libjava/posix-threads.cc

   1 // posix-threads.cc - interface between libjava and POSIX threads.
   2
   3 /* Copyright (C) 1998, 1999, 2000  Free Software Foundation
   4
   5    This file is part of libgcj.
   6
   7 This software is copyrighted work licensed under the terms of the
   8 Libgcj License.  Please consult the file "LIBGCJ_LICENSE" for
   9 details.  */
  10
  11 // TO DO:
  12 // * Document signal handling limitations
  13
  14 #include <config.h>
  15
  16 // If we're using the Boehm GC, then we need to override some of the
  17 // thread primitives.  This is fairly gross.
  18 #ifdef HAVE_BOEHM_GC
  19 extern "C"
  20 {
  21 #include <gcconfig.h>
  22 #include <gc.h>
  23 };
  24 #endif /* HAVE_BOEHM_GC */
  25
  26 #include <stdlib.h>
  27 #include <time.h>
  28 #include <signal.h>
  29 #include <errno.h>
  30 #include <limits.h>
  31
  32 #include <gcj/cni.h>
  33 #include <jvm.h>
  34 #include <java/lang/Thread.h>
  35 #include <java/lang/System.h>
  36 #include <java/lang/Long.h>
  37 #include <java/lang/OutOfMemoryError.h>
  38
  39 // This is used to implement thread startup.
  40 struct starter
  41 {
  42   _Jv_ThreadStartFunc *method;
  43   _Jv_Thread_t *data;
  44 };
  45
  46 // This is the key used to map from the POSIX thread value back to the
  47 // Java object representing the thread.  The key is global to all
  48 // threads, so it is ok to make it a global here.
  49 pthread_key_t _Jv_ThreadKey;
  50
  51 // This is the key used to map from the POSIX thread value back to the
  52 // _Jv_Thread_t* representing the thread.
  53 pthread_key_t _Jv_ThreadDataKey;
  54
  55 // We keep a count of all non-daemon threads which are running.  When
  56 // this reaches zero, _Jv_ThreadWait returns.
  57 static pthread_mutex_t daemon_mutex;
  58 static pthread_cond_t daemon_cond;
  59 static int non_daemon_count;
  60
  61 // The signal to use when interrupting a thread.
  62 #ifdef LINUX_THREADS
  63   // LinuxThreads (prior to glibc 2.1) usurps both SIGUSR1 and SIGUSR2.
  64 #  define INTR SIGHUP
  65 #else /* LINUX_THREADS */
  66 #  define INTR SIGUSR2
  67 #endif /* LINUX_THREADS */
  68
  69 //
  70 // These are the flags that can appear in _Jv_Thread_t.
  71 //
  72
  73 // Thread started.
  74 #define FLAG_START   0x01
  75 // Thread is daemon.
  76 #define FLAG_DAEMON  0x02
  77
  78 \f
  79
  80 // Wait for the condition variable "CV" to be notified.
  81 // Return values:
  82 // 0: the condition was notified, or the timeout expired.
  83 // _JV_NOT_OWNER: the thread does not own the mutex "MU".
  84 // _JV_INTERRUPTED: the thread was interrupted. Its interrupted flag is set.
  85 int
  86 _Jv_CondWait (_Jv_ConditionVariable_t *cv, _Jv_Mutex_t *mu,
  87               jlong millis, jint nanos)
  88 {
  89   pthread_t self = pthread_self();
  90   if (mu->owner != self)
  91     return _JV_NOT_OWNER;
  92
  93   struct timespec ts;
  94   jlong m, startTime;
  95
  96   if (millis > 0 || nanos > 0)
  97     {
  98       startTime = java::lang::System::currentTimeMillis();
  99       m = millis + startTime;
 100       ts.tv_sec = m / 1000;
 101       ts.tv_nsec = ((m % 1000) * 1000000) + nanos;
 102     }
 103
 104   _Jv_Thread_t *current = _Jv_ThreadCurrentData ();
 105   java::lang::Thread *current_obj = _Jv_ThreadCurrent ();
 106
 107   pthread_mutex_lock (&current->wait_mutex);
 108
 109   // Now that we hold the wait mutex, check if this thread has been
 110   // interrupted already.
 111   if (current_obj->interrupt_flag)
 112     {
 113       pthread_mutex_unlock (&current->wait_mutex);
 114       return _JV_INTERRUPTED;
 115     }
 116
 117   // Add this thread to the cv's wait set.
 118   current->next = NULL;
 119
 120   if (cv->first == NULL)
 121     cv->first = current;
 122   else
 123     for (_Jv_Thread_t *t = cv->first;; t = t->next)
 124       {
 125         if (t->next == NULL)
 126           {
 127             t->next = current;
 128             break;
 129           }
 130       }
 131
 132   // Record the current lock depth, so it can be restored when we re-aquire it.
 133   int count = mu->count;
 134
 135   // Release the monitor mutex.
 136   mu->count = 0;
 137   mu->owner = 0;
 138   pthread_mutex_unlock (&mu->mutex);
 139
 140   int r = 0;
 141   bool done_sleeping = false;
 142
 143   while (! done_sleeping)
 144     {
 145       if (millis == 0 && nanos == 0)
 146         r = pthread_cond_wait (&current->wait_cond, &current->wait_mutex);
 147       else
 148         r = pthread_cond_timedwait (&current->wait_cond, &current->wait_mutex,
 149                                     &ts);
 150
 151       // In older glibc's (prior to 2.1.3), the cond_wait functions may
 152       // spuriously wake up on a signal. Catch that here.
 153       if (r != EINTR)
 154         done_sleeping = true;
 155     }
 156
 157   // Check for an interrupt *before* releasing the wait mutex.
 158   jboolean interrupted = current_obj->interrupt_flag;
 159
 160   pthread_mutex_unlock (&current->wait_mutex);
 161
 162   //  Reaquire the monitor mutex, and restore the lock count.
 163   pthread_mutex_lock (&mu->mutex);
 164   mu->owner = self;
 165   mu->count = count;
 166
 167   // If we were interrupted, or if a timeout occured, remove ourself from
 168   // the cv wait list now. (If we were notified normally, notify() will have
 169   // already taken care of this)
 170   if (r == ETIMEDOUT || interrupted)
 171     {
 172       _Jv_Thread_t *prev = NULL;
 173       for (_Jv_Thread_t *t = cv->first; t != NULL; t = t->next)
 174         {
 175           if (t == current)
 176             {
 177               if (prev != NULL)
 178                 prev->next = t->next;
 179               else
 180                 cv->first = t->next;
 181               t->next = NULL;
 182               break;
 183             }
 184           prev = t;
 185         }
 186       if (interrupted)
 187         return _JV_INTERRUPTED;
 188     }
 189
 190   return 0;
 191 }
 192
 193 int
 194 _Jv_CondNotify (_Jv_ConditionVariable_t *cv, _Jv_Mutex_t *mu)
 195 {
 196   if (_Jv_PthreadCheckMonitor (mu))
 197     return _JV_NOT_OWNER;
 198
 199   _Jv_Thread_t *target;
 200   _Jv_Thread_t *prev = NULL;
 201
 202   for (target = cv->first; target != NULL; target = target->next)
 203     {
 204       pthread_mutex_lock (&target->wait_mutex);
 205
 206       if (target->thread_obj->interrupt_flag)
 207         {
 208           // Don't notify a thread that has already been interrupted.
 209           pthread_mutex_unlock (&target->wait_mutex);
 210           prev = target;
 211           continue;
 212         }
 213
 214       pthread_cond_signal (&target->wait_cond);
 215       pthread_mutex_unlock (&target->wait_mutex);
 216
 217       // Two concurrent notify() calls must not be delivered to the same
 218       // thread, so remove the target thread from the cv wait list now.
 219       if (prev == NULL)
 220         cv->first = target->next;
 221       else
 222         prev->next = target->next;
 223
 224       target->next = NULL;
 225
 226       break;
 227     }
 228
 229   return 0;
 230 }
 231
 232 int
 233 _Jv_CondNotifyAll (_Jv_ConditionVariable_t *cv, _Jv_Mutex_t *mu)
 234 {
 235   if (_Jv_PthreadCheckMonitor (mu))
 236     return _JV_NOT_OWNER;
 237
 238   _Jv_Thread_t *target;
 239   _Jv_Thread_t *prev = NULL;
 240
 241   for (target = cv->first; target != NULL; target = target->next)
 242     {
 243       pthread_mutex_lock (&target->wait_mutex);
 244       pthread_cond_signal (&target->wait_cond);
 245       pthread_mutex_unlock (&target->wait_mutex);
 246
 247       if (prev != NULL)
 248         prev->next = NULL;
 249       prev = target;
 250     }
 251   if (prev != NULL)
 252     prev->next = NULL;
 253
 254   cv->first = NULL;
 255
 256   return 0;
 257 }
 258
 259 void
 260 _Jv_ThreadInterrupt (_Jv_Thread_t *data)
 261 {
 262   pthread_mutex_lock (&data->wait_mutex);
 263
 264   // Set the thread's interrupted flag *after* aquiring its wait_mutex. This
 265   // ensures that there are no races with the interrupt flag being set after
 266   // the waiting thread checks it and before pthread_cond_wait is entered.
 267   data->thread_obj->interrupt_flag = true;
 268
 269   // Interrupt blocking system calls using a signal.
 270 //  pthread_kill (data->thread, INTR);
 271
 272   pthread_cond_signal (&data->wait_cond);
 273
 274   pthread_mutex_unlock (&data->wait_mutex);
 275 }
 276
 277 static void
 278 handle_intr (int)
 279 {
 280   // Do nothing.
 281 }
 282
 283 void
 284 _Jv_InitThreads (void)
 285 {
 286   pthread_key_create (&_Jv_ThreadKey, NULL);
 287   pthread_key_create (&_Jv_ThreadDataKey, NULL);
 288   pthread_mutex_init (&daemon_mutex, NULL);
 289   pthread_cond_init (&daemon_cond, 0);
 290   non_daemon_count = 0;
 291
 292   // Arrange for the interrupt signal to interrupt system calls.
 293   struct sigaction act;
 294   act.sa_handler = handle_intr;
 295   sigemptyset (&act.sa_mask);
 296   act.sa_flags = 0;
 297   sigaction (INTR, &act, NULL);
 298 }
 299
 300 _Jv_Thread_t *
 301 _Jv_ThreadInitData (java::lang::Thread *obj)
 302 {
 303   _Jv_Thread_t *data = new _Jv_Thread_t;
 304   data->flags = 0;
 305   data->thread_obj = obj;
 306
 307   pthread_mutex_init (&data->wait_mutex, NULL);
 308   pthread_cond_init (&data->wait_cond, NULL);
 309
 310   return data;
 311 }
 312
 313 void
 314 _Jv_ThreadDestroyData (_Jv_Thread_t *data)
 315 {
 316   pthread_mutex_destroy (&data->wait_mutex);
 317   pthread_cond_destroy (&data->wait_cond);
 318   delete data;
 319 }
 320
 321 void
 322 _Jv_ThreadSetPriority (_Jv_Thread_t *data, jint prio)
 323 {
 324   if (data->flags & FLAG_START)
 325     {
 326       struct sched_param param;
 327
 328       param.sched_priority = prio;
 329       pthread_setschedparam (data->thread, SCHED_RR, &param);
 330     }
 331 }
 332
 333 // This function is called when a thread is started.  We don't arrange
 334 // to call the `run' method directly, because this function must
 335 // return a value.
 336 static void *
 337 really_start (void *x)
 338 {
 339   struct starter *info = (struct starter *) x;
 340
 341   pthread_setspecific (_Jv_ThreadKey, info->data->thread_obj);
 342   pthread_setspecific (_Jv_ThreadDataKey, info->data);
 343
 344   // glibc 2.1.3 doesn't set the value of `thread' until after start_routine
 345   // is called. Since it may need to be accessed from the new thread, work
 346   // around the potential race here by explicitly setting it again.
 347   info->data->thread = pthread_self ();
 348
 349   info->method (info->data->thread_obj);
 350
 351   if (! (info->data->flags & FLAG_DAEMON))
 352     {
 353       pthread_mutex_lock (&daemon_mutex);
 354       --non_daemon_count;
 355       if (! non_daemon_count)
 356         pthread_cond_signal (&daemon_cond);
 357       pthread_mutex_unlock (&daemon_mutex);
 358     }
 359
 360   return NULL;
 361 }
 362
 363 void
 364 _Jv_ThreadStart (java::lang::Thread *thread, _Jv_Thread_t *data,
 365                  _Jv_ThreadStartFunc *meth)
 366 {
 367   struct sched_param param;
 368   pthread_attr_t attr;
 369   struct starter *info;
 370
 371   if (data->flags & FLAG_START)
 372     return;
 373   data->flags |= FLAG_START;
 374
 375   param.sched_priority = thread->getPriority();
 376
 377   pthread_attr_init (&attr);
 378   pthread_attr_setschedparam (&attr, &param);
 379   pthread_attr_setdetachstate (&attr, PTHREAD_CREATE_DETACHED);
 380
 381   // FIXME: handle marking the info object for GC.
 382   info = (struct starter *) _Jv_AllocBytes (sizeof (struct starter));
 383   info->method = meth;
 384   info->data = data;
 385
 386   if (! thread->isDaemon())
 387     {
 388       pthread_mutex_lock (&daemon_mutex);
 389       ++non_daemon_count;
 390       pthread_mutex_unlock (&daemon_mutex);
 391     }
 392   else
 393     data->flags |= FLAG_DAEMON;
 394   int r = pthread_create (&data->thread, &attr, really_start, (void *) info);
 395
 396   pthread_attr_destroy (&attr);
 397
 398   if (r)
 399     {
 400       const char* msg = "Cannot create additional threads";
 401       JvThrow (new java::lang::OutOfMemoryError (JvNewStringUTF (msg)));
 402     }
 403 }
 404
 405 void
 406 _Jv_ThreadWait (void)
 407 {
 408   pthread_mutex_lock (&daemon_mutex);
 409   if (non_daemon_count)
 410     pthread_cond_wait (&daemon_cond, &daemon_mutex);
 411   pthread_mutex_unlock (&daemon_mutex);
 412 }