jdk8-mips64-public/hotspot: src/share/vm/runtime/os.cpp@1fdb98a17101 (annotated)

src/share/vm/runtime/os.cpp@1fdb98a17101 (annotated)

src/share/vm/runtime/os.cpp

Sat, 19 Jul 2008 17:38:22 -0400

author: coleenp
date: Sat, 19 Jul 2008 17:38:22 -0400
changeset 672: 1fdb98a17101
parent 631: d1605aabd0a1
child 677: d95b224e9f17
permissions: -rw-r--r--

6716785: implicit null checks not triggering with CompressedOops
Summary: allocate alignment-sized page(s) below java heap so that memory accesses at heap_base+1page give signal and cause an implicit null check
Reviewed-by: kvn, jmasa, phh, jcoomes

 /*
  * Copyright 1997-2008 Sun Microsystems, Inc.  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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
  * CA 95054 USA or visit www.sun.com if you need additional information or
  * have any questions.
  *
  */
 # include "incls/_precompiled.incl"
 # include "incls/_os.cpp.incl"
 # include <signal.h>
 OSThread*         os::_starting_thread    = NULL;
 address           os::_polling_page       = NULL;
 volatile int32_t* os::_mem_serialize_page = NULL;
 uintptr_t         os::_serialize_page_mask = 0;
 long              os::_rand_seed          = 1;
 int               os::_processor_count    = 0;
 size_t            os::_page_sizes[os::page_sizes_max];
 #ifndef PRODUCT
 int os::num_mallocs = 0;            // # of calls to malloc/realloc
 size_t os::alloc_bytes = 0;         // # of bytes allocated
 int os::num_frees = 0;              // # of calls to free
 #endif
 // Fill in buffer with current local time as an ISO-8601 string.
 // E.g., yyyy-mm-ddThh:mm:ss-zzzz.
 // Returns buffer, or NULL if it failed.
 // This would mostly be a call to
 //     strftime(...., "%Y-%m-%d" "T" "%H:%M:%S" "%z", ....)
 // except that on Windows the %z behaves badly, so we do it ourselves.
 // Also, people wanted milliseconds on there,
 // and strftime doesn't do milliseconds.
 char* os::iso8601_time(char* buffer, size_t buffer_length) {
   // Output will be of the form "YYYY-MM-DDThh:mm:ss.mmm+zzzz\0"
   //                                      1         2
   //                             12345678901234567890123456789
   static const char* iso8601_format =
     "%04d-%02d-%02dT%02d:%02d:%02d.%03d%c%02d%02d";
   static const size_t needed_buffer = 29;
   // Sanity check the arguments
   if (buffer == NULL) {
     assert(false, "NULL buffer");
     return NULL;
   }
   if (buffer_length < needed_buffer) {
     assert(false, "buffer_length too small");
     return NULL;
   }
   // Get the current time
   jlong milliseconds_since_19700101 = javaTimeMillis();
   const int milliseconds_per_microsecond = 1000;
   const time_t seconds_since_19700101 =
     milliseconds_since_19700101 / milliseconds_per_microsecond;
   const int milliseconds_after_second =
     milliseconds_since_19700101 % milliseconds_per_microsecond;
   // Convert the time value to a tm and timezone variable
   const struct tm *time_struct_temp = localtime(&seconds_since_19700101);
   if (time_struct_temp == NULL) {
     assert(false, "Failed localtime");
     return NULL;
   }
   // Save the results of localtime
   const struct tm time_struct = *time_struct_temp;
   const time_t zone = timezone;
   // If daylight savings time is in effect,
   // we are 1 hour East of our time zone
   const time_t seconds_per_minute = 60;
   const time_t minutes_per_hour = 60;
   const time_t seconds_per_hour = seconds_per_minute * minutes_per_hour;
   time_t UTC_to_local = zone;
   if (time_struct.tm_isdst > 0) {
     UTC_to_local = UTC_to_local - seconds_per_hour;
   }
   // Compute the time zone offset.
   //    localtime(3C) sets timezone to the difference (in seconds)
   //    between UTC and and local time.
   //    ISO 8601 says we need the difference between local time and UTC,
   //    we change the sign of the localtime(3C) result.
   const time_t local_to_UTC = -(UTC_to_local);
   // Then we have to figure out if if we are ahead (+) or behind (-) UTC.
   char sign_local_to_UTC = '+';
   time_t abs_local_to_UTC = local_to_UTC;
   if (local_to_UTC < 0) {
     sign_local_to_UTC = '-';
     abs_local_to_UTC = -(abs_local_to_UTC);
   }
   // Convert time zone offset seconds to hours and minutes.
   const time_t zone_hours = (abs_local_to_UTC / seconds_per_hour);
   const time_t zone_min =
     ((abs_local_to_UTC % seconds_per_hour) / seconds_per_minute);
   // Print an ISO 8601 date and time stamp into the buffer
   const int year = 1900 + time_struct.tm_year;
   const int month = 1 + time_struct.tm_mon;
   const int printed = jio_snprintf(buffer, buffer_length, iso8601_format,
                                    year,
                                    month,
                                    time_struct.tm_mday,
                                    time_struct.tm_hour,
                                    time_struct.tm_min,
                                    time_struct.tm_sec,
                                    milliseconds_after_second,
                                    sign_local_to_UTC,
                                    zone_hours,
                                    zone_min);
   if (printed == 0) {
     assert(false, "Failed jio_printf");
     return NULL;
   }
   return buffer;
 }
 OSReturn os::set_priority(Thread* thread, ThreadPriority p) {
 #ifdef ASSERT
   if (!(!thread->is_Java_thread() ||
          Thread::current() == thread  ||
          Threads_lock->owned_by_self()
          || thread->is_Compiler_thread()
         )) {
     assert(false, "possibility of dangling Thread pointer");
   }
 #endif
   if (p >= MinPriority && p <= MaxPriority) {
     int priority = java_to_os_priority[p];
     return set_native_priority(thread, priority);
   } else {
     assert(false, "Should not happen");
     return OS_ERR;
   }
 }
 OSReturn os::get_priority(const Thread* const thread, ThreadPriority& priority) {
   int p;
   int os_prio;
   OSReturn ret = get_native_priority(thread, &os_prio);
   if (ret != OS_OK) return ret;
   for (p = MaxPriority; p > MinPriority && java_to_os_priority[p] > os_prio; p--) ;
   priority = (ThreadPriority)p;
   return OS_OK;
 }
 // --------------------- sun.misc.Signal (optional) ---------------------
 // SIGBREAK is sent by the keyboard to query the VM state
 #ifndef SIGBREAK
 #define SIGBREAK SIGQUIT
 #endif
 // sigexitnum_pd is a platform-specific special signal used for terminating the Signal thread.
 static void signal_thread_entry(JavaThread* thread, TRAPS) {
   os::set_priority(thread, NearMaxPriority);
   while (true) {
     int sig;
     {
       // FIXME : Currently we have not decieded what should be the status
       //         for this java thread blocked here. Once we decide about
       //         that we should fix this.
       sig = os::signal_wait();
     }
     if (sig == os::sigexitnum_pd()) {
        // Terminate the signal thread
        return;
     }
     switch (sig) {
       case SIGBREAK: {
         // Check if the signal is a trigger to start the Attach Listener - in that
         // case don't print stack traces.
         if (!DisableAttachMechanism && AttachListener::is_init_trigger()) {
           continue;
         }
         // Print stack traces
         // Any SIGBREAK operations added here should make sure to flush
         // the output stream (e.g. tty->flush()) after output.  See 4803766.
         // Each module also prints an extra carriage return after its output.
         VM_PrintThreads op;
         VMThread::execute(&op);
         VM_PrintJNI jni_op;
         VMThread::execute(&jni_op);
         VM_FindDeadlocks op1(tty);
         VMThread::execute(&op1);
         Universe::print_heap_at_SIGBREAK();
         if (PrintClassHistogram) {
           VM_GC_HeapInspection op1(gclog_or_tty, true /* force full GC before heap inspection */);
           VMThread::execute(&op1);
         }
         if (JvmtiExport::should_post_data_dump()) {
           JvmtiExport::post_data_dump();
         }
         break;
       }
       default: {
         // Dispatch the signal to java
         HandleMark hm(THREAD);
         klassOop k = SystemDictionary::resolve_or_null(vmSymbolHandles::sun_misc_Signal(), THREAD);
         KlassHandle klass (THREAD, k);
         if (klass.not_null()) {
           JavaValue result(T_VOID);
           JavaCallArguments args;
           args.push_int(sig);
           JavaCalls::call_static(
             &result,
             klass,
             vmSymbolHandles::dispatch_name(),
             vmSymbolHandles::int_void_signature(),
             &args,
             THREAD
           );
         }
         if (HAS_PENDING_EXCEPTION) {
           // tty is initialized early so we don't expect it to be null, but
           // if it is we can't risk doing an initialization that might
           // trigger additional out-of-memory conditions
           if (tty != NULL) {
             char klass_name[256];
             char tmp_sig_name[16];
             const char* sig_name = "UNKNOWN";
             instanceKlass::cast(PENDING_EXCEPTION->klass())->
               name()->as_klass_external_name(klass_name, 256);
             if (os::exception_name(sig, tmp_sig_name, 16) != NULL)
               sig_name = tmp_sig_name;
             warning("Exception %s occurred dispatching signal %s to handler"
                     "- the VM may need to be forcibly terminated",
                     klass_name, sig_name );
           }
           CLEAR_PENDING_EXCEPTION;
         }
       }
     }
   }
 }
 void os::signal_init() {
   if (!ReduceSignalUsage) {
     // Setup JavaThread for processing signals
     EXCEPTION_MARK;
     klassOop k = SystemDictionary::resolve_or_fail(vmSymbolHandles::java_lang_Thread(), true, CHECK);
     instanceKlassHandle klass (THREAD, k);
     instanceHandle thread_oop = klass->allocate_instance_handle(CHECK);
     const char thread_name[] = "Signal Dispatcher";
     Handle string = java_lang_String::create_from_str(thread_name, CHECK);
     // Initialize thread_oop to put it into the system threadGroup
     Handle thread_group (THREAD, Universe::system_thread_group());
     JavaValue result(T_VOID);
     JavaCalls::call_special(&result, thread_oop,
                            klass,
                            vmSymbolHandles::object_initializer_name(),
                            vmSymbolHandles::threadgroup_string_void_signature(),
                            thread_group,
                            string,
                            CHECK);
     KlassHandle group(THREAD, SystemDictionary::threadGroup_klass());
     JavaCalls::call_special(&result,
                             thread_group,
                             group,
                             vmSymbolHandles::add_method_name(),
                             vmSymbolHandles::thread_void_signature(),
                             thread_oop,         // ARG 1
                             CHECK);
     os::signal_init_pd();
     { MutexLocker mu(Threads_lock);
       JavaThread* signal_thread = new JavaThread(&signal_thread_entry);
       // At this point it may be possible that no osthread was created for the
       // JavaThread due to lack of memory. We would have to throw an exception
       // in that case. However, since this must work and we do not allow
       // exceptions anyway, check and abort if this fails.
       if (signal_thread == NULL || signal_thread->osthread() == NULL) {
         vm_exit_during_initialization("java.lang.OutOfMemoryError",
                                       "unable to create new native thread");
       }
       java_lang_Thread::set_thread(thread_oop(), signal_thread);
       java_lang_Thread::set_priority(thread_oop(), NearMaxPriority);
       java_lang_Thread::set_daemon(thread_oop());
       signal_thread->set_threadObj(thread_oop());
       Threads::add(signal_thread);
       Thread::start(signal_thread);
     }
     // Handle ^BREAK
     os::signal(SIGBREAK, os::user_handler());
   }
 }
 void os::terminate_signal_thread() {
   if (!ReduceSignalUsage)
     signal_notify(sigexitnum_pd());
 }
 // --------------------- loading libraries ---------------------
 typedef jint (JNICALL *JNI_OnLoad_t)(JavaVM *, void *);
 extern struct JavaVM_ main_vm;
 static void* _native_java_library = NULL;
 void* os::native_java_library() {
   if (_native_java_library == NULL) {
     char buffer[JVM_MAXPATHLEN];
     char ebuf[1024];
     // Try to load verify dll first. In 1.3 java dll depends on it and is not always
     // able to find it when the loading executable is outside the JDK.
     // In order to keep working with 1.2 we ignore any loading errors.
     hpi::dll_build_name(buffer, sizeof(buffer), Arguments::get_dll_dir(), "verify");
     hpi::dll_load(buffer, ebuf, sizeof(ebuf));
     // Load java dll
     hpi::dll_build_name(buffer, sizeof(buffer), Arguments::get_dll_dir(), "java");
     _native_java_library = hpi::dll_load(buffer, ebuf, sizeof(ebuf));
     if (_native_java_library == NULL) {
       vm_exit_during_initialization("Unable to load native library", ebuf);
     }
     // The JNI_OnLoad handling is normally done by method load in java.lang.ClassLoader$NativeLibrary,
     // but the VM loads the base library explicitly so we have to check for JNI_OnLoad as well
     const char *onLoadSymbols[] = JNI_ONLOAD_SYMBOLS;
     JNI_OnLoad_t JNI_OnLoad = CAST_TO_FN_PTR(JNI_OnLoad_t, hpi::dll_lookup(_native_java_library, onLoadSymbols[0]));
     if (JNI_OnLoad != NULL) {
       JavaThread* thread = JavaThread::current();
       ThreadToNativeFromVM ttn(thread);
       HandleMark hm(thread);
       jint ver = (*JNI_OnLoad)(&main_vm, NULL);
       if (!Threads::is_supported_jni_version_including_1_1(ver)) {
         vm_exit_during_initialization("Unsupported JNI version");
       }
     }
   }
   return _native_java_library;
 }
 // --------------------- heap allocation utilities ---------------------
 char *os::strdup(const char *str) {
   size_t size = strlen(str);
   char *dup_str = (char *)malloc(size + 1);
   if (dup_str == NULL) return NULL;
   strcpy(dup_str, str);
   return dup_str;
 }
 #ifdef ASSERT
 #define space_before             (MallocCushion + sizeof(double))
 #define space_after              MallocCushion
 #define size_addr_from_base(p)   (size_t*)(p + space_before - sizeof(size_t))
 #define size_addr_from_obj(p)    ((size_t*)p - 1)
 // MallocCushion: size of extra cushion allocated around objects with +UseMallocOnly
 // NB: cannot be debug variable, because these aren't set from the command line until
 // *after* the first few allocs already happened
 #define MallocCushion            16
 #else
 #define space_before             0
 #define space_after              0
 #define size_addr_from_base(p)   should not use w/o ASSERT
 #define size_addr_from_obj(p)    should not use w/o ASSERT
 #define MallocCushion            0
 #endif
 #define paranoid                 0  /* only set to 1 if you suspect checking code has bug */
 #ifdef ASSERT
 inline size_t get_size(void* obj) {
   size_t size = *size_addr_from_obj(obj);
   if (size < 0 )
     fatal2("free: size field of object #%p was overwritten (%lu)", obj, size);
   return size;
 }
 u_char* find_cushion_backwards(u_char* start) {
   u_char* p = start;
   while (p[ 0] != badResourceValue || p[-1] != badResourceValue ||
          p[-2] != badResourceValue || p[-3] != badResourceValue) p--;
   // ok, we have four consecutive marker bytes; find start
   u_char* q = p - 4;
   while (*q == badResourceValue) q--;
   return q + 1;
 }
 u_char* find_cushion_forwards(u_char* start) {
   u_char* p = start;
   while (p[0] != badResourceValue || p[1] != badResourceValue ||
          p[2] != badResourceValue || p[3] != badResourceValue) p++;
   // ok, we have four consecutive marker bytes; find end of cushion
   u_char* q = p + 4;
   while (*q == badResourceValue) q++;
   return q - MallocCushion;
 }
 void print_neighbor_blocks(void* ptr) {
   // find block allocated before ptr (not entirely crash-proof)
   if (MallocCushion < 4) {
     tty->print_cr("### cannot find previous block (MallocCushion < 4)");
     return;
   }
   u_char* start_of_this_block = (u_char*)ptr - space_before;
   u_char* end_of_prev_block_data = start_of_this_block - space_after -1;
   // look for cushion in front of prev. block
   u_char* start_of_prev_block = find_cushion_backwards(end_of_prev_block_data);
   ptrdiff_t size = *size_addr_from_base(start_of_prev_block);
   u_char* obj = start_of_prev_block + space_before;
   if (size <= 0 ) {
     // start is bad; mayhave been confused by OS data inbetween objects
     // search one more backwards
     start_of_prev_block = find_cushion_backwards(start_of_prev_block);
     size = *size_addr_from_base(start_of_prev_block);
     obj = start_of_prev_block + space_before;
   }
   if (start_of_prev_block + space_before + size + space_after == start_of_this_block) {
     tty->print_cr("### previous object: %p (%ld bytes)", obj, size);
   } else {
     tty->print_cr("### previous object (not sure if correct): %p (%ld bytes)", obj, size);
   }
   // now find successor block
   u_char* start_of_next_block = (u_char*)ptr + *size_addr_from_obj(ptr) + space_after;
   start_of_next_block = find_cushion_forwards(start_of_next_block);
   u_char* next_obj = start_of_next_block + space_before;
   ptrdiff_t next_size = *size_addr_from_base(start_of_next_block);
   if (start_of_next_block[0] == badResourceValue &&
       start_of_next_block[1] == badResourceValue &&
       start_of_next_block[2] == badResourceValue &&
       start_of_next_block[3] == badResourceValue) {
     tty->print_cr("### next object: %p (%ld bytes)", next_obj, next_size);
   } else {
     tty->print_cr("### next object (not sure if correct): %p (%ld bytes)", next_obj, next_size);
   }
 }
 void report_heap_error(void* memblock, void* bad, const char* where) {
   tty->print_cr("## nof_mallocs = %d, nof_frees = %d", os::num_mallocs, os::num_frees);
   tty->print_cr("## memory stomp: byte at %p %s object %p", bad, where, memblock);
   print_neighbor_blocks(memblock);
   fatal("memory stomping error");
 }
 void verify_block(void* memblock) {
   size_t size = get_size(memblock);
   if (MallocCushion) {
     u_char* ptr = (u_char*)memblock - space_before;
     for (int i = 0; i < MallocCushion; i++) {
       if (ptr[i] != badResourceValue) {
         report_heap_error(memblock, ptr+i, "in front of");
       }
     }
     u_char* end = (u_char*)memblock + size + space_after;
     for (int j = -MallocCushion; j < 0; j++) {
       if (end[j] != badResourceValue) {
         report_heap_error(memblock, end+j, "after");
       }
     }
   }
 }
 #endif
 void* os::malloc(size_t size) {
   NOT_PRODUCT(num_mallocs++);
   NOT_PRODUCT(alloc_bytes += size);
   if (size == 0) {
     // return a valid pointer if size is zero
     // if NULL is returned the calling functions assume out of memory.
     size = 1;
   }
   NOT_PRODUCT(if (MallocVerifyInterval > 0) check_heap());
   u_char* ptr = (u_char*)::malloc(size + space_before + space_after);
 #ifdef ASSERT
   if (ptr == NULL) return NULL;
   if (MallocCushion) {
     for (u_char* p = ptr; p < ptr + MallocCushion; p++) *p = (u_char)badResourceValue;
     u_char* end = ptr + space_before + size;
     for (u_char* pq = ptr+MallocCushion; pq < end; pq++) *pq = (u_char)uninitBlockPad;
     for (u_char* q = end; q < end + MallocCushion; q++) *q = (u_char)badResourceValue;
   }
   // put size just before data
   *size_addr_from_base(ptr) = size;
 #endif
   u_char* memblock = ptr + space_before;
   if ((intptr_t)memblock == (intptr_t)MallocCatchPtr) {
     tty->print_cr("os::malloc caught, %lu bytes --> %p", size, memblock);
     breakpoint();
   }
   debug_only(if (paranoid) verify_block(memblock));
   if (PrintMalloc && tty != NULL) tty->print_cr("os::malloc %lu bytes --> %p", size, memblock);
   return memblock;
 }
 void* os::realloc(void *memblock, size_t size) {
   NOT_PRODUCT(num_mallocs++);
   NOT_PRODUCT(alloc_bytes += size);
 #ifndef ASSERT
   return ::realloc(memblock, size);
 #else
   if (memblock == NULL) {
     return os::malloc(size);
   }
   if ((intptr_t)memblock == (intptr_t)MallocCatchPtr) {
     tty->print_cr("os::realloc caught %p", memblock);
     breakpoint();
   }
   verify_block(memblock);
   NOT_PRODUCT(if (MallocVerifyInterval > 0) check_heap());
   if (size == 0) return NULL;
   // always move the block
   void* ptr = malloc(size);
   if (PrintMalloc) tty->print_cr("os::remalloc %lu bytes, %p --> %p", size, memblock, ptr);
   // Copy to new memory if malloc didn't fail
   if ( ptr != NULL ) {
     memcpy(ptr, memblock, MIN2(size, get_size(memblock)));
     if (paranoid) verify_block(ptr);
     if ((intptr_t)ptr == (intptr_t)MallocCatchPtr) {
       tty->print_cr("os::realloc caught, %lu bytes --> %p", size, ptr);
       breakpoint();
     }
     free(memblock);
   }
   return ptr;
 #endif
 }
 void  os::free(void *memblock) {
   NOT_PRODUCT(num_frees++);
 #ifdef ASSERT
   if (memblock == NULL) return;
   if ((intptr_t)memblock == (intptr_t)MallocCatchPtr) {
     if (tty != NULL) tty->print_cr("os::free caught %p", memblock);
     breakpoint();
   }
   verify_block(memblock);
   if (PrintMalloc && tty != NULL)
     // tty->print_cr("os::free %p", memblock);
     fprintf(stderr, "os::free %p\n", memblock);
   NOT_PRODUCT(if (MallocVerifyInterval > 0) check_heap());
   // Added by detlefs.
   if (MallocCushion) {
     u_char* ptr = (u_char*)memblock - space_before;
     for (u_char* p = ptr; p < ptr + MallocCushion; p++) {
       guarantee(*p == badResourceValue,
                 "Thing freed should be malloc result.");
       *p = (u_char)freeBlockPad;
     }
     size_t size = get_size(memblock);
     u_char* end = ptr + space_before + size;
     for (u_char* q = end; q < end + MallocCushion; q++) {
       guarantee(*q == badResourceValue,
                 "Thing freed should be malloc result.");
       *q = (u_char)freeBlockPad;
     }
   }
 #endif
   ::free((char*)memblock - space_before);
 }
 void os::init_random(long initval) {
   _rand_seed = initval;
 }
 long os::random() {
   /* standard, well-known linear congruential random generator with
    * next_rand = (16807*seed) mod (2**31-1)
    * see
    * (1) "Random Number Generators: Good Ones Are Hard to Find",
    *      S.K. Park and K.W. Miller, Communications of the ACM 31:10 (Oct 1988),
    * (2) "Two Fast Implementations of the 'Minimal Standard' Random
    *     Number Generator", David G. Carta, Comm. ACM 33, 1 (Jan 1990), pp. 87-88.
   */
   const long a = 16807;
   const unsigned long m = 2147483647;
   const long q = m / a;        assert(q == 127773, "weird math");
   const long r = m % a;        assert(r == 2836, "weird math");
   // compute az=2^31p+q
   unsigned long lo = a * (long)(_rand_seed & 0xFFFF);
   unsigned long hi = a * (long)((unsigned long)_rand_seed >> 16);
   lo += (hi & 0x7FFF) << 16;
   // if q overflowed, ignore the overflow and increment q
   if (lo > m) {
     lo &= m;
     ++lo;
   }
   lo += hi >> 15;
   // if (p+q) overflowed, ignore the overflow and increment (p+q)
   if (lo > m) {
     lo &= m;
     ++lo;
   }
   return (_rand_seed = lo);
 }
 // The INITIALIZED state is distinguished from the SUSPENDED state because the
 // conditions in which a thread is first started are different from those in which
 // a suspension is resumed.  These differences make it hard for us to apply the
 // tougher checks when starting threads that we want to do when resuming them.
 // However, when start_thread is called as a result of Thread.start, on a Java
 // thread, the operation is synchronized on the Java Thread object.  So there
 // cannot be a race to start the thread and hence for the thread to exit while
 // we are working on it.  Non-Java threads that start Java threads either have
 // to do so in a context in which races are impossible, or should do appropriate
 // locking.
 void os::start_thread(Thread* thread) {
   // guard suspend/resume
   MutexLockerEx ml(thread->SR_lock(), Mutex::_no_safepoint_check_flag);
   OSThread* osthread = thread->osthread();
   osthread->set_state(RUNNABLE);
   pd_start_thread(thread);
 }
 //---------------------------------------------------------------------------
 // Helper functions for fatal error handler
 void os::print_hex_dump(outputStream* st, address start, address end, int unitsize) {
   assert(unitsize == 1 || unitsize == 2 || unitsize == 4 || unitsize == 8, "just checking");
   int cols = 0;
   int cols_per_line = 0;
   switch (unitsize) {
     case 1: cols_per_line = 16; break;
     case 2: cols_per_line = 8;  break;
     case 4: cols_per_line = 4;  break;
     case 8: cols_per_line = 2;  break;
     default: return;
   }
   address p = start;
   st->print(PTR_FORMAT ":   ", start);
   while (p < end) {
     switch (unitsize) {
       case 1: st->print("%02x", *(u1*)p); break;
       case 2: st->print("%04x", *(u2*)p); break;
       case 4: st->print("%08x", *(u4*)p); break;
       case 8: st->print("%016" FORMAT64_MODIFIER "x", *(u8*)p); break;
     }
     p += unitsize;
     cols++;
     if (cols >= cols_per_line && p < end) {
        cols = 0;
        st->cr();
        st->print(PTR_FORMAT ":   ", p);
     } else {
        st->print(" ");
     }
   }
   st->cr();
 }
 void os::print_environment_variables(outputStream* st, const char** env_list,
                                      char* buffer, int len) {
   if (env_list) {
     st->print_cr("Environment Variables:");
     for (int i = 0; env_list[i] != NULL; i++) {
       if (getenv(env_list[i], buffer, len)) {
         st->print(env_list[i]);
         st->print("=");
         st->print_cr(buffer);
       }
     }
   }
 }
 void os::print_cpu_info(outputStream* st) {
   // cpu
   st->print("CPU:");
   st->print("total %d", os::processor_count());
   // It's not safe to query number of active processors after crash
   // st->print("(active %d)", os::active_processor_count());
   st->print(" %s", VM_Version::cpu_features());
   st->cr();
 }
 void os::print_date_and_time(outputStream *st) {
   time_t tloc;
   (void)time(&tloc);
   st->print("time: %s", ctime(&tloc));  // ctime adds newline.
   double t = os::elapsedTime();
   // NOTE: It tends to crash after a SEGV if we want to printf("%f",...) in
   //       Linux. Must be a bug in glibc ? Workaround is to round "t" to int
   //       before printf. We lost some precision, but who cares?
   st->print_cr("elapsed time: %d seconds", (int)t);
 }
 // Looks like all platforms except IA64 can use the same function to check
 // if C stack is walkable beyond current frame. The check for fp() is not
 // necessary on Sparc, but it's harmless.
 bool os::is_first_C_frame(frame* fr) {
 #ifdef IA64
   // In order to walk native frames on Itanium, we need to access the unwind
   // table, which is inside ELF. We don't want to parse ELF after fatal error,
   // so return true for IA64. If we need to support C stack walking on IA64,
   // this function needs to be moved to CPU specific files, as fp() on IA64
   // is register stack, which grows towards higher memory address.
   return true;
 #endif
   // Load up sp, fp, sender sp and sender fp, check for reasonable values.
   // Check usp first, because if that's bad the other accessors may fault
   // on some architectures.  Ditto ufp second, etc.
   uintptr_t fp_align_mask = (uintptr_t)(sizeof(address)-1);
   // sp on amd can be 32 bit aligned.
   uintptr_t sp_align_mask = (uintptr_t)(sizeof(int)-1);
   uintptr_t usp    = (uintptr_t)fr->sp();
   if ((usp & sp_align_mask) != 0) return true;
   uintptr_t ufp    = (uintptr_t)fr->fp();
   if ((ufp & fp_align_mask) != 0) return true;
   uintptr_t old_sp = (uintptr_t)fr->sender_sp();
   if ((old_sp & sp_align_mask) != 0) return true;
   if (old_sp == 0 || old_sp == (uintptr_t)-1) return true;
   uintptr_t old_fp = (uintptr_t)fr->link();
   if ((old_fp & fp_align_mask) != 0) return true;
   if (old_fp == 0 || old_fp == (uintptr_t)-1 || old_fp == ufp) return true;
   // stack grows downwards; if old_fp is below current fp or if the stack
   // frame is too large, either the stack is corrupted or fp is not saved
   // on stack (i.e. on x86, ebp may be used as general register). The stack
   // is not walkable beyond current frame.
   if (old_fp < ufp) return true;
   if (old_fp - ufp > 64 * K) return true;
   return false;
 }
 #ifdef ASSERT
 extern "C" void test_random() {
   const double m = 2147483647;
   double mean = 0.0, variance = 0.0, t;
   long reps = 10000;
   unsigned long seed = 1;
   tty->print_cr("seed %ld for %ld repeats...", seed, reps);
   os::init_random(seed);
   long num;
   for (int k = 0; k < reps; k++) {
     num = os::random();
     double u = (double)num / m;
     assert(u >= 0.0 && u <= 1.0, "bad random number!");
     // calculate mean and variance of the random sequence
     mean += u;
     variance += (u*u);
   }
   mean /= reps;
   variance /= (reps - 1);
   assert(num == 1043618065, "bad seed");
   tty->print_cr("mean of the 1st 10000 numbers: %f", mean);
   tty->print_cr("variance of the 1st 10000 numbers: %f", variance);
   const double eps = 0.0001;
   t = fabsd(mean - 0.5018);
   assert(t < eps, "bad mean");
   t = (variance - 0.3355) < 0.0 ? -(variance - 0.3355) : variance - 0.3355;
   assert(t < eps, "bad variance");
 }
 #endif
 // Set up the boot classpath.
 char* os::format_boot_path(const char* format_string,
                            const char* home,
                            int home_len,
                            char fileSep,
                            char pathSep) {
     assert((fileSep == '/' && pathSep == ':') ||
            (fileSep == '\\' && pathSep == ';'), "unexpected seperator chars");
     // Scan the format string to determine the length of the actual
     // boot classpath, and handle platform dependencies as well.
     int formatted_path_len = 0;
     const char* p;
     for (p = format_string; *p != 0; ++p) {
         if (*p == '%') formatted_path_len += home_len - 1;
         ++formatted_path_len;
     }
     char* formatted_path = NEW_C_HEAP_ARRAY(char, formatted_path_len + 1);
     if (formatted_path == NULL) {
         return NULL;
     }
     // Create boot classpath from format, substituting separator chars and
     // java home directory.
     char* q = formatted_path;
     for (p = format_string; *p != 0; ++p) {
         switch (*p) {
         case '%':
             strcpy(q, home);
             q += home_len;
             break;
         case '/':
             *q++ = fileSep;
             break;
         case ':':
             *q++ = pathSep;
             break;
         default:
             *q++ = *p;
         }
     }
     *q = '\0';
     assert((q - formatted_path) == formatted_path_len, "formatted_path size botched");
     return formatted_path;
 }
 bool os::set_boot_path(char fileSep, char pathSep) {
     const char* home = Arguments::get_java_home();
     int home_len = (int)strlen(home);
     static const char* meta_index_dir_format = "%/lib/";
     static const char* meta_index_format = "%/lib/meta-index";
     char* meta_index = format_boot_path(meta_index_format, home, home_len, fileSep, pathSep);
     if (meta_index == NULL) return false;
     char* meta_index_dir = format_boot_path(meta_index_dir_format, home, home_len, fileSep, pathSep);
     if (meta_index_dir == NULL) return false;
     Arguments::set_meta_index_path(meta_index, meta_index_dir);
     // Any modification to the JAR-file list, for the boot classpath must be
     // aligned with install/install/make/common/Pack.gmk. Note: boot class
     // path class JARs, are stripped for StackMapTable to reduce download size.
     static const char classpath_format[] =
         "%/lib/resources.jar:"
         "%/lib/rt.jar:"
         "%/lib/sunrsasign.jar:"
         "%/lib/jsse.jar:"
         "%/lib/jce.jar:"
         "%/lib/charsets.jar:"
         "%/classes";
     char* sysclasspath = format_boot_path(classpath_format, home, home_len, fileSep, pathSep);
     if (sysclasspath == NULL) return false;
     Arguments::set_sysclasspath(sysclasspath);
     return true;
 }
 void os::set_memory_serialize_page(address page) {
   int count = log2_intptr(sizeof(class JavaThread)) - log2_intptr(64);
   _mem_serialize_page = (volatile int32_t *)page;
   // We initialize the serialization page shift count here
   // We assume a cache line size of 64 bytes
   assert(SerializePageShiftCount == count,
          "thread size changed, fix SerializePageShiftCount constant");
   set_serialize_page_mask((uintptr_t)(vm_page_size() - sizeof(int32_t)));
 }
 static volatile intptr_t SerializePageLock = 0;
 // This method is called from signal handler when SIGSEGV occurs while the current
 // thread tries to store to the "read-only" memory serialize page during state
 // transition.
 void os::block_on_serialize_page_trap() {
   if (TraceSafepoint) {
     tty->print_cr("Block until the serialize page permission restored");
   }
   // When VMThread is holding the SerializePageLock during modifying the
   // access permission of the memory serialize page, the following call
   // will block until the permission of that page is restored to rw.
   // Generally, it is unsafe to manipulate locks in signal handlers, but in
   // this case, it's OK as the signal is synchronous and we know precisely when
   // it can occur.
   Thread::muxAcquire(&SerializePageLock, "set_memory_serialize_page");
   Thread::muxRelease(&SerializePageLock);
 }
 // Serialize all thread state variables
 void os::serialize_thread_states() {
   // On some platforms such as Solaris & Linux, the time duration of the page
   // permission restoration is observed to be much longer than expected  due to
   // scheduler starvation problem etc. To avoid the long synchronization
   // time and expensive page trap spinning, 'SerializePageLock' is used to block
   // the mutator thread if such case is encountered. See bug 6546278 for details.
   Thread::muxAcquire(&SerializePageLock, "serialize_thread_states");
   os::protect_memory((char *)os::get_memory_serialize_page(),
                      os::vm_page_size(), MEM_PROT_READ, /*is_committed*/true );
   os::unguard_memory((char *)os::get_memory_serialize_page(), os::vm_page_size());
   Thread::muxRelease(&SerializePageLock);
 }
 // Returns true if the current stack pointer is above the stack shadow
 // pages, false otherwise.
 bool os::stack_shadow_pages_available(Thread *thread, methodHandle method) {
   assert(StackRedPages > 0 && StackYellowPages > 0,"Sanity check");
   address sp = current_stack_pointer();
   // Check if we have StackShadowPages above the yellow zone.  This parameter
   // is dependant on the depth of the maximum VM call stack possible from
   // the handler for stack overflow.  'instanceof' in the stack overflow
   // handler or a println uses at least 8k stack of VM and native code
   // respectively.
   const int framesize_in_bytes =
     Interpreter::size_top_interpreter_activation(method()) * wordSize;
   int reserved_area = ((StackShadowPages + StackRedPages + StackYellowPages)
                       * vm_page_size()) + framesize_in_bytes;
   // The very lower end of the stack
   address stack_limit = thread->stack_base() - thread->stack_size();
   return (sp > (stack_limit + reserved_area));
 }
 size_t os::page_size_for_region(size_t region_min_size, size_t region_max_size,
                                 uint min_pages)
 {
   assert(min_pages > 0, "sanity");
   if (UseLargePages) {
     const size_t max_page_size = region_max_size / min_pages;
     for (unsigned int i = 0; _page_sizes[i] != 0; ++i) {
       const size_t sz = _page_sizes[i];
       const size_t mask = sz - 1;
       if ((region_min_size & mask) == 0 && (region_max_size & mask) == 0) {
         // The largest page size with no fragmentation.
         return sz;
       }
       if (sz <= max_page_size) {
         // The largest page size that satisfies the min_pages requirement.
         return sz;
       }
     }
   }
   return vm_page_size();
 }
 #ifndef PRODUCT
 void os::trace_page_sizes(const char* str, const size_t region_min_size,
                           const size_t region_max_size, const size_t page_size,
                           const char* base, const size_t size)
 {
   if (TracePageSizes) {
     tty->print_cr("%s:  min=" SIZE_FORMAT " max=" SIZE_FORMAT
                   " pg_sz=" SIZE_FORMAT " base=" PTR_FORMAT
                   " size=" SIZE_FORMAT,
                   str, region_min_size, region_max_size,
                   page_size, base, size);
   }
 }
 #endif  // #ifndef PRODUCT
 // This is the working definition of a server class machine:
 // >= 2 physical CPU's and >=2GB of memory, with some fuzz
 // because the graphics memory (?) sometimes masks physical memory.
 // If you want to change the definition of a server class machine
 // on some OS or platform, e.g., >=4GB on Windohs platforms,
 // then you'll have to parameterize this method based on that state,
 // as was done for logical processors here, or replicate and
 // specialize this method for each platform.  (Or fix os to have
 // some inheritance structure and use subclassing.  Sigh.)
 // If you want some platform to always or never behave as a server
 // class machine, change the setting of AlwaysActAsServerClassMachine
 // and NeverActAsServerClassMachine in globals*.hpp.
 bool os::is_server_class_machine() {
   // First check for the early returns
   if (NeverActAsServerClassMachine) {
     return false;
   }
   if (AlwaysActAsServerClassMachine) {
     return true;
   }
   // Then actually look at the machine
   bool         result            = false;
   const unsigned int    server_processors = 2;
   const julong server_memory     = 2UL * G;
   // We seem not to get our full complement of memory.
   //     We allow some part (1/8?) of the memory to be "missing",
   //     based on the sizes of DIMMs, and maybe graphics cards.
   const julong missing_memory   = 256UL * M;
   /* Is this a server class machine? */
   if ((os::active_processor_count() >= (int)server_processors) &&
       (os::physical_memory() >= (server_memory - missing_memory))) {
     const unsigned int logical_processors =
       VM_Version::logical_processors_per_package();
     if (logical_processors > 1) {
       const unsigned int physical_packages =
         os::active_processor_count() / logical_processors;
       if (physical_packages > server_processors) {
         result = true;
       }
     } else {
       result = true;
     }
   }
   return result;
 }

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src/share/vm/runtime/os.cpp@1fdb98a17101 (annotated)

src/share/vm/runtime/os.cpp