libjava/posix-threads.cc

   1 // posix-threads.cc - interface between libjava and POSIX threads.
   2
   3 /* Copyright (C) 1998, 1999, 2000, 2001  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 #include <gc.h>
  20 #endif /* HAVE_BOEHM_GC */
  21
  22 #include <stdlib.h>
  23 #include <time.h>
  24 #include <signal.h>
  25 #include <errno.h>
  26 #include <limits.h>
  27
  28 #include <gcj/cni.h>
  29 #include <jvm.h>
  30 #include <java/lang/Thread.h>
  31 #include <java/lang/System.h>
  32 #include <java/lang/Long.h>
  33 #include <java/lang/OutOfMemoryError.h>
  34
  35 // This is used to implement thread startup.
  36 struct starter
  37 {
  38   _Jv_ThreadStartFunc *method;
  39   _Jv_Thread_t *data;
  40 };
  41
  42 // This is the key used to map from the POSIX thread value back to the
  43 // Java object representing the thread.  The key is global to all
  44 // threads, so it is ok to make it a global here.
  45 pthread_key_t _Jv_ThreadKey;
  46
  47 // This is the key used to map from the POSIX thread value back to the
  48 // _Jv_Thread_t* representing the thread.
  49 pthread_key_t _Jv_ThreadDataKey;
  50
  51 // We keep a count of all non-daemon threads which are running.  When
  52 // this reaches zero, _Jv_ThreadWait returns.
  53 static pthread_mutex_t daemon_mutex;
  54 static pthread_cond_t daemon_cond;
  55 static int non_daemon_count;
  56
  57 // The signal to use when interrupting a thread.
  58 #ifdef LINUX_THREADS
  59   // LinuxThreads (prior to glibc 2.1) usurps both SIGUSR1 and SIGUSR2.
  60 #  define INTR SIGHUP
  61 #else /* LINUX_THREADS */
  62 #  define INTR SIGUSR2
  63 #endif /* LINUX_THREADS */
  64
  65 //
  66 // These are the flags that can appear in _Jv_Thread_t.
  67 //
  68
  69 // Thread started.
  70 #define FLAG_START   0x01
  71 // Thread is daemon.
  72 #define FLAG_DAEMON  0x02
  73
  74 \f
  75
  76 // Wait for the condition variable "CV" to be notified.
  77 // Return values:
  78 // 0: the condition was notified, or the timeout expired.
  79 // _JV_NOT_OWNER: the thread does not own the mutex "MU".
  80 // _JV_INTERRUPTED: the thread was interrupted. Its interrupted flag is set.
  81 int
  82 _Jv_CondWait (_Jv_ConditionVariable_t *cv, _Jv_Mutex_t *mu,
  83               jlong millis, jint nanos)
  84 {
  85   pthread_t self = pthread_self();
  86   if (mu->owner != self)
  87     return _JV_NOT_OWNER;
  88
  89   struct timespec ts;
  90   jlong m, startTime;
  91
  92   if (millis > 0 || nanos > 0)
  93     {
  94       startTime = java::lang::System::currentTimeMillis();
  95       m = millis + startTime;
  96       ts.tv_sec = m / 1000;
  97       ts.tv_nsec = ((m % 1000) * 1000000) + nanos;
  98     }
  99
 100   _Jv_Thread_t *current = _Jv_ThreadCurrentData ();
 101   java::lang::Thread *current_obj = _Jv_ThreadCurrent ();
 102
 103   pthread_mutex_lock (&current->wait_mutex);
 104
 105   // Now that we hold the wait mutex, check if this thread has been
 106   // interrupted already.
 107   if (current_obj->interrupt_flag)
 108     {
 109       pthread_mutex_unlock (&current->wait_mutex);
 110       return _JV_INTERRUPTED;
 111     }
 112
 113   // Add this thread to the cv's wait set.
 114   current->next = NULL;
 115
 116   if (cv->first == NULL)
 117     cv->first = current;
 118   else
 119     for (_Jv_Thread_t *t = cv->first;; t = t->next)
 120       {
 121         if (t->next == NULL)
 122           {
 123             t->next = current;
 124             break;
 125           }
 126       }
 127
 128   // Record the current lock depth, so it can be restored when we re-aquire it.
 129   int count = mu->count;
 130
 131   // Release the monitor mutex.
 132   mu->count = 0;
 133   mu->owner = 0;
 134   pthread_mutex_unlock (&mu->mutex);
 135
 136   int r = 0;
 137   bool done_sleeping = false;
 138
 139   while (! done_sleeping)
 140     {
 141       if (millis == 0 && nanos == 0)
 142         r = pthread_cond_wait (&current->wait_cond, &current->wait_mutex);
 143       else
 144         r = pthread_cond_timedwait (&current->wait_cond, &current->wait_mutex,
 145                                     &ts);
 146
 147       // In older glibc's (prior to 2.1.3), the cond_wait functions may
 148       // spuriously wake up on a signal. Catch that here.
 149       if (r != EINTR)
 150         done_sleeping = true;
 151     }
 152
 153   // Check for an interrupt *before* releasing the wait mutex.
 154   jboolean interrupted = current_obj->interrupt_flag;
 155
 156   pthread_mutex_unlock (&current->wait_mutex);
 157
 158   //  Reaquire the monitor mutex, and restore the lock count.
 159   pthread_mutex_lock (&mu->mutex);
 160   mu->owner = self;
 161   mu->count = count;
 162
 163   // If we were interrupted, or if a timeout occured, remove ourself from
 164   // the cv wait list now. (If we were notified normally, notify() will have
 165   // already taken care of this)
 166   if (r == ETIMEDOUT || interrupted)
 167     {
 168       _Jv_Thread_t *prev = NULL;
 169       for (_Jv_Thread_t *t = cv->first; t != NULL; t = t->next)
 170         {
 171           if (t == current)
 172             {
 173               if (prev != NULL)
 174                 prev->next = t->next;
 175               else
 176                 cv->first = t->next;
 177               t->next = NULL;
 178               break;
 179             }
 180           prev = t;
 181         }
 182       if (interrupted)
 183         return _JV_INTERRUPTED;
 184     }
 185
 186   return 0;
 187 }
 188
 189 int
 190 _Jv_CondNotify (_Jv_ConditionVariable_t *cv, _Jv_Mutex_t *mu)
 191 {
 192   if (_Jv_PthreadCheckMonitor (mu))
 193     return _JV_NOT_OWNER;
 194
 195   _Jv_Thread_t *target;
 196   _Jv_Thread_t *prev = NULL;
 197
 198   for (target = cv->first; target != NULL; target = target->next)
 199     {
 200       pthread_mutex_lock (&target->wait_mutex);
 201
 202       if (target->thread_obj->interrupt_flag)
 203         {
 204           // Don't notify a thread that has already been interrupted.
 205           pthread_mutex_unlock (&target->wait_mutex);
 206           prev = target;
 207           continue;
 208         }
 209
 210       pthread_cond_signal (&target->wait_cond);
 211       pthread_mutex_unlock (&target->wait_mutex);
 212
 213       // Two concurrent notify() calls must not be delivered to the same
 214       // thread, so remove the target thread from the cv wait list now.
 215       if (prev == NULL)
 216         cv->first = target->next;
 217       else
 218         prev->next = target->next;
 219
 220       target->next = NULL;
 221
 222       break;
 223     }
 224
 225   return 0;
 226 }
 227
 228 int
 229 _Jv_CondNotifyAll (_Jv_ConditionVariable_t *cv, _Jv_Mutex_t *mu)
 230 {
 231   if (_Jv_PthreadCheckMonitor (mu))
 232     return _JV_NOT_OWNER;
 233
 234   _Jv_Thread_t *target;
 235   _Jv_Thread_t *prev = NULL;
 236
 237   for (target = cv->first; target != NULL; target = target->next)
 238     {
 239       pthread_mutex_lock (&target->wait_mutex);
 240       pthread_cond_signal (&target->wait_cond);
 241       pthread_mutex_unlock (&target->wait_mutex);
 242
 243       if (prev != NULL)
 244         prev->next = NULL;
 245       prev = target;
 246     }
 247   if (prev != NULL)
 248     prev->next = NULL;
 249
 250   cv->first = NULL;
 251
 252   return 0;
 253 }
 254
 255 void
 256 _Jv_ThreadInterrupt (_Jv_Thread_t *data)
 257 {
 258   pthread_mutex_lock (&data->wait_mutex);
 259
 260   // Set the thread's interrupted flag *after* aquiring its wait_mutex. This
 261   // ensures that there are no races with the interrupt flag being set after
 262   // the waiting thread checks it and before pthread_cond_wait is entered.
 263   data->thread_obj->interrupt_flag = true;
 264
 265   // Interrupt blocking system calls using a signal.
 266 //  pthread_kill (data->thread, INTR);
 267
 268   pthread_cond_signal (&data->wait_cond);
 269
 270   pthread_mutex_unlock (&data->wait_mutex);
 271 }
 272
 273 static void
 274 handle_intr (int)
 275 {
 276   // Do nothing.
 277 }
 278
 279 void
 280 _Jv_InitThreads (void)
 281 {
 282   pthread_key_create (&_Jv_ThreadKey, NULL);
 283   pthread_key_create (&_Jv_ThreadDataKey, NULL);
 284   pthread_mutex_init (&daemon_mutex, NULL);
 285   pthread_cond_init (&daemon_cond, 0);
 286   non_daemon_count = 0;
 287
 288   // Arrange for the interrupt signal to interrupt system calls.
 289   struct sigaction act;
 290   act.sa_handler = handle_intr;
 291   sigemptyset (&act.sa_mask);
 292   act.sa_flags = 0;
 293   sigaction (INTR, &act, NULL);
 294 }
 295
 296 _Jv_Thread_t *
 297 _Jv_ThreadInitData (java::lang::Thread *obj)
 298 {
 299   _Jv_Thread_t *data = (_Jv_Thread_t *) _Jv_Malloc (sizeof (_Jv_Thread_t));
 300   data->flags = 0;
 301   data->thread_obj = obj;
 302
 303   pthread_mutex_init (&data->wait_mutex, NULL);
 304   pthread_cond_init (&data->wait_cond, NULL);
 305
 306   return data;
 307 }
 308
 309 void
 310 _Jv_ThreadDestroyData (_Jv_Thread_t *data)
 311 {
 312   pthread_mutex_destroy (&data->wait_mutex);
 313   pthread_cond_destroy (&data->wait_cond);
 314   _Jv_Free ((void *)data);
 315 }
 316
 317 void
 318 _Jv_ThreadSetPriority (_Jv_Thread_t *data, jint prio)
 319 {
 320   if (data->flags & FLAG_START)
 321     {
 322       struct sched_param param;
 323
 324       param.sched_priority = prio;
 325       pthread_setschedparam (data->thread, SCHED_RR, &param);
 326     }
 327 }
 328
 329 void
 330 _Jv_ThreadRegister (_Jv_Thread_t *data)
 331 {
 332   pthread_setspecific (_Jv_ThreadKey, data->thread_obj);
 333   pthread_setspecific (_Jv_ThreadDataKey, data);
 334
 335   // glibc 2.1.3 doesn't set the value of `thread' until after start_routine
 336   // is called. Since it may need to be accessed from the new thread, work
 337   // around the potential race here by explicitly setting it again.
 338   data->thread = pthread_self ();
 339
 340 # ifdef SLOW_PTHREAD_SELF
 341     // Clear all self cache slots that might be needed by this thread.
 342     int dummy;
 343     int low_index = SC_INDEX(&dummy) + SC_CLEAR_MIN;
 344     int high_index = SC_INDEX(&dummy) + SC_CLEAR_MAX;
 345     for (int i = low_index; i <= high_index; ++i)
 346       {
 347         int current_index = i;
 348         if (current_index < 0)
 349           current_index += SELF_CACHE_SIZE;
 350         if (current_index >= SELF_CACHE_SIZE)
 351           current_index -= SELF_CACHE_SIZE;
 352         _Jv_self_cache[current_index].high_sp_bits = BAD_HIGH_SP_VALUE;
 353       }
 354 # endif
 355 }
 356
 357 void
 358 _Jv_ThreadUnRegister ()
 359 {
 360   pthread_setspecific (_Jv_ThreadKey, NULL);
 361   pthread_setspecific (_Jv_ThreadDataKey, NULL);
 362 }
 363
 364 // This function is called when a thread is started.  We don't arrange
 365 // to call the `run' method directly, because this function must
 366 // return a value.
 367 static void *
 368 really_start (void *x)
 369 {
 370   struct starter *info = (struct starter *) x;
 371
 372   _Jv_ThreadRegister (info->data);
 373
 374   info->method (info->data->thread_obj);
 375
 376   if (! (info->data->flags & FLAG_DAEMON))
 377     {
 378       pthread_mutex_lock (&daemon_mutex);
 379       --non_daemon_count;
 380       if (! non_daemon_count)
 381         pthread_cond_signal (&daemon_cond);
 382       pthread_mutex_unlock (&daemon_mutex);
 383     }
 384
 385   return NULL;
 386 }
 387
 388 void
 389 _Jv_ThreadStart (java::lang::Thread *thread, _Jv_Thread_t *data,
 390                  _Jv_ThreadStartFunc *meth)
 391 {
 392   struct sched_param param;
 393   pthread_attr_t attr;
 394   struct starter *info;
 395
 396   if (data->flags & FLAG_START)
 397     return;
 398   data->flags |= FLAG_START;
 399
 400   param.sched_priority = thread->getPriority();
 401
 402   pthread_attr_init (&attr);
 403   pthread_attr_setschedparam (&attr, &param);
 404   pthread_attr_setdetachstate (&attr, PTHREAD_CREATE_DETACHED);
 405
 406   info = (struct starter *) _Jv_AllocBytes (sizeof (struct starter));
 407   info->method = meth;
 408   info->data = data;
 409
 410   if (! thread->isDaemon())
 411     {
 412       pthread_mutex_lock (&daemon_mutex);
 413       ++non_daemon_count;
 414       pthread_mutex_unlock (&daemon_mutex);
 415     }
 416   else
 417     data->flags |= FLAG_DAEMON;
 418   int r = pthread_create (&data->thread, &attr, really_start, (void *) info);
 419
 420   pthread_attr_destroy (&attr);
 421
 422   if (r)
 423     {
 424       const char* msg = "Cannot create additional threads";
 425       throw new java::lang::OutOfMemoryError (JvNewStringUTF (msg));
 426     }
 427 }
 428
 429 void
 430 _Jv_ThreadWait (void)
 431 {
 432   pthread_mutex_lock (&daemon_mutex);
 433   if (non_daemon_count)
 434     pthread_cond_wait (&daemon_cond, &daemon_mutex);
 435   pthread_mutex_unlock (&daemon_mutex);
 436 }
 437
 438 #if defined(SLOW_PTHREAD_SELF)
 439
 440 // Support for pthread_self() lookup cache.
 441
 442 volatile self_cache_entry _Jv_self_cache[SELF_CACHE_SIZE];
 443
 444
 445 _Jv_ThreadId_t
 446 _Jv_ThreadSelf_out_of_line(volatile self_cache_entry *sce, size_t high_sp_bits)
 447 {
 448   pthread_t self = pthread_self();
 449   // The ordering between the following writes matters.
 450   // On Alpha, we probably need a memory barrier in the middle.
 451   sce -> high_sp_bits = high_sp_bits;
 452   sce -> self = self;
 453   return self;
 454 }
 455
 456 #endif /* SLOW_PTHREAD_SELF */