORMAT "]\n", (intptr_t)mem_serialize_page);
 #endif
   }
   FLAG_SET_DEFAULT(UseLargePages, os::large_page_init());
   // initialize suspend/resume support - must do this before signal_sets_init()
   if (SR_initialize() != 0) {
     perror("SR_initialize failed");
     return JNI_ERR;
   }
   Linux::signal_sets_init();
   Linux::install_signal_handlers();
   size_t threadStackSizeInBytes = ThreadStackSize * K;
   if (threadStackSizeInBytes != 0 &&
       threadStackSizeInBytes < Linux::min_stack_allowed) {
         tty->print_cr("\nThe stack size specified is too small, "
                       "Specify at least %dk",
                       Linux::min_stack_allowed / K);
         return JNI_ERR;
   }
   // Make the stack size a multiple of the page size so that
   // the yellow/red zones can be guarded.
   JavaThread::set_stack_size_at_create(round_to(threadStackSizeInBytes,
         vm_page_size()));
   Linux::capture_initial_stack(JavaThread::stack_size_at_create());
   Linux::libpthread_init();
   if (PrintMiscellaneous && (Verbose || WizardMode)) {
      tty->print_cr("[HotSpot is running with %s, %s(%s)]\n",
           Linux::glibc_version(), Linux::libpthread_version(),
           Linux::is_floating_stack() ? "floating stack" : "fixed stack");
   }
   if (UseNUMA) {
     if (!Linux::libnuma_init()) {
       UseNUMA = false;
     } else {
       if ((Linux::numa_max_node() < 1)) {
         // There's only one node(they start from 0), disable NUMA.
         UseNUMA = false;
       }
     }
     if (!UseNUMA && ForceNUMA) {
       UseNUMA = true;
     }
   }
   if (MaxFDLimit) {
     // set the number of file descriptors to max. print out error
     // if getrlimit/setrlimit fails but continue regardless.
     struct rlimit nbr_files;
     int status = getrlimit(RLIMIT_NOFILE, &nbr_files);
     if (status != 0) {
       if (PrintMiscellaneous && (Verbose || WizardMode))
         perror("os::init_2 getrlimit failed");
     } else {
       nbr_files.rlim_cur = nbr_files.rlim_max;
       status = setrlimit(RLIMIT_NOFILE, &nbr_files);
       if (status != 0) {
         if (PrintMiscellaneous && (Verbose || WizardMode))
           perror("os::init_2 setrlimit failed");
       }
     }
   }
   // Initialize lock used to serialize thread creation (see os::create_thread)
   Linux::set_createThread_lock(new Mutex(Mutex::leaf, "createThread_lock", false));
   // Initialize HPI.
   jint hpi_result = hpi::initialize();
   if (hpi_result != JNI_OK) {
     tty->print_cr("There was an error trying to initialize the HPI library.");
     return hpi_result;
   }
   // at-exit methods are called in the reverse order of their registration.
   // atexit functions are called on return from main or as a result of a
   // call to exit(3C). There can be only 32 of these functions registered
   // and atexit() does not set errno.
   if (PerfAllowAtExitRegistration) {
     // only register atexit functions if PerfAllowAtExitRegistration is set.
     // atexit functions can be delayed until process exit time, which
     // can be problematic for embedded VM situations. Embedded VMs should
     // call DestroyJavaVM() to assure that VM resources are released.
     // note: perfMemory_exit_helper atexit function may be removed in
     // the future if the appropriate cleanup code can be added to the
     // VM_Exit VMOperation's doit method.
     if (atexit(perfMemory_exit_helper) != 0) {
       warning("os::init2 atexit(perfMemory_exit_helper) failed");
     }
   }
   // initialize thread priority policy
   prio_init();
   return JNI_OK;
 }
 // this is called at the end of vm_initialization
 void os::init_3(void) { }
 // Mark the polling page as unreadable
 void os::make_polling_page_unreadable(void) {
   if( !guard_memory((char*)_polling_page, Linux::page_size()) )
     fatal("Could not disable polling page");
 };
 // Mark the polling page as readable
 void os::make_polling_page_readable(void) {
   if( !linux_mprotect((char *)_polling_page, Linux::page_size(), PROT_READ)) {
     fatal("Could not enable polling page");
   }
 };
 int os::active_processor_count() {
   // Linux doesn't yet have a (official) notion of processor sets,
   // so just return the number of online processors.
   int online_cpus = ::sysconf(_SC_NPROCESSORS_ONLN);
   assert(online_cpus > 0 && online_cpus <= processor_count(), "sanity check");
   return online_cpus;
 }
 bool os::distribute_processes(uint length, uint* distribution) {
   // Not yet implemented.
   return false;
 }
 bool os::bind_to_processor(uint processor_id) {
   // Not yet implemented.
   return false;
 }
 ///
 // Suspends the target using the signal mechanism and then grabs the PC before
 // resuming the target. Used by the flat-profiler only
 ExtendedPC os::get_thread_pc(Thread* thread) {
   // Make sure that it is called by the watcher for the VMThread
   assert(Thread::current()->is_Watcher_thread(), "Must be watcher");
   assert(thread->is_VM_thread(), "Can only be called for VMThread");
   ExtendedPC epc;
   OSThread* osthread = thread->osthread();
   if (do_suspend(osthread)) {
     if (osthread->ucontext() != NULL) {
       epc = os::Linux::ucontext_get_pc(osthread->ucontext());
     } else {
       // NULL context is unexpected, double-check this is the VMThread
       guarantee(thread->is_VM_thread(), "can only be called for VMThread");
     }
     do_resume(osthread);
   }
   // failure means pthread_kill failed for some reason - arguably this is
   // a fatal problem, but such problems are ignored elsewhere
   return epc;
 }
 int os::Linux::safe_cond_timedwait(pthread_cond_t *_cond, pthread_mutex_t *_mutex, const struct timespec *_abstime)
 {
    if (is_NPTL()) {
       return pthread_cond_timedwait(_cond, _mutex, _abstime);
    } else {
 #ifndef IA64
       // 6292965: LinuxThreads pthread_cond_timedwait() resets FPU control
       // word back to default 64bit precision if condvar is signaled. Java
       // wants 53bit precision.  Save and restore current value.
       int fpu = get_fpu_control_word();
 #endif // IA64
       int status = pthread_cond_timedwait(_cond, _mutex, _abstime);
 #ifndef IA64
       set_fpu_control_word(fpu);
 #endif // IA64
       return status;
    }
 }
 ////////////////////////////////////////////////////////////////////////////////
 // debug support
 static address same_page(address x, address y) {
   int page_bits = -os::vm_page_size();
   if ((intptr_t(x) & page_bits) == (intptr_t(y) & page_bits))
     return x;
   else if (x > y)
     return (address)(intptr_t(y) | ~page_bits) + 1;
   else
     return (address)(intptr_t(y) & page_bits);
 }
 bool os::find(address addr, outputStream* st) {
   Dl_info dlinfo;
   memset(&dlinfo, 0, sizeof(dlinfo));
   if (dladdr(addr, &dlinfo)) {
     st->print(PTR_FORMAT ": ", addr);
     if (dlinfo.dli_sname != NULL) {
       st->print("%s+%#x", dlinfo.dli_sname,
                  addr - (intptr_t)dlinfo.dli_saddr);
     } else if (dlinfo.dli_fname) {
       st->print("<offset %#x>", addr - (intptr_t)dlinfo.dli_fbase);
     } else {
       st->print("<absolute address>");
     }
     if (dlinfo.dli_fname) {
       st->print(" in %s", dlinfo.dli_fname);
     }
     if (dlinfo.dli_fbase) {
       st->print(" at " PTR_FORMAT, dlinfo.dli_fbase);
     }
     st->cr();
     if (Verbose) {
       // decode some bytes around the PC
       address begin = same_page(addr-40, addr);
       address end   = same_page(addr+40, addr);
       address       lowest = (address) dlinfo.dli_sname;
       if (!lowest)  lowest = (address) dlinfo.dli_fbase;
       if (begin < lowest)  begin = lowest;
       Dl_info dlinfo2;
       if (dladdr(end, &dlinfo2) && dlinfo2.dli_saddr != dlinfo.dli_saddr
           && end > dlinfo2.dli_saddr && dlinfo2.dli_saddr > begin)
         end = (address) dlinfo2.dli_saddr;
       Disassembler::decode(begin, end, st);
     }
     return true;
   }
   return false;
 }
 ////////////////////////////////////////////////////////////////////////////////
 // misc
 // This does not do anything on Linux. This is basically a hook for being
 // able to use structured exception handling (thread-local exception filters)
 // on, e.g., Win32.
 void
 os::os_exception_wrapper(java_call_t f, JavaValue* value, methodHandle* method,
                          JavaCallArguments* args, Thread* thread) {
   f(value, method, args, thread);
 }
 void os::print_statistics() {
 }
 int os::message_box(const char* title, const char* message) {
   int i;
   fdStream err(defaultStream::error_fd());
   for (i = 0; i < 78; i++) err.print_raw("=");
   err.cr();
   err.print_raw_cr(title);
   for (i = 0; i < 78; i++) err.print_raw("-");
   err.cr();
   err.print_raw_cr(message);
   for (i = 0; i < 78; i++) err.print_raw("=");
   err.cr();
   char buf[16];
   // Prevent process from exiting upon "read error" without consuming all CPU
   while (::read(0, buf, sizeof(buf)) <= 0) { ::sleep(100); }
   return buf[0] == 'y' || buf[0] == 'Y';
 }
 int os::stat(const char *path, struct stat *sbuf) {
   char pathbuf[MAX_PATH];
   if (strlen(path) > MAX_PATH - 1) {
     errno = ENAMETOOLONG;
     return -1;
   }
   hpi::native_path(strcpy(pathbuf, path));
   return ::stat(pathbuf, sbuf);
 }
 bool os::check_heap(bool force) {
   return true;
 }
 int local_vsnprintf(char* buf, size_t count, const char* format, va_list args) {
   return ::vsnprintf(buf, count, format, args);
 }
 // Is a (classpath) directory empty?
 bool os::dir_is_empty(const char* path) {
   DIR *dir = NULL;
   struct dirent *ptr;
   dir = opendir(path);
   if (dir == NULL) return true;
   /* Scan the directory */
   bool result = true;
   char buf[sizeof(struct dirent) + MAX_PATH];
   while (result && (ptr = ::readdir(dir)) != NULL) {
     if (strcmp(ptr->d_name, ".") != 0 && strcmp(ptr->d_name, "..") != 0) {
       result = false;
     }
   }
   closedir(dir);
   return result;
 }
 // create binary file, rewriting existing file if required
 int os::create_binary_file(const char* path, bool rewrite_existing) {
   int oflags = O_WRONLY | O_CREAT;
   if (!rewrite_existing) {
     oflags |= O_EXCL;
   }
   return ::open64(path, oflags, S_IREAD | S_IWRITE);
 }
 // return current position of file pointer
 jlong os::current_file_offset(int fd) {
   return (jlong)::lseek64(fd, (off64_t)0, SEEK_CUR);
 }
 // move file pointer to the specified offset
 jlong os::seek_to_file_offset(int fd, jlong offset) {
   return (jlong)::lseek64(fd, (off64_t)offset, SEEK_SET);
 }
 // Map a block of memory.
 char* os::map_memory(int fd, const char* file_name, size_t file_offset,
                      char *addr, size_t bytes, bool read_only,
                      bool allow_exec) {
   int prot;
   int flags;
   if (read_only) {
     prot = PROT_READ;
     flags = MAP_SHARED;
   } else {
     prot = PROT_READ | PROT_WRITE;
     flags = MAP_PRIVATE;
   }
   if (allow_exec) {
     prot |= PROT_EXEC;
   }
   if (addr != NULL) {
     flags |= MAP_FIXED;
   }
   char* mapped_address = (char*)mmap(addr, (size_t)bytes, prot, flags,
                                      fd, file_offset);
   if (mapped_address == MAP_FAILED) {
     return NULL;
   }
   return mapped_address;
 }
 // Remap a block of memory.
 char* os::remap_memory(int fd, const char* file_name, size_t file_offset,
                        char *addr, size_t bytes, bool read_only,
                        bool allow_exec) {
   // same as map_memory() on this OS
   return os::map_memory(fd, file_name, file_offset, addr, bytes, read_only,
                         allow_exec);
 }
 // Unmap a block of memory.
 bool os::unmap_memory(char* addr, size_t bytes) {
   return munmap(addr, bytes) == 0;
 }
 static jlong slow_thread_cpu_time(Thread *thread, bool user_sys_cpu_time);
 static clockid_t thread_cpu_clockid(Thread* thread) {
   pthread_t tid = thread->osthread()->pthread_id();
   clockid_t clockid;
   // Get thread clockid
   int rc = os::Linux::pthread_getcpuclockid(tid, &clockid);
   assert(rc == 0, "pthread_getcpuclockid is expected to return 0 code");
   return clockid;
 }
 // current_thread_cpu_time(bool) and thread_cpu_time(Thread*, bool)
 // are used by JVM M&M and JVMTI to get user+sys or user CPU time
 // of a thread.
 //
 // current_thread_cpu_time() and thread_cpu_time(Thread*) returns
 // the fast estimate available on the platform.
 jlong os::current_thread_cpu_time() {
   if (os::Linux::supports_fast_thread_cpu_time()) {
     return os::Linux::fast_thread_cpu_time(CLOCK_THREAD_CPUTIME_ID);
   } else {
     // return user + sys since the cost is the same
     return slow_thread_cpu_time(Thread::current(), true /* user + sys */);
   }
 }
 jlong os::thread_cpu_time(Thread* thread) {
   // consistent with what current_thread_cpu_time() returns
   if (os::Linux::supports_fast_thread_cpu_time()) {
     return os::Linux::fast_thread_cpu_time(thread_cpu_clockid(thread));
   } else {
     return slow_thread_cpu_time(thread, true /* user + sys */);
   }
 }
 jlong os::current_thread_cpu_time(bool user_sys_cpu_time) {
   if (user_sys_cpu_time && os::Linux::supports_fast_thread_cpu_time()) {
     return os::Linux::fast_thread_cpu_time(CLOCK_THREAD_CPUTIME_ID);
   } else {
     return slow_thread_cpu_time(Thread::current(), user_sys_cpu_time);
   }
 }
 jlong os::thread_cpu_time(Thread *thread, bool user_sys_cpu_time) {
   if (user_sys_cpu_time && os::Linux::supports_fast_thread_cpu_time()) {
     return os::Linux::fast_thread_cpu_time(thread_cpu_clockid(thread));
   } else {
     return slow_thread_cpu_time(thread, user_sys_cpu_time);
   }
 }
 //
 //  -1 on error.
 //
 static jlong slow_thread_cpu_time(Thread *thread, bool user_sys_cpu_time) {
   static bool proc_pid_cpu_avail = true;
   static bool proc_task_unchecked = true;
   static const char *proc_stat_path = "/proc/%d/stat";
   pid_t  tid = thread->osthread()->thread_id();
   int i;
   char *s;
   char stat[2048];
   int statlen;
   char proc_name[64];
   int count;
   long sys_time, user_time;
   char string[64];
   char cdummy;
   int idummy;
   long ldummy;
   FILE *fp;
   // We first try accessing /proc/<pid>/cpu since this is faster to
   // process.  If this file is not present (linux kernels 2.5 and above)
   // then we open /proc/<pid>/stat.
   if ( proc_pid_cpu_avail ) {
     sprintf(proc_name, "/proc/%d/cpu", tid);
     fp =  fopen(proc_name, "r");
     if ( fp != NULL ) {
       count = fscanf( fp, "%s %lu %lu\n", string, &user_time, &sys_time);
       fclose(fp);
       if ( count != 3 ) return -1;
       if (user_sys_cpu_time) {
         return ((jlong)sys_time + (jlong)user_time) * (1000000000 / clock_tics_per_sec);
       } else {
         return (jlong)user_time * (1000000000 / clock_tics_per_sec);
       }
     }
     else proc_pid_cpu_avail = false;
   }
   // The /proc/<tid>/stat aggregates per-process usage on
   // new Linux kernels 2.6+ where NPTL is supported.
   // The /proc/self/task/<tid>/stat still has the per-thread usage.
   // See bug 6328462.
   // There can be no directory /proc/self/task on kernels 2.4 with NPTL
   // and possibly in some other cases, so we check its availability.
   if (proc_task_unchecked && os::Linux::is_NPTL()) {
     // This is executed only once
     proc_task_unchecked = false;
     fp = fopen("/proc/self/task", "r");
     if (fp != NULL) {
       proc_stat_path = "/proc/self/task/%d/stat";
       fclose(fp);
     }
   }
   sprintf(proc_name, proc_stat_path, tid);
   fp = fopen(proc_name, "r");
   if ( fp == NULL ) return -1;
   statlen = fread(stat, 1, 2047, fp);
   stat[statlen] = '\0';
   fclose(fp);
   // Skip pid and the command string. Note that we could be dealing with
   // weird command names, e.g. user could decide to rename java launcher
   // to "java 1.4.2 :)", then the stat file would look like
   //                1234 (java 1.4.2 :)) R ... ...
   // We don't really need to know the command string, just find the last
   // occurrence of ")" and then start parsing from there. See bug 4726580.
   s = strrchr(stat, ')');
   i = 0;
   if (s == NULL ) return -1;
   // Skip blank chars
   do s++; while (isspace(*s));
   count = sscanf(s,"%c %d %d %d %d %d %lu %lu %lu %lu %lu %lu %lu",
                  &cdummy, &idummy, &idummy, &idummy, &idummy, &idummy,
                  &ldummy, &ldummy, &ldummy, &ldummy, &ldummy,
                  &user_time, &sys_time);
   if ( count != 13 ) return -1;
   if (user_sys_cpu_time) {
     return ((jlong)sys_time + (jlong)user_time) * (1000000000 / clock_tics_per_sec);
   } else {
     return (jlong)user_time * (1000000000 / clock_tics_per_sec);
   }
 }
 void os::current_thread_cpu_time_info(jvmtiTimerInfo *info_ptr) {
   info_ptr->max_value = ALL_64_BITS;       // will not wrap in less than 64 bits
   info_ptr->may_skip_backward = false;     // elapsed time not wall time
   info_ptr->may_skip_forward = false;      // elapsed time not wall time
   info_ptr->kind = JVMTI_TIMER_TOTAL_CPU;  // user+system time is returned
 }
 void os::thread_cpu_time_info(jvmtiTimerInfo *info_ptr) {
   info_ptr->max_value = ALL_64_BITS;       // will not wrap in less than 64 bits
   info_ptr->may_skip_backward = false;     // elapsed time not wall time
   info_ptr->may_skip_forward = false;      // elapsed time not wall time
   info_ptr->kind = JVMTI_TIMER_TOTAL_CPU;  // user+system time is returned
 }
 bool os::is_thread_cpu_time_supported() {
   return true;
 }
 // System loadavg support.  Returns -1 if load average cannot be obtained.
 // Linux doesn't yet have a (official) notion of processor sets,
 // so just return the system wide load average.
 int os::loadavg(double loadavg[], int nelem) {
   return ::getloadavg(loadavg, nelem);
 }
 void os::pause() {
   char filename[MAX_PATH];
   if (PauseAtStartupFile && PauseAtStartupFile[0]) {
     jio_snprintf(filename, MAX_PATH, PauseAtStartupFile);
   } else {
     jio_snprintf(filename, MAX_PATH, "./vm.paused.%d", current_process_id());
   }
   int fd = ::open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0666);
   if (fd != -1) {
     struct stat buf;
     close(fd);
     while (::stat(filename, &buf) == 0) {
       (void)::poll(NULL, 0, 100);
     }
   } else {
     jio_fprintf(stderr,
       "Could not open pause file '%s', continuing immediately.\n", filename);
   }
 }
 extern "C" {
 /**
  * NOTE: the following code is to keep the green threads code
  * in the libjava.so happy. Once the green threads is removed,
  * these code will no longer be needed.
  */
 int
 jdk_waitpid(pid_t pid, int* status, int options) {
     return waitpid(pid, status, options);
 }
 int
 fork1() {
     return fork();
 }
 int
 jdk_sem_init(sem_t *sem, int pshared, unsigned int value) {
     return sem_init(sem, pshared, value);
 }
 int
 jdk_sem_post(sem_t *sem) {
     return sem_post(sem);
 }
 int
 jdk_sem_wait(sem_t *sem) {
     return sem_wait(sem);
 }
 int
 jdk_pthread_sigmask(int how , const sigset_t* newmask, sigset_t* oldmask) {
     return pthread_sigmask(how , newmask, oldmask);
 }
 }
 // Refer to the comments in os_solaris.cpp park-unpark.
 //
 // Beware -- Some versions of NPTL embody a flaw where pthread_cond_timedwait() can
 // hang indefinitely.  For instance NPTL 0.60 on 2.4.21-4ELsmp is vulnerable.
 // For specifics regarding the bug see GLIBC BUGID 261237 :
 //    http://www.mail-archive.com/debian-glibc@lists.debian.org/msg10837.html.
 // Briefly, pthread_cond_timedwait() calls with an expiry time that's not in the future
 // will either hang or corrupt the condvar, resulting in subsequent hangs if the condvar
 // is used.  (The simple C test-case provided in the GLIBC bug report manifests the
 // hang).  The JVM is vulernable via sleep(), Object.wait(timo), LockSupport.parkNanos()
 // and monitorenter when we're using 1-0 locking.  All those operations may result in
 // calls to pthread_cond_timedwait().  Using LD_ASSUME_KERNEL to use an older version
 // of libpthread avoids the problem, but isn't practical.
 //
 // Possible remedies:
 //
 // 1.   Establish a minimum relative wait time.  50 to 100 msecs seems to work.
 //      This is palliative and probabilistic, however.  If the thread is preempted
 //      between the call to compute_abstime() and pthread_cond_timedwait(), more
 //      than the minimum period may have passed, and the abstime may be stale (in the
 //      past) resultin in a hang.   Using this technique reduces the odds of a hang
 //      but the JVM is still vulnerable, particularly on heavily loaded systems.
 //
 // 2.   Modify park-unpark to use per-thread (per ParkEvent) pipe-pairs instead
 //      of the usual flag-condvar-mutex idiom.  The write side of the pipe is set
 //      NDELAY. unpark() reduces to write(), park() reduces to read() and park(timo)
 //      reduces to poll()+read().  This works well, but consumes 2 FDs per extant
 //      thread.
 //
 // 3.   Embargo pthread_cond_timedwait() and implement a native "chron" thread
 //      that manages timeouts.  We'd emulate pthread_cond_timedwait() by enqueuing
 //      a timeout request to the chron thread and then blocking via pthread_cond_wait().
 //      This also works well.  In fact it avoids kernel-level scalability impediments
 //      on certain platforms that don't handle lots of active pthread_cond_timedwait()
 //      timers in a graceful fashion.
 //
 // 4.   When the abstime value is in the past it appears that control returns
 //      correctly from pthread_cond_timedwait(), but the condvar is left corrupt.
 //      Subsequent timedwait/wait calls may hang indefinitely.  Given that, we
 //      can avoid the problem by reinitializing the condvar -- by cond_destroy()
 //      followed by cond_init() -- after all calls to pthread_cond_timedwait().
 //      It may be possible to avoid reinitialization by checking the return
 //      value from pthread_cond_timedwait().  In addition to reinitializing the
 //      condvar we must establish the invariant that cond_signal() is only called
 //      within critical sections protected by the adjunct mutex.  This prevents
 //      cond_signal() from "seeing" a condvar that's in the midst of being
 //      reinitialized or that is corrupt.  Sadly, this invariant obviates the
 //      desirable signal-after-unlock optimization that avoids futile context switching.
 //
 //      I'm also concerned that some versions of NTPL might allocate an auxilliary
 //      structure when a condvar is used or initialized.  cond_destroy()  would
 //      release the helper structure.  Our reinitialize-after-timedwait fix
 //      put excessive stress on malloc/free and locks protecting the c-heap.
 //
 // We currently use (4).  See the WorkAroundNTPLTimedWaitHang flag.
 // It may be possible to refine (4) by checking the kernel and NTPL verisons
 // and only enabling the work-around for vulnerable environments.
 // utility to compute the abstime argument to timedwait:
 // millis is the relative timeout time
 // abstime will be the absolute timeout time
 // TODO: replace compute_abstime() with unpackTime()
 static struct timespec* compute_abstime(timespec* abstime, jlong millis) {
   if (millis < 0)  millis = 0;
   struct timeval now;
   int status = gettimeofday(&now, NULL);
   assert(status == 0, "gettimeofday");
   jlong seconds = millis / 1000;
   millis %= 1000;
   if (seconds > 50000000) { // see man cond_timedwait(3T)
     seconds = 50000000;
   }
   abstime->tv_sec = now.tv_sec  + seconds;
   long       usec = now.tv_usec + millis * 1000;
   if (usec >= 1000000) {
     abstime->tv_sec += 1;
     usec -= 1000000;
   }
   abstime->tv_nsec = usec * 1000;
   return abstime;
 }
 // Test-and-clear _Event, always leaves _Event set to 0, returns immediately.
 // Conceptually TryPark() should be equivalent to park(0).
 int os::PlatformEvent::TryPark() {
   for (;;) {
     const int v = _Event ;
     guarantee ((v == 0) || (v == 1), "invariant") ;
     if (Atomic::cmpxchg (0, &_Event, v) == v) return v  ;
   }
 }
 void os::PlatformEvent::park() {       // AKA "down()"
   // Invariant: Only the thread associated with the Event/PlatformEvent
   // may call park().
   // TODO: assert that _Assoc != NULL or _Assoc == Self
   int v ;
   for (;;) {
       v = _Event ;
       if (Atomic::cmpxchg (v-1, &_Event, v) == v) break ;
   }
   guarantee (v >= 0, "invariant") ;
   if (v == 0) {
      // Do this the hard way by blocking ...
      int status = pthread_mutex_lock(_mutex);
      assert_status(status == 0, status, "mutex_lock");
      guarantee (_nParked == 0, "invariant") ;
      ++ _nParked ;
      while (_Event < 0) {
         status = pthread_cond_wait(_cond, _mutex);
         // for some reason, under 2.7 lwp_cond_wait() may return ETIME ...
         // Treat this the same as if the wait was interrupted
         if (status == ETIME) { status = EINTR; }
         assert_status(status == 0 || status == EINTR, status, "cond_wait");
      }
      -- _nParked ;
     // In theory we could move the ST of 0 into _Event past the unlock(),
     // but then we'd need a MEMBAR after the ST.
     _Event = 0 ;
      status = pthread_mutex_unlock(_mutex);
      assert_status(status == 0, status, "mutex_unlock");
   }
   guarantee (_Event >= 0, "invariant") ;
 }
 int os::PlatformEvent::park(jlong millis) {
   guarantee (_nParked == 0, "invariant") ;
   int v ;
   for (;;) {
       v = _Event ;
       if (Atomic::cmpxchg (v-1, &_Event, v) == v) break ;
   }
   guarantee (v >= 0, "invariant") ;
   if (v != 0) return OS_OK ;
   // We do this the hard way, by blocking the thread.
   // Consider enforcing a minimum timeout value.
   struct timespec abst;
   compute_abstime(&abst, millis);
   int ret = OS_TIMEOUT;
   int status = pthread_mutex_lock(_mutex);
   assert_status(status == 0, status, "mutex_lock");
   guarantee (_nParked == 0, "invariant") ;
   ++_nParked ;
   // Object.wait(timo) will return because of
   // (a) notification
   // (b) timeout
   // (c) thread.interrupt
   //
   // Thread.interrupt and object.notify{All} both call Event::set.
   // That is, we treat thread.interrupt as a special case of notification.
   // The underlying Solaris implementation, cond_timedwait, admits
   // spurious/premature wakeups, but the JLS/JVM spec prevents the
   // JVM from making those visible to Java code.  As such, we must
   // filter out spurious wakeups.  We assume all ETIME returns are valid.
   //
   // TODO: properly differentiate simultaneous notify+interrupt.
   // In that case, we should propagate the notify to another waiter.
   while (_Event < 0) {
     status = os::Linux::safe_cond_timedwait(_cond, _mutex, &abst);
     if (status != 0 && WorkAroundNPTLTimedWaitHang) {
       pthread_cond_destroy (_cond);
       pthread_cond_init (_cond, NULL) ;
     }
     assert_status(status == 0 || status == EINTR ||
                   status == ETIME || status == ETIMEDOUT,
                   status, "cond_timedwait");
     if (!FilterSpuriousWakeups) break ;                 // previous semantics
     if (status == ETIME || status == ETIMEDOUT) break ;
     // We consume and ignore EINTR and spurious wakeups.
   }
   --_nParked ;
   if (_Event >= 0) {
      ret = OS_OK;
   }
   _Event = 0 ;
   status = pthread_mutex_unlock(_mutex);
   assert_status(status == 0, status, "mutex_unlock");
   assert (_nParked == 0, "invariant") ;
   return ret;
 }
 void os::PlatformEvent::unpark() {
   int v, AnyWaiters ;
   for (;;) {
       v = _Event ;
       if (v > 0) {
          // The LD of _Event could have reordered or be satisfied
          // by a read-aside from this processor's write buffer.
          // To avoid problems execute a barrier and then
          // ratify the value.
          OrderAccess::fence() ;
          if (_Event == v) return ;
          continue ;
       }
       if (Atomic::cmpxchg (v+1, &_Event, v) == v) break ;
   }
   if (v < 0) {
      // Wait for the thread associated with the event to vacate
      int status = pthread_mutex_lock(_mutex);
      assert_status(status == 0, status, "mutex_lock");
      AnyWaiters = _nParked ;
      assert (AnyWaiters == 0 || AnyWaiters == 1, "invariant") ;
      if (AnyWaiters != 0 && WorkAroundNPTLTimedWaitHang) {
         AnyWaiters = 0 ;
         pthread_cond_signal (_cond);
      }
      status = pthread_mutex_unlock(_mutex);
      assert_status(status == 0, status, "mutex_unlock");
      if (AnyWaiters != 0) {
         status = pthread_cond_signal(_cond);
         assert_status(status == 0, status, "cond_signal");
      }
   }
   // Note that we signal() _after dropping the lock for "immortal" Events.
   // This is safe and avoids a common class of  futile wakeups.  In rare
   // circumstances this can cause a thread to return prematurely from
   // cond_{timed}wait() but the spurious wakeup is benign and the victim will
   // simply re-test the condition and re-park itself.
 }
 // JSR166
 // -------------------------------------------------------
 /*
  * The solaris and linux implementations of park/unpark are fairly
  * conservative for now, but can be improved. They currently use a
  * mutex/condvar pair, plus a a count.
  * Park decrements count if > 0, else does a condvar wait.  Unpark
  * sets count to 1 and signals condvar.  Only one thread ever waits
  * on the condvar. Contention seen when trying to park implies that someone
  * is unparking you, so don't wait. And spurious returns are fine, so there
  * is no need to track notifications.
  */
 #define NANOSECS_PER_SEC 1000000000
 #define NANOSECS_PER_MILLISEC 1000000
 #define MAX_SECS 100000000
 /*
  * This code is common to linux and solaris and will be moved to a
  * common place in dolphin.
  *
  * The passed in time value is either a relative time in nanoseconds
  * or an absolute time in milliseconds. Either way it has to be unpacked
  * into suitable seconds and nanoseconds components and stored in the
  * given timespec structure.
  * Given time is a 64-bit value and the time_t used in the timespec is only
  * a signed-32-bit value (except on 64-bit Linux) we have to watch for
  * overflow if times way in the future are given. Further on Solaris versions
  * prior to 10 there is a restriction (see cond_timedwait) that the specified
  * number of seconds, in abstime, is less than current_time  + 100,000,000.
  * As it will be 28 years before "now + 100000000" will overflow we can
  * ignore overflow and just impose a hard-limit on seconds using the value
  * of "now + 100,000,000". This places a limit on the timeout of about 3.17
  * years from "now".
  */
 static void unpackTime(timespec* absTime, bool isAbsolute, jlong time) {
   assert (time > 0, "convertTime");
   struct timeval now;
   int status = gettimeofday(&now, NULL);
   assert(status == 0, "gettimeofday");
   time_t max_secs = now.tv_sec + MAX_SECS;
   if (isAbsolute) {
     jlong secs = time / 1000;
     if (secs > max_secs) {
       absTime->tv_sec = max_secs;
     }
     else {
       absTime->tv_sec = secs;
     }
     absTime->tv_nsec = (time % 1000) * NANOSECS_PER_MILLISEC;
   }
   else {
     jlong secs = time / NANOSECS_PER_SEC;
     if (secs >= MAX_SECS) {
       absTime->tv_sec = max_secs;
       absTime->tv_nsec = 0;
     }
     else {
       absTime->tv_sec = now.tv_sec + secs;
       absTime->tv_nsec = (time % NANOSECS_PER_SEC) + now.tv_usec*1000;
       if (absTime->tv_nsec >= NANOSECS_PER_SEC) {
         absTime->tv_nsec -= NANOSECS_PER_SEC;
         ++absTime->tv_sec; // note: this must be <= max_secs
       }
     }
   }
   assert(absTime->tv_sec >= 0, "tv_sec < 0");
   assert(absTime->tv_sec <= max_secs, "tv_sec > max_secs");
   assert(absTime->tv_nsec >= 0, "tv_nsec < 0");
   assert(absTime->tv_nsec < NANOSECS_PER_SEC, "tv_nsec >= nanos_per_sec");
 }
 void Parker::park(bool isAbsolute, jlong time) {
   // Optional fast-path check:
   // Return immediately if a permit is available.
   if (_counter > 0) {
       _counter = 0 ;
       OrderAccess::fence();
       return ;
   }
   Thread* thread = Thread::current();
   assert(thread->is_Java_thread(), "Must be JavaThread");
   JavaThread *jt = (JavaThread *)thread;
   // Optional optimization -- avoid state transitions if there's an interrupt pending.
   // Check interrupt before trying to wait
   if (Thread::is_interrupted(thread, false)) {
     return;
   }
   // Next, demultiplex/decode time arguments
   timespec absTime;
   if (time < 0) { // don't wait at all
     return;
   }
   if (time > 0) {
     unpackTime(&absTime, isAbsolute, time);
   }
   // Enter safepoint region
   // Beware of deadlocks such as 6317397.
   // The per-thread Parker:: mutex is a classic leaf-lock.
   // In particular a thread must never block on the Threads_lock while
   // holding the Parker:: mutex.  If safepoints are pending both the
   // the ThreadBlockInVM() CTOR and DTOR may grab Threads_lock.
   ThreadBlockInVM tbivm(jt);
   // Don't wait if cannot get lock since interference arises from
   // unblocking.  Also. check interrupt before trying wait
   if (Thread::is_interrupted(thread, false) || pthread_mutex_trylock(_mutex) != 0) {
     return;
   }
   int status ;
   if (_counter > 0)  { // no wait needed
     _counter = 0;
     status = pthread_mutex_unlock(_mutex);
     assert (status == 0, "invariant") ;
     OrderAccess::fence();
     return;
   }
 #ifdef ASSERT
   // Don't catch signals while blocked; let the running threads have the signals.
   // (This allows a debugger to break into the running thread.)
   sigset_t oldsigs;
   sigset_t* allowdebug_blocked = os::Linux::allowdebug_blocked_signals();
   pthread_sigmask(SIG_BLOCK, allowdebug_blocked, &oldsigs);
 #endif
   OSThreadWaitState osts(thread->osthread(), false /* not Object.wait() */);
   jt->set_suspend_equivalent();
   // cleared by handle_special_suspend_equivalent_condition() or java_suspend_self()
   if (time == 0) {
     status = pthread_cond_wait (_cond, _mutex) ;
   } else {
     status = os::Linux::safe_cond_timedwait (_cond, _mutex, &absTime) ;
     if (status != 0 && WorkAroundNPTLTimedWaitHang) {
       pthread_cond_destroy (_cond) ;
       pthread_cond_init    (_cond, NULL);
     }
   }
   assert_status(status == 0 || status == EINTR ||
                 status == ETIME || status == ETIMEDOUT,
                 status, "cond_timedwait");
 #ifdef ASSERT
   pthread_sigmask(SIG_SETMASK, &oldsigs, NULL);
 #endif
   _counter = 0 ;
   status = pthread_mutex_unlock(_mutex) ;
   assert_status(status == 0, status, "invariant") ;
   // If externally suspended while waiting, re-suspend
   if (jt->handle_special_suspend_equivalent_condition()) {
     jt->java_suspend_self();
   }
   OrderAccess::fence();
 }
 void Parker::unpark() {
   int s, status ;
   status = pthread_mutex_lock(_mutex);
   assert (status == 0, "invariant") ;
   s = _counter;
   _counter = 1;
   if (s < 1) {
      if (WorkAroundNPTLTimedWaitHang) {
         status = pthread_cond_signal (_cond) ;
         assert (status == 0, "invariant") ;
         status = pthread_mutex_unlock(_mutex);
         assert (status == 0, "invariant") ;
      } else {
         status = pthread_mutex_unlock(_mutex);
         assert (status == 0, "invariant") ;
         status = pthread_cond_signal (_cond) ;
         assert (status == 0, "invariant") ;
      }
   } else {
     pthread_mutex_unlock(_mutex);
     assert (status == 0, "invariant") ;
   }
 }
 extern char** environ;
 #ifndef __NR_fork
 #define __NR_fork IA32_ONLY(2) IA64_ONLY(not defined) AMD64_ONLY(57)
 #endif
 #ifndef __NR_execve
 #define __NR_execve IA32_ONLY(11) IA64_ONLY(1033) AMD64_ONLY(59)
 #endif
 // Run the specified command in a separate process. Return its exit value,
 // or -1 on failure (e.g. can't fork a new process).
 // Unlike system(), this function can be called from signal handler. It
 // doesn't block SIGINT et al.
 int os::fork_and_exec(char* cmd) {
   const char * argv[4] = {"sh", "-c", cmd, NULL};
   // fork() in LinuxThreads/NPTL is not async-safe. It needs to run
   // pthread_atfork handlers and reset pthread library. All we need is a
   // separate process to execve. Make a direct syscall to fork process.
   // On IA64 there's no fork syscall, we have to use fork() and hope for
   // the best...
   pid_t pid = NOT_IA64(syscall(__NR_fork);)
               IA64_ONLY(fork();)
   if (pid < 0) {
     // fork failed
     return -1;
   } else if (pid == 0) {
     // child process
     // execve() in LinuxThreads will call pthread_kill_other_threads_np()
     // first to kill every thread on the thread list. Because this list is
     // not reset by fork() (see notes above), execve() will instead kill
     // every thread in the parent process. We know this is the only thread
     // in the new process, so make a system call directly.
     // IA64 should use normal execve() from glibc to match the glibc fork()
     // above.
     NOT_IA64(syscall(__NR_execve, "/bin/sh", argv, environ);)
     IA64_ONLY(execve("/bin/sh", (char* const*)argv, environ);)
     // execve failed
     _exit(-1);
   } else  {
     // copied from J2SE ..._waitForProcessExit() in UNIXProcess_md.c; we don't
     // care about the actual exit code, for now.
     int status;
     // Wait for the child process to exit.  This returns immediately if
     // the child has already exited. */
     while (waitpid(pid, &status, 0) < 0) {
         switch (errno) {
         case ECHILD: return 0;
         case EINTR: break;
         default: return -1;
         }
     }
     if (WIFEXITED(status)) {
        // The child exited normally; get its exit code.
        return WEXITSTATUS(status);
     } else if (WIFSIGNALED(status)) {
        // The child exited because of a signal
        // The best value to return is 0x80 + signal number,
        // because that is what all Unix shells do, and because
        // it allows callers to distinguish between process exit and
        // process death by signal.
        return 0x80 + WTERMSIG(status);
     } else {
        // Unknown exit code; pass it through
        return status;
     }
   }
 }
 // is_headless_jre()
 //
 // Test for the existence of libmawt in motif21 or xawt directories
 // in order to report if we are running in a headless jre
 //
 bool os::is_headless_jre() {
     struct stat statbuf;
     char buf[MAXPATHLEN];
     char libmawtpath[MAXPATHLEN];
     const char *xawtstr  = "/xawt/libmawt.so";
     const char *motifstr = "/motif21/libmawt.so";
     char *p;
     // Get path to libjvm.so
     os::jvm_path(buf, sizeof(buf));
     // Get rid of libjvm.so
     p = strrchr(buf, '/');
     if (p == NULL) return false;
     else *p = '\0';
     // Get rid of client or server
     p = strrchr(buf, '/');
     if (p == NULL) return false;
     else *p = '\0';
     // check xawt/libmawt.so
     strcpy(libmawtpath, buf);
     strcat(libmawtpath, xawtstr);
     if (::stat(libmawtpath, &statbuf) == 0) return false;
     // check motif21/libmawt.so
     strcpy(libmawtpath, buf);
     strcat(libmawtpath, motifstr);
     if (::stat(libmawtpath, &statbuf) == 0) return false;
     return true;
 }

Mercurial > jdk8-mips64-public > hotspot / annotate

src/os/linux/vm/os_linux.cpp@c7004d700b49 (annotated)

src/os/linux/vm/os_linux.cpp