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   if (!pthread_attr_setdetachstate (&attr, PTHREAD_CREATE_DETACHED))
 181     {
 182       result = pthread_create (thread_ptr, &attr, func, arg) == 0;
 183 #if defined (HAVE_SYS_PRCTL_H) && defined (HAVE_PRCTL) && defined (PR_SET_NAME)
 184       if (result && name != NULL)
 185         prctl (PR_SET_NAME, name);
 186 #endif
 187     }
 188
 189   pthread_attr_destroy (&attr);
 190
 191   return result;
 192 }
 193
 194 void
 195 sys_thread_yield (void)
 196 {
 197   sched_yield ();
 198 }
 199
 200 #elif defined (WINDOWSNT)
 201
 202 #include <w32term.h>
 203
 204 /* Cannot include <process.h> because of the local header by the same
 205    name, sigh.  */
 206 uintptr_t _beginthread (void (__cdecl *)(void *), unsigned, void *);
 207
 208 /* Mutexes are implemented as critical sections, because they are
 209    faster than Windows mutex objects (implemented in userspace), and
 210    satisfy the requirements, since we only need to synchronize within a
 211    single process.  */
 212 void
 213 sys_mutex_init (sys_mutex_t *mutex)
 214 {
 215   InitializeCriticalSection ((LPCRITICAL_SECTION)mutex);
 216 }
 217
 218 void
 219 sys_mutex_lock (sys_mutex_t *mutex)
 220 {
 221   /* FIXME: What happens if the owning thread exits without releasing
 222      the mutex?  According to MSDN, the result is undefined behavior.  */
 223   EnterCriticalSection ((LPCRITICAL_SECTION)mutex);
 224 }
 225
 226 void
 227 sys_mutex_unlock (sys_mutex_t *mutex)
 228 {
 229   LeaveCriticalSection ((LPCRITICAL_SECTION)mutex);
 230 }
 231
 232 void
 233 sys_cond_init (sys_cond_t *cond)
 234 {
 235   cond->initialized = false;
 236   cond->wait_count = 0;
 237   /* Auto-reset event for signal.  */
 238   cond->events[CONDV_SIGNAL] = CreateEvent (NULL, FALSE, FALSE, NULL);
 239   /* Manual-reset event for broadcast.  */
 240   cond->events[CONDV_BROADCAST] = CreateEvent (NULL, TRUE, FALSE, NULL);
 241   if (!cond->events[CONDV_SIGNAL] || !cond->events[CONDV_BROADCAST])
 242     return;
 243   InitializeCriticalSection ((LPCRITICAL_SECTION)&cond->wait_count_lock);
 244   cond->initialized = true;
 245 }
 246
 247 void
 248 sys_cond_wait (sys_cond_t *cond, sys_mutex_t *mutex)
 249 {
 250   DWORD wait_result;
 251   bool last_thread_waiting;
 252
 253   if (!cond->initialized)
 254     return;
 255
 256   /* Increment the wait count avoiding race conditions.  */
 257   EnterCriticalSection ((LPCRITICAL_SECTION)&cond->wait_count_lock);
 258   cond->wait_count++;
 259   LeaveCriticalSection ((LPCRITICAL_SECTION)&cond->wait_count_lock);
 260
 261   /* Release the mutex and wait for either the signal or the broadcast
 262      event.  */
 263   LeaveCriticalSection ((LPCRITICAL_SECTION)mutex);
 264   wait_result = WaitForMultipleObjects (2, cond->events, FALSE, INFINITE);
 265
 266   /* Decrement the wait count and see if we are the last thread
 267      waiting on the condition variable.  */
 268   EnterCriticalSection ((LPCRITICAL_SECTION)&cond->wait_count_lock);
 269   cond->wait_count--;
 270   last_thread_waiting =
 271     wait_result == WAIT_OBJECT_0 + CONDV_BROADCAST
 272     && cond->wait_count == 0;
 273   LeaveCriticalSection ((LPCRITICAL_SECTION)&cond->wait_count_lock);
 274
 275   /* Broadcast uses a manual-reset event, so when the last thread is
 276      released, we must manually reset that event.  */
 277   if (last_thread_waiting)
 278     ResetEvent (cond->events[CONDV_BROADCAST]);
 279
 280   /* Per the API, re-acquire the mutex.  */
 281   EnterCriticalSection ((LPCRITICAL_SECTION)mutex);
 282 }
 283
 284 void
 285 sys_cond_signal (sys_cond_t *cond)
 286 {
 287   bool threads_waiting;
 288
 289   if (!cond->initialized)
 290     return;
 291
 292   EnterCriticalSection ((LPCRITICAL_SECTION)&cond->wait_count_lock);
 293   threads_waiting = cond->wait_count > 0;
 294   LeaveCriticalSection ((LPCRITICAL_SECTION)&cond->wait_count_lock);
 295
 296   if (threads_waiting)
 297     SetEvent (cond->events[CONDV_SIGNAL]);
 298 }
 299
 300 void
 301 sys_cond_broadcast (sys_cond_t *cond)
 302 {
 303   bool threads_waiting;
 304
 305   if (!cond->initialized)
 306     return;
 307
 308   EnterCriticalSection ((LPCRITICAL_SECTION)&cond->wait_count_lock);
 309   threads_waiting = cond->wait_count > 0;
 310   LeaveCriticalSection ((LPCRITICAL_SECTION)&cond->wait_count_lock);
 311
 312   if (threads_waiting)
 313     SetEvent (cond->events[CONDV_BROADCAST]);
 314 }
 315
 316 void
 317 sys_cond_destroy (sys_cond_t *cond)
 318 {
 319   if (cond->events[CONDV_SIGNAL])
 320     CloseHandle (cond->events[CONDV_SIGNAL]);
 321   if (cond->events[CONDV_BROADCAST])
 322     CloseHandle (cond->events[CONDV_BROADCAST]);
 323
 324   if (!cond->initialized)
 325     return;
 326
 327   /* FIXME: What if wait_count is non-zero, i.e. there are still
 328      threads waiting on this condition variable?  */
 329   DeleteCriticalSection ((LPCRITICAL_SECTION)&cond->wait_count_lock);
 330 }
 331
 332 sys_thread_t
 333 sys_thread_self (void)
 334 {
 335   return (sys_thread_t) GetCurrentThreadId ();
 336 }
 337
 338 bool
 339 sys_thread_equal (sys_thread_t t, sys_thread_t u)
 340 {
 341   return t == u;
 342 }
 343
 344 static thread_creation_function *thread_start_address;
 345
 346 /* _beginthread wants a void function, while we are passed a function
 347    that returns a pointer.  So we use a wrapper.  See the command in
 348    w32term.h about the need for ALIGN_STACK attribute.  */
 349 static void ALIGN_STACK
 350 w32_beginthread_wrapper (void *arg)
 351 {
 352   (void)thread_start_address (arg);
 353 }
 354
 355 int
 356 sys_thread_create (sys_thread_t *thread_ptr, const char *name,
 357                    thread_creation_function *func, void *arg)
 358 {
 359   /* FIXME: Do threads that run Lisp require some minimum amount of
 360      stack?  Zero here means each thread will get the same amount as
 361      the main program.  On GNU/Linux, it seems like the stack is 2MB
 362      by default, overridden by RLIMIT_STACK at program start time.
 363      Not sure what to do with this.  See also the comment in
 364      w32proc.c:new_child.  */
 365   const unsigned stack_size = 0;
 366   uintptr_t thandle;
 367
 368   thread_start_address = func;
 369
 370   /* We use _beginthread rather than CreateThread because the former
 371      arranges for the thread handle to be automatically closed when
 372      the thread exits, thus preventing handle leaks and/or the need to
 373      track all the threads and close their handles when they exit.
 374      Also, MSDN seems to imply that code which uses CRT _must_ call
 375      _beginthread, although if that is true, we already violate that
 376      rule in many places...  */
 377   thandle = _beginthread (w32_beginthread_wrapper, stack_size, arg);
 378   if (thandle == (uintptr_t)-1L)
 379     return 0;
 380
 381   /* Kludge alert!  We use the Windows thread ID, an unsigned 32-bit
 382      number, as the sys_thread_t type, because that ID is the only
 383      unique identifier of a thread on Windows.  But _beginthread
 384      returns a handle of the thread, and there's no easy way of
 385      getting the thread ID given a handle (GetThreadId is available
 386      only since Vista, so we cannot use it portably).  Fortunately,
 387      the value returned by sys_thread_create is not used by its
 388      callers; instead, run_thread, which runs in the context of the
 389      new thread, calls sys_thread_self and uses its return value;
 390      sys_thread_self in this implementation calls GetCurrentThreadId.
 391      Therefore, we return some more or less arbitrary value of the
 392      thread ID from this function. */
 393   *thread_ptr = thandle & 0xFFFFFFFF;
 394   return 1;
 395 }
 396
 397 void
 398 sys_thread_yield (void)
 399 {
 400   Sleep (0);
 401 }
 402
 403 #else
 404
 405 #error port me
 406
 407 #endif