src/share/vm/runtime/os.hpp

Wed, 20 Aug 2008 15:41:36 -0700

author
ysr
date
Wed, 20 Aug 2008 15:41:36 -0700
changeset 735
bfcb639d5bca
parent 677
d95b224e9f17
child 791
1ee8caae33af
permissions
-rw-r--r--

6739357: CMS: Switch off CMSPrecleanRefLists1 until 6722113 can be fixed
Summary: Temporarily switch off the precleaning of Reference lists completely until related issues are fixed in 6722113.
Reviewed-by: jmasa, poonam, tonyp

     1 /*
     2  * Copyright 1997-2008 Sun Microsystems, Inc.  All Rights Reserved.
     3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
     4  *
     5  * This code is free software; you can redistribute it and/or modify it
     6  * under the terms of the GNU General Public License version 2 only, as
     7  * published by the Free Software Foundation.
     8  *
     9  * This code is distributed in the hope that it will be useful, but WITHOUT
    10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
    11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
    12  * version 2 for more details (a copy is included in the LICENSE file that
    13  * accompanied this code).
    14  *
    15  * You should have received a copy of the GNU General Public License version
    16  * 2 along with this work; if not, write to the Free Software Foundation,
    17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
    18  *
    19  * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
    20  * CA 95054 USA or visit www.sun.com if you need additional information or
    21  * have any questions.
    22  *
    23  */
    25 // os defines the interface to operating system; this includes traditional
    26 // OS services (time, I/O) as well as other functionality with system-
    27 // dependent code.
    29 typedef void (*dll_func)(...);
    31 class Thread;
    32 class JavaThread;
    33 class Event;
    34 class DLL;
    35 class FileHandle;
    36 template<class E> class GrowableArray;
    38 // %%%%% Moved ThreadState, START_FN, OSThread to new osThread.hpp. -- Rose
    40 // Platform-independent error return values from OS functions
    41 enum OSReturn {
    42   OS_OK         =  0,        // Operation was successful
    43   OS_ERR        = -1,        // Operation failed
    44   OS_INTRPT     = -2,        // Operation was interrupted
    45   OS_TIMEOUT    = -3,        // Operation timed out
    46   OS_NOMEM      = -5,        // Operation failed for lack of memory
    47   OS_NORESOURCE = -6         // Operation failed for lack of nonmemory resource
    48 };
    50 enum ThreadPriority {        // JLS 20.20.1-3
    51   NoPriority       = -1,     // Initial non-priority value
    52   MinPriority      =  1,     // Minimum priority
    53   NormPriority     =  5,     // Normal (non-daemon) priority
    54   NearMaxPriority  =  9,     // High priority, used for VMThread
    55   MaxPriority      = 10      // Highest priority, used for WatcherThread
    56                              // ensures that VMThread doesn't starve profiler
    57 };
    59 // Typedef for structured exception handling support
    60 typedef void (*java_call_t)(JavaValue* value, methodHandle* method, JavaCallArguments* args, Thread* thread);
    62 class os: AllStatic {
    63  private:
    64   enum { page_sizes_max = 9 }; // Size of _page_sizes array (8 plus a sentinel)
    66   static OSThread*          _starting_thread;
    67   static address            _polling_page;
    68   static volatile int32_t * _mem_serialize_page;
    69   static uintptr_t          _serialize_page_mask;
    70   static size_t             _page_sizes[page_sizes_max];
    72   static void init_page_sizes(size_t default_page_size) {
    73     _page_sizes[0] = default_page_size;
    74     _page_sizes[1] = 0; // sentinel
    75   }
    77  public:
    79   static void init(void);                       // Called before command line parsing
    80   static jint init_2(void);                    // Called after command line parsing
    82   // File names are case-insensitive on windows only
    83   // Override me as needed
    84   static int    file_name_strcmp(const char* s1, const char* s2);
    86   static bool getenv(const char* name, char* buffer, int len);
    87   static bool have_special_privileges();
    89   static jlong  javaTimeMillis();
    90   static jlong  javaTimeNanos();
    91   static void   javaTimeNanos_info(jvmtiTimerInfo *info_ptr);
    92   static void   run_periodic_checks();
    95   // Returns the elapsed time in seconds since the vm started.
    96   static double elapsedTime();
    98   // Returns real time in seconds since an arbitrary point
    99   // in the past.
   100   static bool getTimesSecs(double* process_real_time,
   101                            double* process_user_time,
   102                            double* process_system_time);
   104   // Interface to the performance counter
   105   static jlong elapsed_counter();
   106   static jlong elapsed_frequency();
   108   // Return current local time in a string (YYYY-MM-DD HH:MM:SS).
   109   // It is MT safe, but not async-safe, as reading time zone
   110   // information may require a lock on some platforms.
   111   static char* local_time_string(char *buf, size_t buflen);
   112   // Fill in buffer with current local time as an ISO-8601 string.
   113   // E.g., YYYY-MM-DDThh:mm:ss.mmm+zzzz.
   114   // Returns buffer, or NULL if it failed.
   115   static char* iso8601_time(char* buffer, size_t buffer_length);
   117   // Interface for detecting multiprocessor system
   118   static inline bool is_MP() {
   119     assert(_processor_count > 0, "invalid processor count");
   120     return _processor_count > 1;
   121   }
   122   static julong available_memory();
   123   static julong physical_memory();
   124   static julong allocatable_physical_memory(julong size);
   125   static bool is_server_class_machine();
   127   // number of CPUs
   128   static int processor_count() {
   129     return _processor_count;
   130   }
   132   // Returns the number of CPUs this process is currently allowed to run on.
   133   // Note that on some OSes this can change dynamically.
   134   static int active_processor_count();
   136   // Bind processes to processors.
   137   //     This is a two step procedure:
   138   //     first you generate a distribution of processes to processors,
   139   //     then you bind processes according to that distribution.
   140   // Compute a distribution for number of processes to processors.
   141   //    Stores the processor id's into the distribution array argument.
   142   //    Returns true if it worked, false if it didn't.
   143   static bool distribute_processes(uint length, uint* distribution);
   144   // Binds the current process to a processor.
   145   //    Returns true if it worked, false if it didn't.
   146   static bool bind_to_processor(uint processor_id);
   148   // Interface for stack banging (predetect possible stack overflow for
   149   // exception processing)  There are guard pages, and above that shadow
   150   // pages for stack overflow checking.
   151   static bool uses_stack_guard_pages();
   152   static bool allocate_stack_guard_pages();
   153   static void bang_stack_shadow_pages();
   154   static bool stack_shadow_pages_available(Thread *thread, methodHandle method);
   156   // OS interface to Virtual Memory
   158   // Return the default page size.
   159   static int    vm_page_size();
   161   // Return the page size to use for a region of memory.  The min_pages argument
   162   // is a hint intended to limit fragmentation; it says the returned page size
   163   // should be <= region_max_size / min_pages.  Because min_pages is a hint,
   164   // this routine may return a size larger than region_max_size / min_pages.
   165   //
   166   // The current implementation ignores min_pages if a larger page size is an
   167   // exact multiple of both region_min_size and region_max_size.  This allows
   168   // larger pages to be used when doing so would not cause fragmentation; in
   169   // particular, a single page can be used when region_min_size ==
   170   // region_max_size == a supported page size.
   171   static size_t page_size_for_region(size_t region_min_size,
   172                                      size_t region_max_size,
   173                                      uint min_pages);
   175   // Method for tracing page sizes returned by the above method; enabled by
   176   // TracePageSizes.  The region_{min,max}_size parameters should be the values
   177   // passed to page_size_for_region() and page_size should be the result of that
   178   // call.  The (optional) base and size parameters should come from the
   179   // ReservedSpace base() and size() methods.
   180   static void trace_page_sizes(const char* str, const size_t region_min_size,
   181                                const size_t region_max_size,
   182                                const size_t page_size,
   183                                const char* base = NULL,
   184                                const size_t size = 0) PRODUCT_RETURN;
   186   static int    vm_allocation_granularity();
   187   static char*  reserve_memory(size_t bytes, char* addr = 0,
   188                                size_t alignment_hint = 0);
   189   static char*  attempt_reserve_memory_at(size_t bytes, char* addr);
   190   static void   split_reserved_memory(char *base, size_t size,
   191                                       size_t split, bool realloc);
   192   static bool   commit_memory(char* addr, size_t bytes);
   193   static bool   commit_memory(char* addr, size_t size, size_t alignment_hint);
   194   static bool   uncommit_memory(char* addr, size_t bytes);
   195   static bool   release_memory(char* addr, size_t bytes);
   197   enum ProtType { MEM_PROT_NONE, MEM_PROT_READ, MEM_PROT_RW, MEM_PROT_RWX };
   198   static bool   protect_memory(char* addr, size_t bytes, ProtType prot,
   199                                bool is_committed = false);
   201   static bool   guard_memory(char* addr, size_t bytes);
   202   static bool   unguard_memory(char* addr, size_t bytes);
   203   static char*  map_memory(int fd, const char* file_name, size_t file_offset,
   204                            char *addr, size_t bytes, bool read_only = false,
   205                            bool allow_exec = false);
   206   static char*  remap_memory(int fd, const char* file_name, size_t file_offset,
   207                              char *addr, size_t bytes, bool read_only,
   208                              bool allow_exec);
   209   static bool   unmap_memory(char *addr, size_t bytes);
   210   static void   free_memory(char *addr, size_t bytes);
   211   static void   realign_memory(char *addr, size_t bytes, size_t alignment_hint);
   213   // NUMA-specific interface
   214   static bool   numa_has_static_binding();
   215   static bool   numa_has_group_homing();
   216   static void   numa_make_local(char *addr, size_t bytes, int lgrp_hint);
   217   static void   numa_make_global(char *addr, size_t bytes);
   218   static size_t numa_get_groups_num();
   219   static size_t numa_get_leaf_groups(int *ids, size_t size);
   220   static bool   numa_topology_changed();
   221   static int    numa_get_group_id();
   223   // Page manipulation
   224   struct page_info {
   225     size_t size;
   226     int lgrp_id;
   227   };
   228   static bool   get_page_info(char *start, page_info* info);
   229   static char*  scan_pages(char *start, char* end, page_info* page_expected, page_info* page_found);
   231   static char*  non_memory_address_word();
   232   // reserve, commit and pin the entire memory region
   233   static char*  reserve_memory_special(size_t size);
   234   static bool   release_memory_special(char* addr, size_t bytes);
   235   static bool   large_page_init();
   236   static size_t large_page_size();
   237   static bool   can_commit_large_page_memory();
   238   static bool   can_execute_large_page_memory();
   240   // OS interface to polling page
   241   static address get_polling_page()             { return _polling_page; }
   242   static void    set_polling_page(address page) { _polling_page = page; }
   243   static bool    is_poll_address(address addr)  { return addr >= _polling_page && addr < (_polling_page + os::vm_page_size()); }
   244   static void    make_polling_page_unreadable();
   245   static void    make_polling_page_readable();
   247   // Routines used to serialize the thread state without using membars
   248   static void    serialize_thread_states();
   250   // Since we write to the serialize page from every thread, we
   251   // want stores to be on unique cache lines whenever possible
   252   // in order to minimize CPU cross talk.  We pre-compute the
   253   // amount to shift the thread* to make this offset unique to
   254   // each thread.
   255   static int     get_serialize_page_shift_count() {
   256     return SerializePageShiftCount;
   257   }
   259   static void     set_serialize_page_mask(uintptr_t mask) {
   260     _serialize_page_mask = mask;
   261   }
   263   static unsigned int  get_serialize_page_mask() {
   264     return _serialize_page_mask;
   265   }
   267   static void    set_memory_serialize_page(address page);
   269   static address get_memory_serialize_page() {
   270     return (address)_mem_serialize_page;
   271   }
   273   static inline void write_memory_serialize_page(JavaThread *thread) {
   274     uintptr_t page_offset = ((uintptr_t)thread >>
   275                             get_serialize_page_shift_count()) &
   276                             get_serialize_page_mask();
   277     *(volatile int32_t *)((uintptr_t)_mem_serialize_page+page_offset) = 1;
   278   }
   280   static bool    is_memory_serialize_page(JavaThread *thread, address addr) {
   281     address thr_addr;
   282     if (UseMembar) return false;
   283     // Calculate thread specific address
   284     if (thread == NULL) return false;
   285     // TODO-FIXME: some platforms mask off faulting addresses to the base pagesize.
   286     // Instead of using a test for equality we should probably use something
   287     // of the form:
   288     // return ((_mem_serialize_page ^ addr) & -pagesize) == 0
   289     //
   290     thr_addr  = (address)(((uintptr_t)thread >>
   291                 get_serialize_page_shift_count()) &
   292                 get_serialize_page_mask()) + (uintptr_t)_mem_serialize_page;
   293     return  (thr_addr == addr);
   294   }
   296   static void block_on_serialize_page_trap();
   298   // threads
   300   enum ThreadType {
   301     vm_thread,
   302     cgc_thread,        // Concurrent GC thread
   303     pgc_thread,        // Parallel GC thread
   304     java_thread,
   305     compiler_thread,
   306     watcher_thread
   307   };
   309   static bool create_thread(Thread* thread,
   310                             ThreadType thr_type,
   311                             size_t stack_size = 0);
   312   static bool create_main_thread(JavaThread* thread);
   313   static bool create_attached_thread(JavaThread* thread);
   314   static void pd_start_thread(Thread* thread);
   315   static void start_thread(Thread* thread);
   317   static void initialize_thread();
   318   static void free_thread(OSThread* osthread);
   320   // thread id on Linux/64bit is 64bit, on Windows and Solaris, it's 32bit
   321   static intx current_thread_id();
   322   static int current_process_id();
   323   // hpi::read for calls from non native state
   324   // For performance, hpi::read is only callable from _thread_in_native
   325   static size_t read(int fd, void *buf, unsigned int nBytes);
   326   static int sleep(Thread* thread, jlong ms, bool interruptable);
   327   static int naked_sleep();
   328   static void infinite_sleep(); // never returns, use with CAUTION
   329   static void yield();        // Yields to all threads with same priority
   330   enum YieldResult {
   331     YIELD_SWITCHED = 1,         // caller descheduled, other ready threads exist & ran
   332     YIELD_NONEREADY = 0,        // No other runnable/ready threads.
   333                                 // platform-specific yield return immediately
   334     YIELD_UNKNOWN = -1          // Unknown: platform doesn't support _SWITCHED or _NONEREADY
   335     // YIELD_SWITCHED and YIELD_NONREADY imply the platform supports a "strong"
   336     // yield that can be used in lieu of blocking.
   337   } ;
   338   static YieldResult NakedYield () ;
   339   static void yield_all(int attempts = 0); // Yields to all other threads including lower priority
   340   static void loop_breaker(int attempts);  // called from within tight loops to possibly influence time-sharing
   341   static OSReturn set_priority(Thread* thread, ThreadPriority priority);
   342   static OSReturn get_priority(const Thread* const thread, ThreadPriority& priority);
   344   static void interrupt(Thread* thread);
   345   static bool is_interrupted(Thread* thread, bool clear_interrupted);
   347   static int pd_self_suspend_thread(Thread* thread);
   349   static ExtendedPC fetch_frame_from_context(void* ucVoid, intptr_t** sp, intptr_t** fp);
   350   static frame      fetch_frame_from_context(void* ucVoid);
   352   static ExtendedPC get_thread_pc(Thread *thread);
   353   static void breakpoint();
   355   static address current_stack_pointer();
   356   static address current_stack_base();
   357   static size_t current_stack_size();
   359   static int message_box(const char* title, const char* message);
   360   static char* do_you_want_to_debug(const char* message);
   362   // run cmd in a separate process and return its exit code; or -1 on failures
   363   static int fork_and_exec(char *cmd);
   365   // Set file to send error reports.
   366   static void set_error_file(const char *logfile);
   368   // os::exit() is merged with vm_exit()
   369   // static void exit(int num);
   371   // Terminate the VM, but don't exit the process
   372   static void shutdown();
   374   // Terminate with an error.  Default is to generate a core file on platforms
   375   // that support such things.  This calls shutdown() and then aborts.
   376   static void abort(bool dump_core = true);
   378   // Die immediately, no exit hook, no abort hook, no cleanup.
   379   static void die();
   381   // Reading directories.
   382   static DIR*           opendir(const char* dirname);
   383   static int            readdir_buf_size(const char *path);
   384   static struct dirent* readdir(DIR* dirp, dirent* dbuf);
   385   static int            closedir(DIR* dirp);
   387   // Dynamic library extension
   388   static const char*    dll_file_extension();
   390   static const char*    get_temp_directory();
   391   static const char*    get_current_directory(char *buf, int buflen);
   393   // Builds a platform-specific full library path given a ld path and lib name
   394   static void           dll_build_name(char* buffer, size_t size,
   395                                        const char* pathname, const char* fname);
   397   // Symbol lookup, find nearest function name; basically it implements
   398   // dladdr() for all platforms. Name of the nearest function is copied
   399   // to buf. Distance from its base address is returned as offset.
   400   // If function name is not found, buf[0] is set to '\0' and offset is
   401   // set to -1.
   402   static bool dll_address_to_function_name(address addr, char* buf,
   403                                            int buflen, int* offset);
   405   // Locate DLL/DSO. On success, full path of the library is copied to
   406   // buf, and offset is set to be the distance between addr and the
   407   // library's base address. On failure, buf[0] is set to '\0' and
   408   // offset is set to -1.
   409   static bool dll_address_to_library_name(address addr, char* buf,
   410                                           int buflen, int* offset);
   412   // Find out whether the pc is in the static code for jvm.dll/libjvm.so.
   413   static bool address_is_in_vm(address addr);
   415   // Loads .dll/.so and
   416   // in case of error it checks if .dll/.so was built for the
   417   // same architecture as Hotspot is running on
   418   static void* dll_load(const char *name, char *ebuf, int ebuflen);
   420   // lookup symbol in a shared library
   421   static void* dll_lookup(void* handle, const char* name);
   423   // Print out system information; they are called by fatal error handler.
   424   // Output format may be different on different platforms.
   425   static void print_os_info(outputStream* st);
   426   static void print_cpu_info(outputStream* st);
   427   static void print_memory_info(outputStream* st);
   428   static void print_dll_info(outputStream* st);
   429   static void print_environment_variables(outputStream* st, const char** env_list, char* buffer, int len);
   430   static void print_context(outputStream* st, void* context);
   431   static void print_siginfo(outputStream* st, void* siginfo);
   432   static void print_signal_handlers(outputStream* st, char* buf, size_t buflen);
   433   static void print_date_and_time(outputStream* st);
   435   // The following two functions are used by fatal error handler to trace
   436   // native (C) frames. They are not part of frame.hpp/frame.cpp because
   437   // frame.hpp/cpp assume thread is JavaThread, and also because different
   438   // OS/compiler may have different convention or provide different API to
   439   // walk C frames.
   440   //
   441   // We don't attempt to become a debugger, so we only follow frames if that
   442   // does not require a lookup in the unwind table, which is part of the binary
   443   // file but may be unsafe to read after a fatal error. So on x86, we can
   444   // only walk stack if %ebp is used as frame pointer; on ia64, it's not
   445   // possible to walk C stack without having the unwind table.
   446   static bool is_first_C_frame(frame *fr);
   447   static frame get_sender_for_C_frame(frame *fr);
   449   // return current frame. pc() and sp() are set to NULL on failure.
   450   static frame      current_frame();
   452   static void print_hex_dump(outputStream* st, address start, address end, int unitsize);
   454   // returns a string to describe the exception/signal;
   455   // returns NULL if exception_code is not an OS exception/signal.
   456   static const char* exception_name(int exception_code, char* buf, size_t buflen);
   458   // Returns native Java library, loads if necessary
   459   static void*    native_java_library();
   461   // Fills in path to jvm.dll/libjvm.so (this info used to find hpi).
   462   static void     jvm_path(char *buf, jint buflen);
   464   // JNI names
   465   static void     print_jni_name_prefix_on(outputStream* st, int args_size);
   466   static void     print_jni_name_suffix_on(outputStream* st, int args_size);
   468   // File conventions
   469   static const char* file_separator();
   470   static const char* line_separator();
   471   static const char* path_separator();
   473   // Init os specific system properties values
   474   static void init_system_properties_values();
   476   // IO operations, non-JVM_ version.
   477   static int stat(const char* path, struct stat* sbuf);
   478   static bool dir_is_empty(const char* path);
   480   // IO operations on binary files
   481   static int create_binary_file(const char* path, bool rewrite_existing);
   482   static jlong current_file_offset(int fd);
   483   static jlong seek_to_file_offset(int fd, jlong offset);
   485   // Thread Local Storage
   486   static int   allocate_thread_local_storage();
   487   static void  thread_local_storage_at_put(int index, void* value);
   488   static void* thread_local_storage_at(int index);
   489   static void  free_thread_local_storage(int index);
   491   // General allocation (must be MT-safe)
   492   static void* malloc  (size_t size);
   493   static void* realloc (void *memblock, size_t size);
   494   static void  free    (void *memblock);
   495   static bool  check_heap(bool force = false);      // verify C heap integrity
   496   static char* strdup(const char *);  // Like strdup
   498 #ifndef PRODUCT
   499   static int  num_mallocs;            // # of calls to malloc/realloc
   500   static size_t  alloc_bytes;         // # of bytes allocated
   501   static int  num_frees;              // # of calls to free
   502 #endif
   504   // Printing 64 bit integers
   505   static const char* jlong_format_specifier();
   506   static const char* julong_format_specifier();
   508   // Support for signals (see JVM_RaiseSignal, JVM_RegisterSignal)
   509   static void  signal_init();
   510   static void  signal_init_pd();
   511   static void  signal_notify(int signal_number);
   512   static void* signal(int signal_number, void* handler);
   513   static void  signal_raise(int signal_number);
   514   static int   signal_wait();
   515   static int   signal_lookup();
   516   static void* user_handler();
   517   static void  terminate_signal_thread();
   518   static int   sigexitnum_pd();
   520   // random number generation
   521   static long random();                    // return 32bit pseudorandom number
   522   static void init_random(long initval);   // initialize random sequence
   524   // Structured OS Exception support
   525   static void os_exception_wrapper(java_call_t f, JavaValue* value, methodHandle* method, JavaCallArguments* args, Thread* thread);
   527   // JVMTI & JVM monitoring and management support
   528   // The thread_cpu_time() and current_thread_cpu_time() are only
   529   // supported if is_thread_cpu_time_supported() returns true.
   530   // They are not supported on Solaris T1.
   532   // Thread CPU Time - return the fast estimate on a platform
   533   // On Solaris - call gethrvtime (fast) - user time only
   534   // On Linux   - fast clock_gettime where available - user+sys
   535   //            - otherwise: very slow /proc fs - user+sys
   536   // On Windows - GetThreadTimes - user+sys
   537   static jlong current_thread_cpu_time();
   538   static jlong thread_cpu_time(Thread* t);
   540   // Thread CPU Time with user_sys_cpu_time parameter.
   541   //
   542   // If user_sys_cpu_time is true, user+sys time is returned.
   543   // Otherwise, only user time is returned
   544   static jlong current_thread_cpu_time(bool user_sys_cpu_time);
   545   static jlong thread_cpu_time(Thread* t, bool user_sys_cpu_time);
   547   // Return a bunch of info about the timers.
   548   // Note that the returned info for these two functions may be different
   549   // on some platforms
   550   static void current_thread_cpu_time_info(jvmtiTimerInfo *info_ptr);
   551   static void thread_cpu_time_info(jvmtiTimerInfo *info_ptr);
   553   static bool is_thread_cpu_time_supported();
   555   // System loadavg support.  Returns -1 if load average cannot be obtained.
   556   static int loadavg(double loadavg[], int nelem);
   558   // Hook for os specific jvm options that we don't want to abort on seeing
   559   static bool obsolete_option(const JavaVMOption *option);
   561   // Platform dependent stuff
   562   #include "incls/_os_pd.hpp.incl"
   564   // debugging support (mostly used by debug.cpp)
   565   static bool find(address pc) PRODUCT_RETURN0; // OS specific function to make sense out of an address
   567   static bool dont_yield();                     // when true, JVM_Yield() is nop
   568   static void print_statistics();
   570   // Thread priority helpers (implemented in OS-specific part)
   571   static OSReturn set_native_priority(Thread* thread, int native_prio);
   572   static OSReturn get_native_priority(const Thread* const thread, int* priority_ptr);
   573   static int java_to_os_priority[MaxPriority + 1];
   574   // Hint to the underlying OS that a task switch would not be good.
   575   // Void return because it's a hint and can fail.
   576   static void hint_no_preempt();
   578   // Used at creation if requested by the diagnostic flag PauseAtStartup.
   579   // Causes the VM to wait until an external stimulus has been applied
   580   // (for Unix, that stimulus is a signal, for Windows, an external
   581   // ResumeThread call)
   582   static void pause();
   584  protected:
   585   static long _rand_seed;                   // seed for random number generator
   586   static int _processor_count;              // number of processors
   588   static char* format_boot_path(const char* format_string,
   589                                 const char* home,
   590                                 int home_len,
   591                                 char fileSep,
   592                                 char pathSep);
   593   static bool set_boot_path(char fileSep, char pathSep);
   594 };
   596 // Note that "PAUSE" is almost always used with synchronization
   597 // so arguably we should provide Atomic::SpinPause() instead
   598 // of the global SpinPause() with C linkage.
   599 // It'd also be eligible for inlining on many platforms.
   601 extern "C" int SpinPause () ;
   602 extern "C" int SafeFetch32 (int * adr, int errValue) ;
   603 extern "C" intptr_t SafeFetchN (intptr_t * adr, intptr_t errValue) ;

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