os.hpp revision 656:6bdd6923ba16
1/* 2 * Copyright 1997-2009 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 */ 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 29typedef void (*dll_func)(...); 30 31class Thread; 32class JavaThread; 33class Event; 34class DLL; 35class FileHandle; 36template<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 41enum 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 50enum 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 60typedef void (*java_call_t)(JavaValue* value, methodHandle* method, JavaCallArguments* args, Thread* thread); 61 62class os: AllStatic { 63 private: 64 enum { page_sizes_max = 9 }; // Size of _page_sizes array (8 plus a sentinel) 65 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]; 71 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 } 76 77 public: 78 79 static void init(void); // Called before command line parsing 80 static jint init_2(void); // Called after command line parsing 81 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); 85 86 static bool getenv(const char* name, char* buffer, int len); 87 static bool have_special_privileges(); 88 89 static jlong javaTimeMillis(); 90 static jlong javaTimeNanos(); 91 static void javaTimeNanos_info(jvmtiTimerInfo *info_ptr); 92 static void run_periodic_checks(); 93 94 95 // Returns the elapsed time in seconds since the vm started. 96 static double elapsedTime(); 97 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); 103 104 // Interface to the performance counter 105 static jlong elapsed_counter(); 106 static jlong elapsed_frequency(); 107 108 // The "virtual time" of a thread is the amount of time a thread has 109 // actually run. The first function indicates whether the OS supports 110 // this functionality for the current thread, and if so: 111 // * the second enables vtime tracking (if that is required). 112 // * the third tells whether vtime is enabled. 113 // * the fourth returns the elapsed virtual time for the current 114 // thread. 115 static bool supports_vtime(); 116 static bool enable_vtime(); 117 static bool vtime_enabled(); 118 static double elapsedVTime(); 119 120 // Return current local time in a string (YYYY-MM-DD HH:MM:SS). 121 // It is MT safe, but not async-safe, as reading time zone 122 // information may require a lock on some platforms. 123 static char* local_time_string(char *buf, size_t buflen); 124 static struct tm* localtime_pd (const time_t* clock, struct tm* res); 125 // Fill in buffer with current local time as an ISO-8601 string. 126 // E.g., YYYY-MM-DDThh:mm:ss.mmm+zzzz. 127 // Returns buffer, or NULL if it failed. 128 static char* iso8601_time(char* buffer, size_t buffer_length); 129 130 // Interface for detecting multiprocessor system 131 static inline bool is_MP() { 132 assert(_processor_count > 0, "invalid processor count"); 133 return _processor_count > 1; 134 } 135 static julong available_memory(); 136 static julong physical_memory(); 137 static julong allocatable_physical_memory(julong size); 138 static bool is_server_class_machine(); 139 140 // number of CPUs 141 static int processor_count() { 142 return _processor_count; 143 } 144 145 // Returns the number of CPUs this process is currently allowed to run on. 146 // Note that on some OSes this can change dynamically. 147 static int active_processor_count(); 148 149 // Bind processes to processors. 150 // This is a two step procedure: 151 // first you generate a distribution of processes to processors, 152 // then you bind processes according to that distribution. 153 // Compute a distribution for number of processes to processors. 154 // Stores the processor id's into the distribution array argument. 155 // Returns true if it worked, false if it didn't. 156 static bool distribute_processes(uint length, uint* distribution); 157 // Binds the current process to a processor. 158 // Returns true if it worked, false if it didn't. 159 static bool bind_to_processor(uint processor_id); 160 161 // Interface for stack banging (predetect possible stack overflow for 162 // exception processing) There are guard pages, and above that shadow 163 // pages for stack overflow checking. 164 static bool uses_stack_guard_pages(); 165 static bool allocate_stack_guard_pages(); 166 static void bang_stack_shadow_pages(); 167 static bool stack_shadow_pages_available(Thread *thread, methodHandle method); 168 169 // OS interface to Virtual Memory 170 171 // Return the default page size. 172 static int vm_page_size(); 173 174 // Return the page size to use for a region of memory. The min_pages argument 175 // is a hint intended to limit fragmentation; it says the returned page size 176 // should be <= region_max_size / min_pages. Because min_pages is a hint, 177 // this routine may return a size larger than region_max_size / min_pages. 178 // 179 // The current implementation ignores min_pages if a larger page size is an 180 // exact multiple of both region_min_size and region_max_size. This allows 181 // larger pages to be used when doing so would not cause fragmentation; in 182 // particular, a single page can be used when region_min_size == 183 // region_max_size == a supported page size. 184 static size_t page_size_for_region(size_t region_min_size, 185 size_t region_max_size, 186 uint min_pages); 187 188 // Method for tracing page sizes returned by the above method; enabled by 189 // TracePageSizes. The region_{min,max}_size parameters should be the values 190 // passed to page_size_for_region() and page_size should be the result of that 191 // call. The (optional) base and size parameters should come from the 192 // ReservedSpace base() and size() methods. 193 static void trace_page_sizes(const char* str, const size_t region_min_size, 194 const size_t region_max_size, 195 const size_t page_size, 196 const char* base = NULL, 197 const size_t size = 0) PRODUCT_RETURN; 198 199 static int vm_allocation_granularity(); 200 static char* reserve_memory(size_t bytes, char* addr = 0, 201 size_t alignment_hint = 0); 202 static char* attempt_reserve_memory_at(size_t bytes, char* addr); 203 static void split_reserved_memory(char *base, size_t size, 204 size_t split, bool realloc); 205 static bool commit_memory(char* addr, size_t bytes, 206 bool executable = false); 207 static bool commit_memory(char* addr, size_t size, size_t alignment_hint, 208 bool executable = false); 209 static bool uncommit_memory(char* addr, size_t bytes); 210 static bool release_memory(char* addr, size_t bytes); 211 212 enum ProtType { MEM_PROT_NONE, MEM_PROT_READ, MEM_PROT_RW, MEM_PROT_RWX }; 213 static bool protect_memory(char* addr, size_t bytes, ProtType prot, 214 bool is_committed = true); 215 216 static bool guard_memory(char* addr, size_t bytes); 217 static bool unguard_memory(char* addr, size_t bytes); 218 static char* map_memory(int fd, const char* file_name, size_t file_offset, 219 char *addr, size_t bytes, bool read_only = false, 220 bool allow_exec = false); 221 static char* remap_memory(int fd, const char* file_name, size_t file_offset, 222 char *addr, size_t bytes, bool read_only, 223 bool allow_exec); 224 static bool unmap_memory(char *addr, size_t bytes); 225 static void free_memory(char *addr, size_t bytes); 226 static void realign_memory(char *addr, size_t bytes, size_t alignment_hint); 227 228 // NUMA-specific interface 229 static bool numa_has_static_binding(); 230 static bool numa_has_group_homing(); 231 static void numa_make_local(char *addr, size_t bytes, int lgrp_hint); 232 static void numa_make_global(char *addr, size_t bytes); 233 static size_t numa_get_groups_num(); 234 static size_t numa_get_leaf_groups(int *ids, size_t size); 235 static bool numa_topology_changed(); 236 static int numa_get_group_id(); 237 238 // Page manipulation 239 struct page_info { 240 size_t size; 241 int lgrp_id; 242 }; 243 static bool get_page_info(char *start, page_info* info); 244 static char* scan_pages(char *start, char* end, page_info* page_expected, page_info* page_found); 245 246 static char* non_memory_address_word(); 247 // reserve, commit and pin the entire memory region 248 static char* reserve_memory_special(size_t size, char* addr = NULL, 249 bool executable = false); 250 static bool release_memory_special(char* addr, size_t bytes); 251 static bool large_page_init(); 252 static size_t large_page_size(); 253 static bool can_commit_large_page_memory(); 254 static bool can_execute_large_page_memory(); 255 256 // OS interface to polling page 257 static address get_polling_page() { return _polling_page; } 258 static void set_polling_page(address page) { _polling_page = page; } 259 static bool is_poll_address(address addr) { return addr >= _polling_page && addr < (_polling_page + os::vm_page_size()); } 260 static void make_polling_page_unreadable(); 261 static void make_polling_page_readable(); 262 263 // Routines used to serialize the thread state without using membars 264 static void serialize_thread_states(); 265 266 // Since we write to the serialize page from every thread, we 267 // want stores to be on unique cache lines whenever possible 268 // in order to minimize CPU cross talk. We pre-compute the 269 // amount to shift the thread* to make this offset unique to 270 // each thread. 271 static int get_serialize_page_shift_count() { 272 return SerializePageShiftCount; 273 } 274 275 static void set_serialize_page_mask(uintptr_t mask) { 276 _serialize_page_mask = mask; 277 } 278 279 static unsigned int get_serialize_page_mask() { 280 return _serialize_page_mask; 281 } 282 283 static void set_memory_serialize_page(address page); 284 285 static address get_memory_serialize_page() { 286 return (address)_mem_serialize_page; 287 } 288 289 static inline void write_memory_serialize_page(JavaThread *thread) { 290 uintptr_t page_offset = ((uintptr_t)thread >> 291 get_serialize_page_shift_count()) & 292 get_serialize_page_mask(); 293 *(volatile int32_t *)((uintptr_t)_mem_serialize_page+page_offset) = 1; 294 } 295 296 static bool is_memory_serialize_page(JavaThread *thread, address addr) { 297 address thr_addr; 298 if (UseMembar) return false; 299 // Calculate thread specific address 300 if (thread == NULL) return false; 301 // TODO-FIXME: some platforms mask off faulting addresses to the base pagesize. 302 // Instead of using a test for equality we should probably use something 303 // of the form: 304 // return ((_mem_serialize_page ^ addr) & -pagesize) == 0 305 // 306 thr_addr = (address)(((uintptr_t)thread >> 307 get_serialize_page_shift_count()) & 308 get_serialize_page_mask()) + (uintptr_t)_mem_serialize_page; 309 return (thr_addr == addr); 310 } 311 312 static void block_on_serialize_page_trap(); 313 314 // threads 315 316 enum ThreadType { 317 vm_thread, 318 cgc_thread, // Concurrent GC thread 319 pgc_thread, // Parallel GC thread 320 java_thread, 321 compiler_thread, 322 watcher_thread 323 }; 324 325 static bool create_thread(Thread* thread, 326 ThreadType thr_type, 327 size_t stack_size = 0); 328 static bool create_main_thread(JavaThread* thread); 329 static bool create_attached_thread(JavaThread* thread); 330 static void pd_start_thread(Thread* thread); 331 static void start_thread(Thread* thread); 332 333 static void initialize_thread(); 334 static void free_thread(OSThread* osthread); 335 336 // thread id on Linux/64bit is 64bit, on Windows and Solaris, it's 32bit 337 static intx current_thread_id(); 338 static int current_process_id(); 339 // hpi::read for calls from non native state 340 // For performance, hpi::read is only callable from _thread_in_native 341 static size_t read(int fd, void *buf, unsigned int nBytes); 342 static int sleep(Thread* thread, jlong ms, bool interruptable); 343 static int naked_sleep(); 344 static void infinite_sleep(); // never returns, use with CAUTION 345 static void yield(); // Yields to all threads with same priority 346 enum YieldResult { 347 YIELD_SWITCHED = 1, // caller descheduled, other ready threads exist & ran 348 YIELD_NONEREADY = 0, // No other runnable/ready threads. 349 // platform-specific yield return immediately 350 YIELD_UNKNOWN = -1 // Unknown: platform doesn't support _SWITCHED or _NONEREADY 351 // YIELD_SWITCHED and YIELD_NONREADY imply the platform supports a "strong" 352 // yield that can be used in lieu of blocking. 353 } ; 354 static YieldResult NakedYield () ; 355 static void yield_all(int attempts = 0); // Yields to all other threads including lower priority 356 static void loop_breaker(int attempts); // called from within tight loops to possibly influence time-sharing 357 static OSReturn set_priority(Thread* thread, ThreadPriority priority); 358 static OSReturn get_priority(const Thread* const thread, ThreadPriority& priority); 359 360 static void interrupt(Thread* thread); 361 static bool is_interrupted(Thread* thread, bool clear_interrupted); 362 363 static int pd_self_suspend_thread(Thread* thread); 364 365 static ExtendedPC fetch_frame_from_context(void* ucVoid, intptr_t** sp, intptr_t** fp); 366 static frame fetch_frame_from_context(void* ucVoid); 367 368 static ExtendedPC get_thread_pc(Thread *thread); 369 static void breakpoint(); 370 371 static address current_stack_pointer(); 372 static address current_stack_base(); 373 static size_t current_stack_size(); 374 375 static int message_box(const char* title, const char* message); 376 static char* do_you_want_to_debug(const char* message); 377 378 // run cmd in a separate process and return its exit code; or -1 on failures 379 static int fork_and_exec(char *cmd); 380 381 // Set file to send error reports. 382 static void set_error_file(const char *logfile); 383 384 // os::exit() is merged with vm_exit() 385 // static void exit(int num); 386 387 // Terminate the VM, but don't exit the process 388 static void shutdown(); 389 390 // Terminate with an error. Default is to generate a core file on platforms 391 // that support such things. This calls shutdown() and then aborts. 392 static void abort(bool dump_core = true); 393 394 // Die immediately, no exit hook, no abort hook, no cleanup. 395 static void die(); 396 397 // Reading directories. 398 static DIR* opendir(const char* dirname); 399 static int readdir_buf_size(const char *path); 400 static struct dirent* readdir(DIR* dirp, dirent* dbuf); 401 static int closedir(DIR* dirp); 402 403 // Dynamic library extension 404 static const char* dll_file_extension(); 405 406 static const char* get_temp_directory(); 407 static const char* get_current_directory(char *buf, int buflen); 408 409 // Builds a platform-specific full library path given a ld path and lib name 410 static void dll_build_name(char* buffer, size_t size, 411 const char* pathname, const char* fname); 412 413 // Symbol lookup, find nearest function name; basically it implements 414 // dladdr() for all platforms. Name of the nearest function is copied 415 // to buf. Distance from its base address is returned as offset. 416 // If function name is not found, buf[0] is set to '\0' and offset is 417 // set to -1. 418 static bool dll_address_to_function_name(address addr, char* buf, 419 int buflen, int* offset); 420 421 // Locate DLL/DSO. On success, full path of the library is copied to 422 // buf, and offset is set to be the distance between addr and the 423 // library's base address. On failure, buf[0] is set to '\0' and 424 // offset is set to -1. 425 static bool dll_address_to_library_name(address addr, char* buf, 426 int buflen, int* offset); 427 428 // Find out whether the pc is in the static code for jvm.dll/libjvm.so. 429 static bool address_is_in_vm(address addr); 430 431 // Loads .dll/.so and 432 // in case of error it checks if .dll/.so was built for the 433 // same architecture as Hotspot is running on 434 static void* dll_load(const char *name, char *ebuf, int ebuflen); 435 436 // lookup symbol in a shared library 437 static void* dll_lookup(void* handle, const char* name); 438 439 // Print out system information; they are called by fatal error handler. 440 // Output format may be different on different platforms. 441 static void print_os_info(outputStream* st); 442 static void print_cpu_info(outputStream* st); 443 static void print_memory_info(outputStream* st); 444 static void print_dll_info(outputStream* st); 445 static void print_environment_variables(outputStream* st, const char** env_list, char* buffer, int len); 446 static void print_context(outputStream* st, void* context); 447 static void print_siginfo(outputStream* st, void* siginfo); 448 static void print_signal_handlers(outputStream* st, char* buf, size_t buflen); 449 static void print_date_and_time(outputStream* st); 450 451 // The following two functions are used by fatal error handler to trace 452 // native (C) frames. They are not part of frame.hpp/frame.cpp because 453 // frame.hpp/cpp assume thread is JavaThread, and also because different 454 // OS/compiler may have different convention or provide different API to 455 // walk C frames. 456 // 457 // We don't attempt to become a debugger, so we only follow frames if that 458 // does not require a lookup in the unwind table, which is part of the binary 459 // file but may be unsafe to read after a fatal error. So on x86, we can 460 // only walk stack if %ebp is used as frame pointer; on ia64, it's not 461 // possible to walk C stack without having the unwind table. 462 static bool is_first_C_frame(frame *fr); 463 static frame get_sender_for_C_frame(frame *fr); 464 465 // return current frame. pc() and sp() are set to NULL on failure. 466 static frame current_frame(); 467 468 static void print_hex_dump(outputStream* st, address start, address end, int unitsize); 469 470 // returns a string to describe the exception/signal; 471 // returns NULL if exception_code is not an OS exception/signal. 472 static const char* exception_name(int exception_code, char* buf, size_t buflen); 473 474 // Returns native Java library, loads if necessary 475 static void* native_java_library(); 476 477 // Fills in path to jvm.dll/libjvm.so (this info used to find hpi). 478 static void jvm_path(char *buf, jint buflen); 479 480 // JNI names 481 static void print_jni_name_prefix_on(outputStream* st, int args_size); 482 static void print_jni_name_suffix_on(outputStream* st, int args_size); 483 484 // File conventions 485 static const char* file_separator(); 486 static const char* line_separator(); 487 static const char* path_separator(); 488 489 // Init os specific system properties values 490 static void init_system_properties_values(); 491 492 // IO operations, non-JVM_ version. 493 static int stat(const char* path, struct stat* sbuf); 494 static bool dir_is_empty(const char* path); 495 496 // IO operations on binary files 497 static int create_binary_file(const char* path, bool rewrite_existing); 498 static jlong current_file_offset(int fd); 499 static jlong seek_to_file_offset(int fd, jlong offset); 500 501 // Thread Local Storage 502 static int allocate_thread_local_storage(); 503 static void thread_local_storage_at_put(int index, void* value); 504 static void* thread_local_storage_at(int index); 505 static void free_thread_local_storage(int index); 506 507 // General allocation (must be MT-safe) 508 static void* malloc (size_t size); 509 static void* realloc (void *memblock, size_t size); 510 static void free (void *memblock); 511 static bool check_heap(bool force = false); // verify C heap integrity 512 static char* strdup(const char *); // Like strdup 513 514#ifndef PRODUCT 515 static int num_mallocs; // # of calls to malloc/realloc 516 static size_t alloc_bytes; // # of bytes allocated 517 static int num_frees; // # of calls to free 518#endif 519 520 // Printing 64 bit integers 521 static const char* jlong_format_specifier(); 522 static const char* julong_format_specifier(); 523 524 // Support for signals (see JVM_RaiseSignal, JVM_RegisterSignal) 525 static void signal_init(); 526 static void signal_init_pd(); 527 static void signal_notify(int signal_number); 528 static void* signal(int signal_number, void* handler); 529 static void signal_raise(int signal_number); 530 static int signal_wait(); 531 static int signal_lookup(); 532 static void* user_handler(); 533 static void terminate_signal_thread(); 534 static int sigexitnum_pd(); 535 536 // random number generation 537 static long random(); // return 32bit pseudorandom number 538 static void init_random(long initval); // initialize random sequence 539 540 // Structured OS Exception support 541 static void os_exception_wrapper(java_call_t f, JavaValue* value, methodHandle* method, JavaCallArguments* args, Thread* thread); 542 543 // JVMTI & JVM monitoring and management support 544 // The thread_cpu_time() and current_thread_cpu_time() are only 545 // supported if is_thread_cpu_time_supported() returns true. 546 // They are not supported on Solaris T1. 547 548 // Thread CPU Time - return the fast estimate on a platform 549 // On Solaris - call gethrvtime (fast) - user time only 550 // On Linux - fast clock_gettime where available - user+sys 551 // - otherwise: very slow /proc fs - user+sys 552 // On Windows - GetThreadTimes - user+sys 553 static jlong current_thread_cpu_time(); 554 static jlong thread_cpu_time(Thread* t); 555 556 // Thread CPU Time with user_sys_cpu_time parameter. 557 // 558 // If user_sys_cpu_time is true, user+sys time is returned. 559 // Otherwise, only user time is returned 560 static jlong current_thread_cpu_time(bool user_sys_cpu_time); 561 static jlong thread_cpu_time(Thread* t, bool user_sys_cpu_time); 562 563 // Return a bunch of info about the timers. 564 // Note that the returned info for these two functions may be different 565 // on some platforms 566 static void current_thread_cpu_time_info(jvmtiTimerInfo *info_ptr); 567 static void thread_cpu_time_info(jvmtiTimerInfo *info_ptr); 568 569 static bool is_thread_cpu_time_supported(); 570 571 // System loadavg support. Returns -1 if load average cannot be obtained. 572 static int loadavg(double loadavg[], int nelem); 573 574 // Hook for os specific jvm options that we don't want to abort on seeing 575 static bool obsolete_option(const JavaVMOption *option); 576 577 // Platform dependent stuff 578 #include "incls/_os_pd.hpp.incl" 579 580 // debugging support (mostly used by debug.cpp) 581 static bool find(address pc) PRODUCT_RETURN0; // OS specific function to make sense out of an address 582 583 static bool dont_yield(); // when true, JVM_Yield() is nop 584 static void print_statistics(); 585 586 // Thread priority helpers (implemented in OS-specific part) 587 static OSReturn set_native_priority(Thread* thread, int native_prio); 588 static OSReturn get_native_priority(const Thread* const thread, int* priority_ptr); 589 static int java_to_os_priority[MaxPriority + 1]; 590 // Hint to the underlying OS that a task switch would not be good. 591 // Void return because it's a hint and can fail. 592 static void hint_no_preempt(); 593 594 // Used at creation if requested by the diagnostic flag PauseAtStartup. 595 // Causes the VM to wait until an external stimulus has been applied 596 // (for Unix, that stimulus is a signal, for Windows, an external 597 // ResumeThread call) 598 static void pause(); 599 600 protected: 601 static long _rand_seed; // seed for random number generator 602 static int _processor_count; // number of processors 603 604 static char* format_boot_path(const char* format_string, 605 const char* home, 606 int home_len, 607 char fileSep, 608 char pathSep); 609 static bool set_boot_path(char fileSep, char pathSep); 610}; 611 612// Note that "PAUSE" is almost always used with synchronization 613// so arguably we should provide Atomic::SpinPause() instead 614// of the global SpinPause() with C linkage. 615// It'd also be eligible for inlining on many platforms. 616 617extern "C" int SpinPause () ; 618extern "C" int SafeFetch32 (int * adr, int errValue) ; 619extern "C" intptr_t SafeFetchN (intptr_t * adr, intptr_t errValue) ; 620