1 /*
   2  * Copyright (c) 1997, 2010, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  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.
  28 
  29 typedef void (*dll_func)(...);
  30 
  31 class Thread;
  32 class JavaThread;
  33 class Event;
  34 class DLL;
  35 class FileHandle;
  36 template<class E> class GrowableArray;
  37 
  38 // %%%%% Moved ThreadState, START_FN, OSThread to new osThread.hpp. -- Rose
  39 
  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 };
  49 
  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 };
  58 
  59 // Typedef for structured exception handling support
  60 typedef void (*java_call_t)(JavaValue* value, methodHandle* method, JavaCallArguments* args, Thread* thread);
  61 
  62 class os: AllStatic {
  63  public:
  64   enum { page_sizes_max = 9 }; // Size of _page_sizes array (8 plus a sentinel)
  65 
  66  private:
  67   static OSThread*          _starting_thread;
  68   static address            _polling_page;
  69   static volatile int32_t * _mem_serialize_page;
  70   static uintptr_t          _serialize_page_mask;
  71  public:
  72   static size_t             _page_sizes[page_sizes_max];
  73 
  74  private:
  75   static void init_page_sizes(size_t default_page_size) {
  76     _page_sizes[0] = default_page_size;
  77     _page_sizes[1] = 0; // sentinel
  78   }
  79 
  80  public:
  81 
  82   static void init(void);                      // Called before command line parsing
  83   static jint init_2(void);                    // Called after command line parsing
  84   static void init_3(void);                    // Called at the end of vm init
  85 
  86   // File names are case-insensitive on windows only
  87   // Override me as needed
  88   static int    file_name_strcmp(const char* s1, const char* s2);
  89 
  90   static bool getenv(const char* name, char* buffer, int len);
  91   static bool have_special_privileges();
  92 
  93   static jlong  javaTimeMillis();
  94   static jlong  javaTimeNanos();
  95   static void   javaTimeNanos_info(jvmtiTimerInfo *info_ptr);
  96   static void   run_periodic_checks();
  97 
  98 
  99   // Returns the elapsed time in seconds since the vm started.
 100   static double elapsedTime();
 101 
 102   // Returns real time in seconds since an arbitrary point
 103   // in the past.
 104   static bool getTimesSecs(double* process_real_time,
 105                            double* process_user_time,
 106                            double* process_system_time);
 107 
 108   // Interface to the performance counter
 109   static jlong elapsed_counter();
 110   static jlong elapsed_frequency();
 111 
 112   // The "virtual time" of a thread is the amount of time a thread has
 113   // actually run.  The first function indicates whether the OS supports
 114   // this functionality for the current thread, and if so:
 115   //   * the second enables vtime tracking (if that is required).
 116   //   * the third tells whether vtime is enabled.
 117   //   * the fourth returns the elapsed virtual time for the current
 118   //     thread.
 119   static bool supports_vtime();
 120   static bool enable_vtime();
 121   static bool vtime_enabled();
 122   static double elapsedVTime();
 123 
 124   // Return current local time in a string (YYYY-MM-DD HH:MM:SS).
 125   // It is MT safe, but not async-safe, as reading time zone
 126   // information may require a lock on some platforms.
 127   static char*      local_time_string(char *buf, size_t buflen);
 128   static struct tm* localtime_pd     (const time_t* clock, struct tm*  res);
 129   // Fill in buffer with current local time as an ISO-8601 string.
 130   // E.g., YYYY-MM-DDThh:mm:ss.mmm+zzzz.
 131   // Returns buffer, or NULL if it failed.
 132   static char* iso8601_time(char* buffer, size_t buffer_length);
 133 
 134   // Interface for detecting multiprocessor system
 135   static inline bool is_MP() {
 136     assert(_processor_count > 0, "invalid processor count");
 137     return _processor_count > 1;
 138   }
 139   static julong available_memory();
 140   static julong physical_memory();
 141   static julong allocatable_physical_memory(julong size);
 142   static bool is_server_class_machine();
 143 
 144   // number of CPUs
 145   static int processor_count() {
 146     return _processor_count;
 147   }
 148   static void set_processor_count(int count) { _processor_count = count; }
 149 
 150   // Returns the number of CPUs this process is currently allowed to run on.
 151   // Note that on some OSes this can change dynamically.
 152   static int active_processor_count();
 153 
 154   // Bind processes to processors.
 155   //     This is a two step procedure:
 156   //     first you generate a distribution of processes to processors,
 157   //     then you bind processes according to that distribution.
 158   // Compute a distribution for number of processes to processors.
 159   //    Stores the processor id's into the distribution array argument.
 160   //    Returns true if it worked, false if it didn't.
 161   static bool distribute_processes(uint length, uint* distribution);
 162   // Binds the current process to a processor.
 163   //    Returns true if it worked, false if it didn't.
 164   static bool bind_to_processor(uint processor_id);
 165 
 166   // Interface for stack banging (predetect possible stack overflow for
 167   // exception processing)  There are guard pages, and above that shadow
 168   // pages for stack overflow checking.
 169   static bool uses_stack_guard_pages();
 170   static bool allocate_stack_guard_pages();
 171   static void bang_stack_shadow_pages();
 172   static bool stack_shadow_pages_available(Thread *thread, methodHandle method);
 173 
 174   // OS interface to Virtual Memory
 175 
 176   // Return the default page size.
 177   static int    vm_page_size();
 178 
 179   // Return the page size to use for a region of memory.  The min_pages argument
 180   // is a hint intended to limit fragmentation; it says the returned page size
 181   // should be <= region_max_size / min_pages.  Because min_pages is a hint,
 182   // this routine may return a size larger than region_max_size / min_pages.
 183   //
 184   // The current implementation ignores min_pages if a larger page size is an
 185   // exact multiple of both region_min_size and region_max_size.  This allows
 186   // larger pages to be used when doing so would not cause fragmentation; in
 187   // particular, a single page can be used when region_min_size ==
 188   // region_max_size == a supported page size.
 189   static size_t page_size_for_region(size_t region_min_size,
 190                                      size_t region_max_size,
 191                                      uint min_pages);
 192 
 193   // Method for tracing page sizes returned by the above method; enabled by
 194   // TracePageSizes.  The region_{min,max}_size parameters should be the values
 195   // passed to page_size_for_region() and page_size should be the result of that
 196   // call.  The (optional) base and size parameters should come from the
 197   // ReservedSpace base() and size() methods.
 198   static void trace_page_sizes(const char* str, const size_t region_min_size,
 199                                const size_t region_max_size,
 200                                const size_t page_size,
 201                                const char* base = NULL,
 202                                const size_t size = 0) PRODUCT_RETURN;
 203 
 204   static int    vm_allocation_granularity();
 205   static char*  reserve_memory(size_t bytes, char* addr = 0,
 206                                size_t alignment_hint = 0);
 207   static char*  attempt_reserve_memory_at(size_t bytes, char* addr);
 208   static void   split_reserved_memory(char *base, size_t size,
 209                                       size_t split, bool realloc);
 210   static bool   commit_memory(char* addr, size_t bytes,
 211                               bool executable = false);
 212   static bool   commit_memory(char* addr, size_t size, size_t alignment_hint,
 213                               bool executable = false);
 214   static bool   uncommit_memory(char* addr, size_t bytes);
 215   static bool   release_memory(char* addr, size_t bytes);
 216 
 217   enum ProtType { MEM_PROT_NONE, MEM_PROT_READ, MEM_PROT_RW, MEM_PROT_RWX };
 218   static bool   protect_memory(char* addr, size_t bytes, ProtType prot,
 219                                bool is_committed = true);
 220 
 221   static bool   guard_memory(char* addr, size_t bytes);
 222   static bool   unguard_memory(char* addr, size_t bytes);
 223   static bool   create_stack_guard_pages(char* addr, size_t bytes);
 224   static bool   remove_stack_guard_pages(char* addr, size_t bytes);
 225 
 226   static char*  map_memory(int fd, const char* file_name, size_t file_offset,
 227                            char *addr, size_t bytes, bool read_only = false,
 228                            bool allow_exec = false);
 229   static char*  remap_memory(int fd, const char* file_name, size_t file_offset,
 230                              char *addr, size_t bytes, bool read_only,
 231                              bool allow_exec);
 232   static bool   unmap_memory(char *addr, size_t bytes);
 233   static void   free_memory(char *addr, size_t bytes);
 234   static void   realign_memory(char *addr, size_t bytes, size_t alignment_hint);
 235 
 236   // NUMA-specific interface
 237   static bool   numa_has_static_binding();
 238   static bool   numa_has_group_homing();
 239   static void   numa_make_local(char *addr, size_t bytes, int lgrp_hint);
 240   static void   numa_make_global(char *addr, size_t bytes);
 241   static size_t numa_get_groups_num();
 242   static size_t numa_get_leaf_groups(int *ids, size_t size);
 243   static bool   numa_topology_changed();
 244   static int    numa_get_group_id();
 245 
 246   // Page manipulation
 247   struct page_info {
 248     size_t size;
 249     int lgrp_id;
 250   };
 251   static bool   get_page_info(char *start, page_info* info);
 252   static char*  scan_pages(char *start, char* end, page_info* page_expected, page_info* page_found);
 253 
 254   static char*  non_memory_address_word();
 255   // reserve, commit and pin the entire memory region
 256   static char*  reserve_memory_special(size_t size, char* addr = NULL,
 257                 bool executable = false);
 258   static bool   release_memory_special(char* addr, size_t bytes);
 259   static bool   large_page_init();
 260   static size_t large_page_size();
 261   static bool   can_commit_large_page_memory();
 262   static bool   can_execute_large_page_memory();
 263 
 264   // OS interface to polling page
 265   static address get_polling_page()             { return _polling_page; }
 266   static void    set_polling_page(address page) { _polling_page = page; }
 267   static bool    is_poll_address(address addr)  { return addr >= _polling_page && addr < (_polling_page + os::vm_page_size()); }
 268   static void    make_polling_page_unreadable();
 269   static void    make_polling_page_readable();
 270 
 271   // Routines used to serialize the thread state without using membars
 272   static void    serialize_thread_states();
 273 
 274   // Since we write to the serialize page from every thread, we
 275   // want stores to be on unique cache lines whenever possible
 276   // in order to minimize CPU cross talk.  We pre-compute the
 277   // amount to shift the thread* to make this offset unique to
 278   // each thread.
 279   static int     get_serialize_page_shift_count() {
 280     return SerializePageShiftCount;
 281   }
 282 
 283   static void     set_serialize_page_mask(uintptr_t mask) {
 284     _serialize_page_mask = mask;
 285   }
 286 
 287   static unsigned int  get_serialize_page_mask() {
 288     return _serialize_page_mask;
 289   }
 290 
 291   static void    set_memory_serialize_page(address page);
 292 
 293   static address get_memory_serialize_page() {
 294     return (address)_mem_serialize_page;
 295   }
 296 
 297   static inline void write_memory_serialize_page(JavaThread *thread) {
 298     uintptr_t page_offset = ((uintptr_t)thread >>
 299                             get_serialize_page_shift_count()) &
 300                             get_serialize_page_mask();
 301     *(volatile int32_t *)((uintptr_t)_mem_serialize_page+page_offset) = 1;
 302   }
 303 
 304   static bool    is_memory_serialize_page(JavaThread *thread, address addr) {
 305     if (UseMembar) return false;
 306     // Previously this function calculated the exact address of this
 307     // thread's serialize page, and checked if the faulting address
 308     // was equal.  However, some platforms mask off faulting addresses
 309     // to the page size, so now we just check that the address is
 310     // within the page.  This makes the thread argument unnecessary,
 311     // but we retain the NULL check to preserve existing behaviour.
 312     if (thread == NULL) return false;
 313     address page = (address) _mem_serialize_page;
 314     return addr >= page && addr < (page + os::vm_page_size());
 315   }
 316 
 317   static void block_on_serialize_page_trap();
 318 
 319   // threads
 320 
 321   enum ThreadType {
 322     vm_thread,
 323     cgc_thread,        // Concurrent GC thread
 324     pgc_thread,        // Parallel GC thread
 325     java_thread,
 326     compiler_thread,
 327     watcher_thread,
 328     os_thread
 329   };
 330 
 331   static bool create_thread(Thread* thread,
 332                             ThreadType thr_type,
 333                             size_t stack_size = 0);
 334   static bool create_main_thread(JavaThread* thread);
 335   static bool create_attached_thread(JavaThread* thread);
 336   static void pd_start_thread(Thread* thread);
 337   static void start_thread(Thread* thread);
 338 
 339   static void initialize_thread();
 340   static void free_thread(OSThread* osthread);
 341 
 342   // thread id on Linux/64bit is 64bit, on Windows and Solaris, it's 32bit
 343   static intx current_thread_id();
 344   static int current_process_id();
 345   // hpi::read for calls from non native state
 346   // For performance, hpi::read is only callable from _thread_in_native
 347   static size_t read(int fd, void *buf, unsigned int nBytes);
 348   static int sleep(Thread* thread, jlong ms, bool interruptable);
 349   static int naked_sleep();
 350   static void infinite_sleep(); // never returns, use with CAUTION
 351   static void yield();        // Yields to all threads with same priority
 352   enum YieldResult {
 353     YIELD_SWITCHED = 1,         // caller descheduled, other ready threads exist & ran
 354     YIELD_NONEREADY = 0,        // No other runnable/ready threads.
 355                                 // platform-specific yield return immediately
 356     YIELD_UNKNOWN = -1          // Unknown: platform doesn't support _SWITCHED or _NONEREADY
 357     // YIELD_SWITCHED and YIELD_NONREADY imply the platform supports a "strong"
 358     // yield that can be used in lieu of blocking.
 359   } ;
 360   static YieldResult NakedYield () ;
 361   static void yield_all(int attempts = 0); // Yields to all other threads including lower priority
 362   static void loop_breaker(int attempts);  // called from within tight loops to possibly influence time-sharing
 363   static OSReturn set_priority(Thread* thread, ThreadPriority priority);
 364   static OSReturn get_priority(const Thread* const thread, ThreadPriority& priority);
 365 
 366   static void interrupt(Thread* thread);
 367   static bool is_interrupted(Thread* thread, bool clear_interrupted);
 368 
 369   static int pd_self_suspend_thread(Thread* thread);
 370 
 371   static ExtendedPC fetch_frame_from_context(void* ucVoid, intptr_t** sp, intptr_t** fp);
 372   static frame      fetch_frame_from_context(void* ucVoid);
 373 
 374   static ExtendedPC get_thread_pc(Thread *thread);
 375   static void breakpoint();
 376 
 377   static address current_stack_pointer();
 378   static address current_stack_base();
 379   static size_t current_stack_size();
 380 
 381   static int message_box(const char* title, const char* message);
 382   static char* do_you_want_to_debug(const char* message);
 383 
 384   // run cmd in a separate process and return its exit code; or -1 on failures
 385   static int fork_and_exec(char *cmd);
 386 
 387   // Set file to send error reports.
 388   static void set_error_file(const char *logfile);
 389 
 390   // os::exit() is merged with vm_exit()
 391   // static void exit(int num);
 392 
 393   // Terminate the VM, but don't exit the process
 394   static void shutdown();
 395 
 396   // Terminate with an error.  Default is to generate a core file on platforms
 397   // that support such things.  This calls shutdown() and then aborts.
 398   static void abort(bool dump_core = true);
 399 
 400   // Die immediately, no exit hook, no abort hook, no cleanup.
 401   static void die();
 402 
 403   // Reading directories.
 404   static DIR*           opendir(const char* dirname);
 405   static int            readdir_buf_size(const char *path);
 406   static struct dirent* readdir(DIR* dirp, dirent* dbuf);
 407   static int            closedir(DIR* dirp);
 408 
 409   // Dynamic library extension
 410   static const char*    dll_file_extension();
 411 
 412   static const char*    get_temp_directory();
 413   static const char*    get_current_directory(char *buf, int buflen);
 414 
 415   // Builds a platform-specific full library path given a ld path and lib name
 416   static void           dll_build_name(char* buffer, size_t size,
 417                                        const char* pathname, const char* fname);
 418 
 419   // Symbol lookup, find nearest function name; basically it implements
 420   // dladdr() for all platforms. Name of the nearest function is copied
 421   // to buf. Distance from its base address is returned as offset.
 422   // If function name is not found, buf[0] is set to '\0' and offset is
 423   // set to -1.
 424   static bool dll_address_to_function_name(address addr, char* buf,
 425                                            int buflen, int* offset);
 426 
 427   // Locate DLL/DSO. On success, full path of the library is copied to
 428   // buf, and offset is set to be the distance between addr and the
 429   // library's base address. On failure, buf[0] is set to '\0' and
 430   // offset is set to -1.
 431   static bool dll_address_to_library_name(address addr, char* buf,
 432                                           int buflen, int* offset);
 433 
 434   // Find out whether the pc is in the static code for jvm.dll/libjvm.so.
 435   static bool address_is_in_vm(address addr);
 436 
 437   // Loads .dll/.so and
 438   // in case of error it checks if .dll/.so was built for the
 439   // same architecture as Hotspot is running on
 440   static void* dll_load(const char *name, char *ebuf, int ebuflen);
 441 
 442   // lookup symbol in a shared library
 443   static void* dll_lookup(void* handle, const char* name);
 444 
 445   // Print out system information; they are called by fatal error handler.
 446   // Output format may be different on different platforms.
 447   static void print_os_info(outputStream* st);
 448   static void print_cpu_info(outputStream* st);
 449   static void print_memory_info(outputStream* st);
 450   static void print_dll_info(outputStream* st);
 451   static void print_environment_variables(outputStream* st, const char** env_list, char* buffer, int len);
 452   static void print_context(outputStream* st, void* context);
 453   static void print_register_info(outputStream* st, void* context);
 454   static void print_siginfo(outputStream* st, void* siginfo);
 455   static void print_signal_handlers(outputStream* st, char* buf, size_t buflen);
 456   static void print_date_and_time(outputStream* st);
 457 
 458   static void print_location(outputStream* st, intptr_t x, bool verbose = false);
 459 
 460   // The following two functions are used by fatal error handler to trace
 461   // native (C) frames. They are not part of frame.hpp/frame.cpp because
 462   // frame.hpp/cpp assume thread is JavaThread, and also because different
 463   // OS/compiler may have different convention or provide different API to
 464   // walk C frames.
 465   //
 466   // We don't attempt to become a debugger, so we only follow frames if that
 467   // does not require a lookup in the unwind table, which is part of the binary
 468   // file but may be unsafe to read after a fatal error. So on x86, we can
 469   // only walk stack if %ebp is used as frame pointer; on ia64, it's not
 470   // possible to walk C stack without having the unwind table.
 471   static bool is_first_C_frame(frame *fr);
 472   static frame get_sender_for_C_frame(frame *fr);
 473 
 474   // return current frame. pc() and sp() are set to NULL on failure.
 475   static frame      current_frame();
 476 
 477   static void print_hex_dump(outputStream* st, address start, address end, int unitsize);
 478 
 479   // returns a string to describe the exception/signal;
 480   // returns NULL if exception_code is not an OS exception/signal.
 481   static const char* exception_name(int exception_code, char* buf, size_t buflen);
 482 
 483   // Returns native Java library, loads if necessary
 484   static void*    native_java_library();
 485 
 486   // Fills in path to jvm.dll/libjvm.so (this info used to find hpi).
 487   static void     jvm_path(char *buf, jint buflen);
 488 
 489   // Returns true if we are running in a headless jre.
 490   static bool     is_headless_jre();
 491 
 492   // JNI names
 493   static void     print_jni_name_prefix_on(outputStream* st, int args_size);
 494   static void     print_jni_name_suffix_on(outputStream* st, int args_size);
 495 
 496   // File conventions
 497   static const char* file_separator();
 498   static const char* line_separator();
 499   static const char* path_separator();
 500 
 501   // Init os specific system properties values
 502   static void init_system_properties_values();
 503 
 504   // IO operations, non-JVM_ version.
 505   static int stat(const char* path, struct stat* sbuf);
 506   static bool dir_is_empty(const char* path);
 507 
 508   // IO operations on binary files
 509   static int create_binary_file(const char* path, bool rewrite_existing);
 510   static jlong current_file_offset(int fd);
 511   static jlong seek_to_file_offset(int fd, jlong offset);
 512 
 513   // Thread Local Storage
 514   static int   allocate_thread_local_storage();
 515   static void  thread_local_storage_at_put(int index, void* value);
 516   static void* thread_local_storage_at(int index);
 517   static void  free_thread_local_storage(int index);
 518 
 519   // General allocation (must be MT-safe)
 520   static void* malloc  (size_t size);
 521   static void* realloc (void *memblock, size_t size);
 522   static void  free    (void *memblock);
 523   static bool  check_heap(bool force = false);      // verify C heap integrity
 524   static char* strdup(const char *);  // Like strdup
 525 
 526 #ifndef PRODUCT
 527   static int  num_mallocs;            // # of calls to malloc/realloc
 528   static size_t  alloc_bytes;         // # of bytes allocated
 529   static int  num_frees;              // # of calls to free
 530 #endif
 531 
 532   // Printing 64 bit integers
 533   static const char* jlong_format_specifier();
 534   static const char* julong_format_specifier();
 535 
 536   // Support for signals (see JVM_RaiseSignal, JVM_RegisterSignal)
 537   static void  signal_init();
 538   static void  signal_init_pd();
 539   static void  signal_notify(int signal_number);
 540   static void* signal(int signal_number, void* handler);
 541   static void  signal_raise(int signal_number);
 542   static int   signal_wait();
 543   static int   signal_lookup();
 544   static void* user_handler();
 545   static void  terminate_signal_thread();
 546   static int   sigexitnum_pd();
 547 
 548   // random number generation
 549   static long random();                    // return 32bit pseudorandom number
 550   static void init_random(long initval);   // initialize random sequence
 551 
 552   // Structured OS Exception support
 553   static void os_exception_wrapper(java_call_t f, JavaValue* value, methodHandle* method, JavaCallArguments* args, Thread* thread);
 554 
 555   // JVMTI & JVM monitoring and management support
 556   // The thread_cpu_time() and current_thread_cpu_time() are only
 557   // supported if is_thread_cpu_time_supported() returns true.
 558   // They are not supported on Solaris T1.
 559 
 560   // Thread CPU Time - return the fast estimate on a platform
 561   // On Solaris - call gethrvtime (fast) - user time only
 562   // On Linux   - fast clock_gettime where available - user+sys
 563   //            - otherwise: very slow /proc fs - user+sys
 564   // On Windows - GetThreadTimes - user+sys
 565   static jlong current_thread_cpu_time();
 566   static jlong thread_cpu_time(Thread* t);
 567 
 568   // Thread CPU Time with user_sys_cpu_time parameter.
 569   //
 570   // If user_sys_cpu_time is true, user+sys time is returned.
 571   // Otherwise, only user time is returned
 572   static jlong current_thread_cpu_time(bool user_sys_cpu_time);
 573   static jlong thread_cpu_time(Thread* t, bool user_sys_cpu_time);
 574 
 575   // Return a bunch of info about the timers.
 576   // Note that the returned info for these two functions may be different
 577   // on some platforms
 578   static void current_thread_cpu_time_info(jvmtiTimerInfo *info_ptr);
 579   static void thread_cpu_time_info(jvmtiTimerInfo *info_ptr);
 580 
 581   static bool is_thread_cpu_time_supported();
 582 
 583   // System loadavg support.  Returns -1 if load average cannot be obtained.
 584   static int loadavg(double loadavg[], int nelem);
 585 
 586   // Hook for os specific jvm options that we don't want to abort on seeing
 587   static bool obsolete_option(const JavaVMOption *option);
 588 
 589   // Platform dependent stuff
 590   #include "incls/_os_pd.hpp.incl"
 591 
 592   // debugging support (mostly used by debug.cpp but also fatal error handler)
 593   static bool find(address pc, outputStream* st = tty); // OS specific function to make sense out of an address
 594 
 595   static bool dont_yield();                     // when true, JVM_Yield() is nop
 596   static void print_statistics();
 597 
 598   // Thread priority helpers (implemented in OS-specific part)
 599   static OSReturn set_native_priority(Thread* thread, int native_prio);
 600   static OSReturn get_native_priority(const Thread* const thread, int* priority_ptr);
 601   static int java_to_os_priority[MaxPriority + 1];
 602   // Hint to the underlying OS that a task switch would not be good.
 603   // Void return because it's a hint and can fail.
 604   static void hint_no_preempt();
 605 
 606   // Used at creation if requested by the diagnostic flag PauseAtStartup.
 607   // Causes the VM to wait until an external stimulus has been applied
 608   // (for Unix, that stimulus is a signal, for Windows, an external
 609   // ResumeThread call)
 610   static void pause();
 611 
 612  protected:
 613   static long _rand_seed;                   // seed for random number generator
 614   static int _processor_count;              // number of processors
 615 
 616   static char* format_boot_path(const char* format_string,
 617                                 const char* home,
 618                                 int home_len,
 619                                 char fileSep,
 620                                 char pathSep);
 621   static bool set_boot_path(char fileSep, char pathSep);
 622   static char** split_path(const char* path, int* n);
 623 };
 624 
 625 // Note that "PAUSE" is almost always used with synchronization
 626 // so arguably we should provide Atomic::SpinPause() instead
 627 // of the global SpinPause() with C linkage.
 628 // It'd also be eligible for inlining on many platforms.
 629 
 630 extern "C" int SpinPause () ;
 631 extern "C" int SafeFetch32 (int * adr, int errValue) ;
 632 extern "C" intptr_t SafeFetchN (intptr_t * adr, intptr_t errValue) ;