Fri, 22 Oct 2010 15:59:34 -0400
6988353: refactor contended sync subsystem
Summary: reduce complexity by factoring synchronizer.cpp
Reviewed-by: dholmes, never, coleenp
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 */
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 public:
64 enum { page_sizes_max = 9 }; // Size of _page_sizes array (8 plus a sentinel)
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];
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 }
80 public:
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
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);
90 static bool getenv(const char* name, char* buffer, int len);
91 static bool have_special_privileges();
93 static jlong javaTimeMillis();
94 static jlong javaTimeNanos();
95 static void javaTimeNanos_info(jvmtiTimerInfo *info_ptr);
96 static void run_periodic_checks();
99 // Returns the elapsed time in seconds since the vm started.
100 static double elapsedTime();
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);
108 // Interface to the performance counter
109 static jlong elapsed_counter();
110 static jlong elapsed_frequency();
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();
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);
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();
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; }
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();
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);
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);
174 // OS interface to Virtual Memory
176 // Return the default page size.
177 static int vm_page_size();
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);
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;
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);
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);
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);
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);
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();
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);
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();
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();
271 // Routines used to serialize the thread state without using membars
272 static void serialize_thread_states();
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 }
283 static void set_serialize_page_mask(uintptr_t mask) {
284 _serialize_page_mask = mask;
285 }
287 static unsigned int get_serialize_page_mask() {
288 return _serialize_page_mask;
289 }
291 static void set_memory_serialize_page(address page);
293 static address get_memory_serialize_page() {
294 return (address)_mem_serialize_page;
295 }
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 }
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 }
317 static void block_on_serialize_page_trap();
319 // threads
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 };
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);
339 static void initialize_thread();
340 static void free_thread(OSThread* osthread);
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);
366 static void interrupt(Thread* thread);
367 static bool is_interrupted(Thread* thread, bool clear_interrupted);
369 static int pd_self_suspend_thread(Thread* thread);
371 static ExtendedPC fetch_frame_from_context(void* ucVoid, intptr_t** sp, intptr_t** fp);
372 static frame fetch_frame_from_context(void* ucVoid);
374 static ExtendedPC get_thread_pc(Thread *thread);
375 static void breakpoint();
377 static address current_stack_pointer();
378 static address current_stack_base();
379 static size_t current_stack_size();
381 static int message_box(const char* title, const char* message);
382 static char* do_you_want_to_debug(const char* message);
384 // run cmd in a separate process and return its exit code; or -1 on failures
385 static int fork_and_exec(char *cmd);
387 // Set file to send error reports.
388 static void set_error_file(const char *logfile);
390 // os::exit() is merged with vm_exit()
391 // static void exit(int num);
393 // Terminate the VM, but don't exit the process
394 static void shutdown();
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);
400 // Die immediately, no exit hook, no abort hook, no cleanup.
401 static void die();
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);
409 // Dynamic library extension
410 static const char* dll_file_extension();
412 static const char* get_temp_directory();
413 static const char* get_current_directory(char *buf, int buflen);
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);
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);
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);
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);
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);
442 // lookup symbol in a shared library
443 static void* dll_lookup(void* handle, const char* name);
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_siginfo(outputStream* st, void* siginfo);
454 static void print_signal_handlers(outputStream* st, char* buf, size_t buflen);
455 static void print_date_and_time(outputStream* st);
457 static void print_location(outputStream* st, intptr_t x, bool print_pc = false);
459 // The following two functions are used by fatal error handler to trace
460 // native (C) frames. They are not part of frame.hpp/frame.cpp because
461 // frame.hpp/cpp assume thread is JavaThread, and also because different
462 // OS/compiler may have different convention or provide different API to
463 // walk C frames.
464 //
465 // We don't attempt to become a debugger, so we only follow frames if that
466 // does not require a lookup in the unwind table, which is part of the binary
467 // file but may be unsafe to read after a fatal error. So on x86, we can
468 // only walk stack if %ebp is used as frame pointer; on ia64, it's not
469 // possible to walk C stack without having the unwind table.
470 static bool is_first_C_frame(frame *fr);
471 static frame get_sender_for_C_frame(frame *fr);
473 // return current frame. pc() and sp() are set to NULL on failure.
474 static frame current_frame();
476 static void print_hex_dump(outputStream* st, address start, address end, int unitsize);
478 // returns a string to describe the exception/signal;
479 // returns NULL if exception_code is not an OS exception/signal.
480 static const char* exception_name(int exception_code, char* buf, size_t buflen);
482 // Returns native Java library, loads if necessary
483 static void* native_java_library();
485 // Fills in path to jvm.dll/libjvm.so (this info used to find hpi).
486 static void jvm_path(char *buf, jint buflen);
488 // Returns true if we are running in a headless jre.
489 static bool is_headless_jre();
491 // JNI names
492 static void print_jni_name_prefix_on(outputStream* st, int args_size);
493 static void print_jni_name_suffix_on(outputStream* st, int args_size);
495 // File conventions
496 static const char* file_separator();
497 static const char* line_separator();
498 static const char* path_separator();
500 // Init os specific system properties values
501 static void init_system_properties_values();
503 // IO operations, non-JVM_ version.
504 static int stat(const char* path, struct stat* sbuf);
505 static bool dir_is_empty(const char* path);
507 // IO operations on binary files
508 static int create_binary_file(const char* path, bool rewrite_existing);
509 static jlong current_file_offset(int fd);
510 static jlong seek_to_file_offset(int fd, jlong offset);
512 // Thread Local Storage
513 static int allocate_thread_local_storage();
514 static void thread_local_storage_at_put(int index, void* value);
515 static void* thread_local_storage_at(int index);
516 static void free_thread_local_storage(int index);
518 // General allocation (must be MT-safe)
519 static void* malloc (size_t size);
520 static void* realloc (void *memblock, size_t size);
521 static void free (void *memblock);
522 static bool check_heap(bool force = false); // verify C heap integrity
523 static char* strdup(const char *); // Like strdup
525 #ifndef PRODUCT
526 static int num_mallocs; // # of calls to malloc/realloc
527 static size_t alloc_bytes; // # of bytes allocated
528 static int num_frees; // # of calls to free
529 #endif
531 // Printing 64 bit integers
532 static const char* jlong_format_specifier();
533 static const char* julong_format_specifier();
535 // Support for signals (see JVM_RaiseSignal, JVM_RegisterSignal)
536 static void signal_init();
537 static void signal_init_pd();
538 static void signal_notify(int signal_number);
539 static void* signal(int signal_number, void* handler);
540 static void signal_raise(int signal_number);
541 static int signal_wait();
542 static int signal_lookup();
543 static void* user_handler();
544 static void terminate_signal_thread();
545 static int sigexitnum_pd();
547 // random number generation
548 static long random(); // return 32bit pseudorandom number
549 static void init_random(long initval); // initialize random sequence
551 // Structured OS Exception support
552 static void os_exception_wrapper(java_call_t f, JavaValue* value, methodHandle* method, JavaCallArguments* args, Thread* thread);
554 // JVMTI & JVM monitoring and management support
555 // The thread_cpu_time() and current_thread_cpu_time() are only
556 // supported if is_thread_cpu_time_supported() returns true.
557 // They are not supported on Solaris T1.
559 // Thread CPU Time - return the fast estimate on a platform
560 // On Solaris - call gethrvtime (fast) - user time only
561 // On Linux - fast clock_gettime where available - user+sys
562 // - otherwise: very slow /proc fs - user+sys
563 // On Windows - GetThreadTimes - user+sys
564 static jlong current_thread_cpu_time();
565 static jlong thread_cpu_time(Thread* t);
567 // Thread CPU Time with user_sys_cpu_time parameter.
568 //
569 // If user_sys_cpu_time is true, user+sys time is returned.
570 // Otherwise, only user time is returned
571 static jlong current_thread_cpu_time(bool user_sys_cpu_time);
572 static jlong thread_cpu_time(Thread* t, bool user_sys_cpu_time);
574 // Return a bunch of info about the timers.
575 // Note that the returned info for these two functions may be different
576 // on some platforms
577 static void current_thread_cpu_time_info(jvmtiTimerInfo *info_ptr);
578 static void thread_cpu_time_info(jvmtiTimerInfo *info_ptr);
580 static bool is_thread_cpu_time_supported();
582 // System loadavg support. Returns -1 if load average cannot be obtained.
583 static int loadavg(double loadavg[], int nelem);
585 // Hook for os specific jvm options that we don't want to abort on seeing
586 static bool obsolete_option(const JavaVMOption *option);
588 // Platform dependent stuff
589 #include "incls/_os_pd.hpp.incl"
591 // debugging support (mostly used by debug.cpp but also fatal error handler)
592 static bool find(address pc, outputStream* st = tty); // OS specific function to make sense out of an address
594 static bool dont_yield(); // when true, JVM_Yield() is nop
595 static void print_statistics();
597 // Thread priority helpers (implemented in OS-specific part)
598 static OSReturn set_native_priority(Thread* thread, int native_prio);
599 static OSReturn get_native_priority(const Thread* const thread, int* priority_ptr);
600 static int java_to_os_priority[MaxPriority + 1];
601 // Hint to the underlying OS that a task switch would not be good.
602 // Void return because it's a hint and can fail.
603 static void hint_no_preempt();
605 // Used at creation if requested by the diagnostic flag PauseAtStartup.
606 // Causes the VM to wait until an external stimulus has been applied
607 // (for Unix, that stimulus is a signal, for Windows, an external
608 // ResumeThread call)
609 static void pause();
611 protected:
612 static long _rand_seed; // seed for random number generator
613 static int _processor_count; // number of processors
615 static char* format_boot_path(const char* format_string,
616 const char* home,
617 int home_len,
618 char fileSep,
619 char pathSep);
620 static bool set_boot_path(char fileSep, char pathSep);
621 static char** split_path(const char* path, int* n);
622 };
624 // Note that "PAUSE" is almost always used with synchronization
625 // so arguably we should provide Atomic::SpinPause() instead
626 // of the global SpinPause() with C linkage.
627 // It'd also be eligible for inlining on many platforms.
629 extern "C" int SpinPause () ;
630 extern "C" int SafeFetch32 (int * adr, int errValue) ;
631 extern "C" intptr_t SafeFetchN (intptr_t * adr, intptr_t errValue) ;