src/systhread.c

   1 /* System thread definitions
   2 Copyright (C) 2012-2018 Free Software Foundation, Inc.
   3
   4 This file is part of GNU Emacs.
   5
   6 GNU Emacs is free software: you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation, either version 3 of the License, or
   9 (at your option) any later version.
  10
  11 GNU Emacs is distributed in the hope that it will be useful,
  12 but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 GNU General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.  */
  18
  19 #include <config.h>
  20 #include <setjmp.h>
  21 #include "lisp.h"
  22
  23 #ifdef HAVE_NS
  24 #include "nsterm.h"
  25 #endif
  26
  27 #ifndef THREADS_ENABLED
  28
  29 void
  30 sys_mutex_init (sys_mutex_t *m)
  31 {
  32   *m = 0;
  33 }
  34
  35 void
  36 sys_mutex_lock (sys_mutex_t *m)
  37 {
  38 }
  39
  40 void
  41 sys_mutex_unlock (sys_mutex_t *m)
  42 {
  43 }
  44
  45 void
  46 sys_cond_init (sys_cond_t *c)
  47 {
  48   *c = 0;
  49 }
  50
  51 void
  52 sys_cond_wait (sys_cond_t *c, sys_mutex_t *m)
  53 {
  54 }
  55
  56 void
  57 sys_cond_signal (sys_cond_t *c)
  58 {
  59 }
  60
  61 void
  62 sys_cond_broadcast (sys_cond_t *c)
  63 {
  64 }
  65
  66 void
  67 sys_cond_destroy (sys_cond_t *c)
  68 {
  69 }
  70
  71 sys_thread_t
  72 sys_thread_self (void)
  73 {
  74   return 0;
  75 }
  76
  77 int
  78 sys_thread_create (sys_thread_t *t, const char *name,
  79                    thread_creation_function *func, void *datum)
  80 {
  81   return 0;
  82 }
  83
  84 void
  85 sys_thread_yield (void)
  86 {
  87 }
  88
  89 #elif defined (HAVE_PTHREAD)
  90
  91 #include <sched.h>
  92
  93 #ifdef HAVE_SYS_PRCTL_H
  94 #include <sys/prctl.h>
  95 #endif
  96
  97 void
  98 sys_mutex_init (sys_mutex_t *mutex)
  99 {
 100   pthread_mutex_init (mutex, NULL);
 101 }
 102
 103 void
 104 sys_mutex_lock (sys_mutex_t *mutex)
 105 {
 106   pthread_mutex_lock (mutex);
 107 }
 108
 109 void
 110 sys_mutex_unlock (sys_mutex_t *mutex)
 111 {
 112   pthread_mutex_unlock (mutex);
 113 }
 114
 115 void
 116 sys_cond_init (sys_cond_t *cond)
 117 {
 118   pthread_cond_init (cond, NULL);
 119 }
 120
 121 void
 122 sys_cond_wait (sys_cond_t *cond, sys_mutex_t *mutex)
 123 {
 124   pthread_cond_wait (cond, mutex);
 125 }
 126
 127 void
 128 sys_cond_signal (sys_cond_t *cond)
 129 {
 130   pthread_cond_signal (cond);
 131 }
 132
 133 void
 134 sys_cond_broadcast (sys_cond_t *cond)
 135 {
 136   pthread_cond_broadcast (cond);
 137 #ifdef HAVE_NS
 138   /* Send an app defined event to break out of the NS run loop.
 139      It seems that if ns_select is running the NS run loop, this
 140      broadcast has no effect until the loop is done, breaking a couple
 141      of tests in thread-tests.el. */
 142   ns_run_loop_break ();
 143 #endif
 144 }
 145
 146 void
 147 sys_cond_destroy (sys_cond_t *cond)
 148 {
 149   pthread_cond_destroy (cond);
 150 }
 151
 152 sys_thread_t
 153 sys_thread_self (void)
 154 {
 155   return pthread_self ();
 156 }
 157
 158 int
 159 sys_thread_create (sys_thread_t *thread_ptr, const char *name,
 160                    thread_creation_function *func, void *arg)
 161 {
 162   pthread_attr_t attr;
 163   int result = 0;
 164
 165   if (pthread_attr_init (&attr))
 166     return 0;
 167
 168 #ifdef DARWIN_OS
 169   /* Avoid crash on macOS with deeply nested GC (Bug#30364).  */
 170   size_t stack_size;
 171   size_t required_stack_size = sizeof (void *) * 1024 * 1024;
 172   if (pthread_attr_getstacksize (&attr, &stack_size) == 0
 173       && stack_size < required_stack_size)
 174     pthread_attr_setstacksize (&attr, required_stack_size);
 175 #endif
 176
 177   if (!pthread_attr_setdetachstate (&attr, PTHREAD_CREATE_DETACHED))
 178     {
 179       result = pthread_create (thread_ptr, &attr, func, arg) == 0;
 180 #if defined (HAVE_SYS_PRCTL_H) && defined (HAVE_PRCTL) && defined (PR_SET_NAME)
 181       if (result && name != NULL)
 182         prctl (PR_SET_NAME, name);
 183 #endif
 184     }
 185
 186   pthread_attr_destroy (&attr);
 187
 188   return result;
 189 }
 190
 191 void
 192 sys_thread_yield (void)
 193 {
 194   sched_yield ();
 195 }
 196
 197 #elif defined (WINDOWSNT)
 198
 199 #include <w32term.h>
 200
 201 /* Cannot include <process.h> because of the local header by the same
 202    name, sigh.  */
 203 uintptr_t _beginthread (void (__cdecl *)(void *), unsigned, void *);
 204
 205 /* Mutexes are implemented as critical sections, because they are
 206    faster than Windows mutex objects (implemented in userspace), and
 207    satisfy the requirements, since we only need to synchronize within a
 208    single process.  */
 209 void
 210 sys_mutex_init (sys_mutex_t *mutex)
 211 {
 212   InitializeCriticalSection ((LPCRITICAL_SECTION)mutex);
 213 }
 214
 215 void
 216 sys_mutex_lock (sys_mutex_t *mutex)
 217 {
 218   /* FIXME: What happens if the owning thread exits without releasing
 219      the mutex?  According to MSDN, the result is undefined behavior.  */
 220   EnterCriticalSection ((LPCRITICAL_SECTION)mutex);
 221 }
 222
 223 void
 224 sys_mutex_unlock (sys_mutex_t *mutex)
 225 {
 226   LeaveCriticalSection ((LPCRITICAL_SECTION)mutex);
 227 }
 228
 229 void
 230 sys_cond_init (sys_cond_t *cond)
 231 {
 232   cond->initialized = false;
 233   cond->wait_count = 0;
 234   /* Auto-reset event for signal.  */
 235   cond->events[CONDV_SIGNAL] = CreateEvent (NULL, FALSE, FALSE, NULL);
 236   /* Manual-reset event for broadcast.  */
 237   cond->events[CONDV_BROADCAST] = CreateEvent (NULL, TRUE, FALSE, NULL);
 238   if (!cond->events[CONDV_SIGNAL] || !cond->events[CONDV_BROADCAST])
 239     return;
 240   InitializeCriticalSection ((LPCRITICAL_SECTION)&cond->wait_count_lock);
 241   cond->initialized = true;
 242 }
 243
 244 void
 245 sys_cond_wait (sys_cond_t *cond, sys_mutex_t *mutex)
 246 {
 247   DWORD wait_result;
 248   bool last_thread_waiting;
 249
 250   if (!cond->initialized)
 251     return;
 252
 253   /* Increment the wait count avoiding race conditions.  */
 254   EnterCriticalSection ((LPCRITICAL_SECTION)&cond->wait_count_lock);
 255   cond->wait_count++;
 256   LeaveCriticalSection ((LPCRITICAL_SECTION)&cond->wait_count_lock);
 257
 258   /* Release the mutex and wait for either the signal or the broadcast
 259      event.  */
 260   LeaveCriticalSection ((LPCRITICAL_SECTION)mutex);
 261   wait_result = WaitForMultipleObjects (2, cond->events, FALSE, INFINITE);
 262
 263   /* Decrement the wait count and see if we are the last thread
 264      waiting on the condition variable.  */
 265   EnterCriticalSection ((LPCRITICAL_SECTION)&cond->wait_count_lock);
 266   cond->wait_count--;
 267   last_thread_waiting =
 268     wait_result == WAIT_OBJECT_0 + CONDV_BROADCAST
 269     && cond->wait_count == 0;
 270   LeaveCriticalSection ((LPCRITICAL_SECTION)&cond->wait_count_lock);
 271
 272   /* Broadcast uses a manual-reset event, so when the last thread is
 273      released, we must manually reset that event.  */
 274   if (last_thread_waiting)
 275     ResetEvent (cond->events[CONDV_BROADCAST]);
 276
 277   /* Per the API, re-acquire the mutex.  */
 278   EnterCriticalSection ((LPCRITICAL_SECTION)mutex);
 279 }
 280
 281 void
 282 sys_cond_signal (sys_cond_t *cond)
 283 {
 284   bool threads_waiting;
 285
 286   if (!cond->initialized)
 287     return;
 288
 289   EnterCriticalSection ((LPCRITICAL_SECTION)&cond->wait_count_lock);
 290   threads_waiting = cond->wait_count > 0;
 291   LeaveCriticalSection ((LPCRITICAL_SECTION)&cond->wait_count_lock);
 292
 293   if (threads_waiting)
 294     SetEvent (cond->events[CONDV_SIGNAL]);
 295 }
 296
 297 void
 298 sys_cond_broadcast (sys_cond_t *cond)
 299 {
 300   bool threads_waiting;
 301
 302   if (!cond->initialized)
 303     return;
 304
 305   EnterCriticalSection ((LPCRITICAL_SECTION)&cond->wait_count_lock);
 306   threads_waiting = cond->wait_count > 0;
 307   LeaveCriticalSection ((LPCRITICAL_SECTION)&cond->wait_count_lock);
 308
 309   if (threads_waiting)
 310     SetEvent (cond->events[CONDV_BROADCAST]);
 311 }
 312
 313 void
 314 sys_cond_destroy (sys_cond_t *cond)
 315 {
 316   if (cond->events[CONDV_SIGNAL])
 317     CloseHandle (cond->events[CONDV_SIGNAL]);
 318   if (cond->events[CONDV_BROADCAST])
 319     CloseHandle (cond->events[CONDV_BROADCAST]);
 320
 321   if (!cond->initialized)
 322     return;
 323
 324   /* FIXME: What if wait_count is non-zero, i.e. there are still
 325      threads waiting on this condition variable?  */
 326   DeleteCriticalSection ((LPCRITICAL_SECTION)&cond->wait_count_lock);
 327 }
 328
 329 sys_thread_t
 330 sys_thread_self (void)
 331 {
 332   return (sys_thread_t) GetCurrentThreadId ();
 333 }
 334
 335 static thread_creation_function *thread_start_address;
 336
 337 /* _beginthread wants a void function, while we are passed a function
 338    that returns a pointer.  So we use a wrapper.  See the command in
 339    w32term.h about the need for ALIGN_STACK attribute.  */
 340 static void ALIGN_STACK
 341 w32_beginthread_wrapper (void *arg)
 342 {
 343   (void)thread_start_address (arg);
 344 }
 345
 346 int
 347 sys_thread_create (sys_thread_t *thread_ptr, const char *name,
 348                    thread_creation_function *func, void *arg)
 349 {
 350   /* FIXME: Do threads that run Lisp require some minimum amount of
 351      stack?  Zero here means each thread will get the same amount as
 352      the main program.  On GNU/Linux, it seems like the stack is 2MB
 353      by default, overridden by RLIMIT_STACK at program start time.
 354      Not sure what to do with this.  See also the comment in
 355      w32proc.c:new_child.  */
 356   const unsigned stack_size = 0;
 357   uintptr_t thandle;
 358
 359   thread_start_address = func;
 360
 361   /* We use _beginthread rather than CreateThread because the former
 362      arranges for the thread handle to be automatically closed when
 363      the thread exits, thus preventing handle leaks and/or the need to
 364      track all the threads and close their handles when they exit.
 365      Also, MSDN seems to imply that code which uses CRT _must_ call
 366      _beginthread, although if that is true, we already violate that
 367      rule in many places...  */
 368   thandle = _beginthread (w32_beginthread_wrapper, stack_size, arg);
 369   if (thandle == (uintptr_t)-1L)
 370     return 0;
 371
 372   /* Kludge alert!  We use the Windows thread ID, an unsigned 32-bit
 373      number, as the sys_thread_t type, because that ID is the only
 374      unique identifier of a thread on Windows.  But _beginthread
 375      returns a handle of the thread, and there's no easy way of
 376      getting the thread ID given a handle (GetThreadId is available
 377      only since Vista, so we cannot use it portably).  Fortunately,
 378      the value returned by sys_thread_create is not used by its
 379      callers; instead, run_thread, which runs in the context of the
 380      new thread, calls sys_thread_self and uses its return value;
 381      sys_thread_self in this implementation calls GetCurrentThreadId.
 382      Therefore, we return some more or less arbitrary value of the
 383      thread ID from this function. */
 384   *thread_ptr = thandle & 0xFFFFFFFF;
 385   return 1;
 386 }
 387
 388 void
 389 sys_thread_yield (void)
 390 {
 391   Sleep (0);
 392 }
 393
 394 #else
 395
 396 #error port me
 397
 398 #endif