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 bool
  78 sys_thread_equal (sys_thread_t t, sys_thread_t u)
  79 {
  80   return t == u;
  81 }
  82
  83 int
  84 sys_thread_create (sys_thread_t *t, const char *name,
  85                    thread_creation_function *func, void *datum)
  86 {
  87   return 0;
  88 }
  89
  90 void
  91 sys_thread_yield (void)
  92 {
  93 }
  94
  95 #elif defined (HAVE_PTHREAD)
  96
  97 #include <sched.h>
  98
  99 #ifdef HAVE_SYS_PRCTL_H
 100 #include <sys/prctl.h>
 101 #endif
 102
 103 void
 104 sys_mutex_init (sys_mutex_t *mutex)
 105 {
 106   pthread_mutex_init (mutex, NULL);
 107 }
 108
 109 void
 110 sys_mutex_lock (sys_mutex_t *mutex)
 111 {
 112   pthread_mutex_lock (mutex);
 113 }
 114
 115 void
 116 sys_mutex_unlock (sys_mutex_t *mutex)
 117 {
 118   pthread_mutex_unlock (mutex);
 119 }
 120
 121 void
 122 sys_cond_init (sys_cond_t *cond)
 123 {
 124   pthread_cond_init (cond, NULL);
 125 }
 126
 127 void
 128 sys_cond_wait (sys_cond_t *cond, sys_mutex_t *mutex)
 129 {
 130   pthread_cond_wait (cond, mutex);
 131 }
 132
 133 void
 134 sys_cond_signal (sys_cond_t *cond)
 135 {
 136   pthread_cond_signal (cond);
 137 }
 138
 139 void
 140 sys_cond_broadcast (sys_cond_t *cond)
 141 {
 142   pthread_cond_broadcast (cond);
 143 #ifdef HAVE_NS
 144   /* Send an app defined event to break out of the NS run loop.
 145      It seems that if ns_select is running the NS run loop, this
 146      broadcast has no effect until the loop is done, breaking a couple
 147      of tests in thread-tests.el. */
 148   ns_run_loop_break ();
 149 #endif
 150 }
 151
 152 void
 153 sys_cond_destroy (sys_cond_t *cond)
 154 {
 155   pthread_cond_destroy (cond);
 156 }
 157
 158 sys_thread_t
 159 sys_thread_self (void)
 160 {
 161   return pthread_self ();
 162 }
 163
 164 bool
 165 sys_thread_equal (sys_thread_t t, sys_thread_t u)
 166 {
 167   return pthread_equal (t, u);
 168 }
 169
 170 int
 171 sys_thread_create (sys_thread_t *thread_ptr, const char *name,
 172                    thread_creation_function *func, void *arg)
 173 {
 174   pthread_attr_t attr;
 175   int result = 0;
 176
 177   if (pthread_attr_init (&attr))
 178     return 0;
 179
 180   /* Avoid crash on macOS with deeply nested GC (Bug#30364).  */
 181   size_t stack_size;
 182   size_t required_stack_size = sizeof (void *) * 1024 * 1024;
 183   if (pthread_attr_getstacksize (&attr, &stack_size) == 0
 184       && stack_size < required_stack_size)
 185     pthread_attr_setstacksize (&attr, required_stack_size);
 186
 187   if (!pthread_attr_setdetachstate (&attr, PTHREAD_CREATE_DETACHED))
 188     {
 189       result = pthread_create (thread_ptr, &attr, func, arg) == 0;
 190 #if defined (HAVE_SYS_PRCTL_H) && defined (HAVE_PRCTL) && defined (PR_SET_NAME)
 191       if (result && name != NULL)
 192         prctl (PR_SET_NAME, name);
 193 #endif
 194     }
 195
 196   pthread_attr_destroy (&attr);
 197
 198   return result;
 199 }
 200
 201 void
 202 sys_thread_yield (void)
 203 {
 204   sched_yield ();
 205 }
 206
 207 #elif defined (WINDOWSNT)
 208
 209 #include <w32term.h>
 210
 211 /* Cannot include <process.h> because of the local header by the same
 212    name, sigh.  */
 213 uintptr_t _beginthread (void (__cdecl *)(void *), unsigned, void *);
 214
 215 /* Mutexes are implemented as critical sections, because they are
 216    faster than Windows mutex objects (implemented in userspace), and
 217    satisfy the requirements, since we only need to synchronize within a
 218    single process.  */
 219 void
 220 sys_mutex_init (sys_mutex_t *mutex)
 221 {
 222   InitializeCriticalSection ((LPCRITICAL_SECTION)mutex);
 223 }
 224
 225 void
 226 sys_mutex_lock (sys_mutex_t *mutex)
 227 {
 228   /* FIXME: What happens if the owning thread exits without releasing
 229      the mutex?  According to MSDN, the result is undefined behavior.  */
 230   EnterCriticalSection ((LPCRITICAL_SECTION)mutex);
 231 }
 232
 233 void
 234 sys_mutex_unlock (sys_mutex_t *mutex)
 235 {
 236   LeaveCriticalSection ((LPCRITICAL_SECTION)mutex);
 237 }
 238
 239 void
 240 sys_cond_init (sys_cond_t *cond)
 241 {
 242   cond->initialized = false;
 243   cond->wait_count = 0;
 244   /* Auto-reset event for signal.  */
 245   cond->events[CONDV_SIGNAL] = CreateEvent (NULL, FALSE, FALSE, NULL);
 246   /* Manual-reset event for broadcast.  */
 247   cond->events[CONDV_BROADCAST] = CreateEvent (NULL, TRUE, FALSE, NULL);
 248   if (!cond->events[CONDV_SIGNAL] || !cond->events[CONDV_BROADCAST])
 249     return;
 250   InitializeCriticalSection ((LPCRITICAL_SECTION)&cond->wait_count_lock);
 251   cond->initialized = true;
 252 }
 253
 254 void
 255 sys_cond_wait (sys_cond_t *cond, sys_mutex_t *mutex)
 256 {
 257   DWORD wait_result;
 258   bool last_thread_waiting;
 259
 260   if (!cond->initialized)
 261     return;
 262
 263   /* Increment the wait count avoiding race conditions.  */
 264   EnterCriticalSection ((LPCRITICAL_SECTION)&cond->wait_count_lock);
 265   cond->wait_count++;
 266   LeaveCriticalSection ((LPCRITICAL_SECTION)&cond->wait_count_lock);
 267
 268   /* Release the mutex and wait for either the signal or the broadcast
 269      event.  */
 270   LeaveCriticalSection ((LPCRITICAL_SECTION)mutex);
 271   wait_result = WaitForMultipleObjects (2, cond->events, FALSE, INFINITE);
 272
 273   /* Decrement the wait count and see if we are the last thread
 274      waiting on the condition variable.  */
 275   EnterCriticalSection ((LPCRITICAL_SECTION)&cond->wait_count_lock);
 276   cond->wait_count--;
 277   last_thread_waiting =
 278     wait_result == WAIT_OBJECT_0 + CONDV_BROADCAST
 279     && cond->wait_count == 0;
 280   LeaveCriticalSection ((LPCRITICAL_SECTION)&cond->wait_count_lock);
 281
 282   /* Broadcast uses a manual-reset event, so when the last thread is
 283      released, we must manually reset that event.  */
 284   if (last_thread_waiting)
 285     ResetEvent (cond->events[CONDV_BROADCAST]);
 286
 287   /* Per the API, re-acquire the mutex.  */
 288   EnterCriticalSection ((LPCRITICAL_SECTION)mutex);
 289 }
 290
 291 void
 292 sys_cond_signal (sys_cond_t *cond)
 293 {
 294   bool threads_waiting;
 295
 296   if (!cond->initialized)
 297     return;
 298
 299   EnterCriticalSection ((LPCRITICAL_SECTION)&cond->wait_count_lock);
 300   threads_waiting = cond->wait_count > 0;
 301   LeaveCriticalSection ((LPCRITICAL_SECTION)&cond->wait_count_lock);
 302
 303   if (threads_waiting)
 304     SetEvent (cond->events[CONDV_SIGNAL]);
 305 }
 306
 307 void
 308 sys_cond_broadcast (sys_cond_t *cond)
 309 {
 310   bool threads_waiting;
 311
 312   if (!cond->initialized)
 313     return;
 314
 315   EnterCriticalSection ((LPCRITICAL_SECTION)&cond->wait_count_lock);
 316   threads_waiting = cond->wait_count > 0;
 317   LeaveCriticalSection ((LPCRITICAL_SECTION)&cond->wait_count_lock);
 318
 319   if (threads_waiting)
 320     SetEvent (cond->events[CONDV_BROADCAST]);
 321 }
 322
 323 void
 324 sys_cond_destroy (sys_cond_t *cond)
 325 {
 326   if (cond->events[CONDV_SIGNAL])
 327     CloseHandle (cond->events[CONDV_SIGNAL]);
 328   if (cond->events[CONDV_BROADCAST])
 329     CloseHandle (cond->events[CONDV_BROADCAST]);
 330
 331   if (!cond->initialized)
 332     return;
 333
 334   /* FIXME: What if wait_count is non-zero, i.e. there are still
 335      threads waiting on this condition variable?  */
 336   DeleteCriticalSection ((LPCRITICAL_SECTION)&cond->wait_count_lock);
 337 }
 338
 339 sys_thread_t
 340 sys_thread_self (void)
 341 {
 342   return (sys_thread_t) GetCurrentThreadId ();
 343 }
 344
 345 bool
 346 sys_thread_equal (sys_thread_t t, sys_thread_t u)
 347 {
 348   return t == u;
 349 }
 350
 351 static thread_creation_function *thread_start_address;
 352
 353 /* _beginthread wants a void function, while we are passed a function
 354    that returns a pointer.  So we use a wrapper.  See the command in
 355    w32term.h about the need for ALIGN_STACK attribute.  */
 356 static void ALIGN_STACK
 357 w32_beginthread_wrapper (void *arg)
 358 {
 359   (void)thread_start_address (arg);
 360 }
 361
 362 int
 363 sys_thread_create (sys_thread_t *thread_ptr, const char *name,
 364                    thread_creation_function *func, void *arg)
 365 {
 366   /* FIXME: Do threads that run Lisp require some minimum amount of
 367      stack?  Zero here means each thread will get the same amount as
 368      the main program.  On GNU/Linux, it seems like the stack is 2MB
 369      by default, overridden by RLIMIT_STACK at program start time.
 370      Not sure what to do with this.  See also the comment in
 371      w32proc.c:new_child.  */
 372   const unsigned stack_size = 0;
 373   uintptr_t thandle;
 374
 375   thread_start_address = func;
 376
 377   /* We use _beginthread rather than CreateThread because the former
 378      arranges for the thread handle to be automatically closed when
 379      the thread exits, thus preventing handle leaks and/or the need to
 380      track all the threads and close their handles when they exit.
 381      Also, MSDN seems to imply that code which uses CRT _must_ call
 382      _beginthread, although if that is true, we already violate that
 383      rule in many places...  */
 384   thandle = _beginthread (w32_beginthread_wrapper, stack_size, arg);
 385   if (thandle == (uintptr_t)-1L)
 386     return 0;
 387
 388   /* Kludge alert!  We use the Windows thread ID, an unsigned 32-bit
 389      number, as the sys_thread_t type, because that ID is the only
 390      unique identifier of a thread on Windows.  But _beginthread
 391      returns a handle of the thread, and there's no easy way of
 392      getting the thread ID given a handle (GetThreadId is available
 393      only since Vista, so we cannot use it portably).  Fortunately,
 394      the value returned by sys_thread_create is not used by its
 395      callers; instead, run_thread, which runs in the context of the
 396      new thread, calls sys_thread_self and uses its return value;
 397      sys_thread_self in this implementation calls GetCurrentThreadId.
 398      Therefore, we return some more or less arbitrary value of the
 399      thread ID from this function. */
 400   *thread_ptr = thandle & 0xFFFFFFFF;
 401   return 1;
 402 }
 403
 404 void
 405 sys_thread_yield (void)
 406 {
 407   Sleep (0);
 408 }
 409
 410 #else
 411
 412 #error port me
 413
 414 #endif