libjava/posix-threads.cc

   1 // posix-threads.cc - interface between libjava and POSIX threads.
   2
   3 /* Copyright (C) 1998, 1999, 2000, 2001, 2004  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 #ifdef HAVE_UNISTD_H
  28 #include <unistd.h>     // To test for _POSIX_THREAD_PRIORITY_SCHEDULING
  29 #endif
  30
  31 #include <gcj/cni.h>
  32 #include <jvm.h>
  33 #include <java/lang/Thread.h>
  34 #include <java/lang/System.h>
  35 #include <java/lang/Long.h>
  36 #include <java/lang/OutOfMemoryError.h>
  37 #include <java/lang/InternalError.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 #if defined(LINUX_THREADS) || defined(FREEBSD_THREADS)
  63   // LinuxThreads (prior to glibc 2.1) usurps both SIGUSR1 and SIGUSR2.
  64   // GC on FreeBSD uses both SIGUSR1 and SIGUSR2.
  65 #  define INTR SIGHUP
  66 #else /* LINUX_THREADS */
  67 #  define INTR SIGUSR2
  68 #endif /* LINUX_THREADS */
  69
  70 //
  71 // These are the flags that can appear in _Jv_Thread_t.
  72 //
  73
  74 // Thread started.
  75 #define FLAG_START   0x01
  76 // Thread is daemon.
  77 #define FLAG_DAEMON  0x02
  78
  79 \f
  80
  81 // Wait for the condition variable "CV" to be notified.
  82 // Return values:
  83 // 0: the condition was notified, or the timeout expired.
  84 // _JV_NOT_OWNER: the thread does not own the mutex "MU".
  85 // _JV_INTERRUPTED: the thread was interrupted. Its interrupted flag is set.
  86 int
  87 _Jv_CondWait (_Jv_ConditionVariable_t *cv, _Jv_Mutex_t *mu,
  88               jlong millis, jint nanos)
  89 {
  90   pthread_t self = pthread_self();
  91   if (mu->owner != self)
  92     return _JV_NOT_OWNER;
  93
  94   struct timespec ts;
  95   jlong m, startTime;
  96
  97   if (millis > 0 || nanos > 0)
  98     {
  99       startTime = java::lang::System::currentTimeMillis();
 100       m = millis + startTime;
 101       ts.tv_sec = m / 1000;
 102       ts.tv_nsec = ((m % 1000) * 1000000) + nanos;
 103     }
 104
 105   _Jv_Thread_t *current = _Jv_ThreadCurrentData ();
 106   java::lang::Thread *current_obj = _Jv_ThreadCurrent ();
 107
 108   pthread_mutex_lock (&current->wait_mutex);
 109
 110   // Now that we hold the wait mutex, check if this thread has been
 111   // interrupted already.
 112   if (current_obj->interrupt_flag)
 113     {
 114       pthread_mutex_unlock (&current->wait_mutex);
 115       return _JV_INTERRUPTED;
 116     }
 117
 118   // Add this thread to the cv's wait set.
 119   current->next = NULL;
 120
 121   if (cv->first == NULL)
 122     cv->first = current;
 123   else
 124     for (_Jv_Thread_t *t = cv->first;; t = t->next)
 125       {
 126         if (t->next == NULL)
 127           {
 128             t->next = current;
 129             break;
 130           }
 131       }
 132
 133   // Record the current lock depth, so it can be restored when we re-aquire it.
 134   int count = mu->count;
 135
 136   // Release the monitor mutex.
 137   mu->count = 0;
 138   mu->owner = 0;
 139   pthread_mutex_unlock (&mu->mutex);
 140
 141   int r = 0;
 142   bool done_sleeping = false;
 143
 144   while (! done_sleeping)
 145     {
 146       if (millis == 0 && nanos == 0)
 147         r = pthread_cond_wait (&current->wait_cond, &current->wait_mutex);
 148       else
 149         r = pthread_cond_timedwait (&current->wait_cond, &current->wait_mutex,
 150                                     &ts);
 151
 152       // In older glibc's (prior to 2.1.3), the cond_wait functions may
 153       // spuriously wake up on a signal. Catch that here.
 154       if (r != EINTR)
 155         done_sleeping = true;
 156     }
 157
 158   // Check for an interrupt *before* releasing the wait mutex.
 159   jboolean interrupted = current_obj->interrupt_flag;
 160
 161   pthread_mutex_unlock (&current->wait_mutex);
 162
 163   //  Reaquire the monitor mutex, and restore the lock count.
 164   pthread_mutex_lock (&mu->mutex);
 165   mu->owner = self;
 166   mu->count = count;
 167
 168   // If we were interrupted, or if a timeout occurred, remove ourself from
 169   // the cv wait list now. (If we were notified normally, notify() will have
 170   // already taken care of this)
 171   if (r == ETIMEDOUT || interrupted)
 172     {
 173       _Jv_Thread_t *prev = NULL;
 174       for (_Jv_Thread_t *t = cv->first; t != NULL; t = t->next)
 175         {
 176           if (t == current)
 177             {
 178               if (prev != NULL)
 179                 prev->next = t->next;
 180               else
 181                 cv->first = t->next;
 182               t->next = NULL;
 183               break;
 184             }
 185           prev = t;
 186         }
 187       if (interrupted)
 188         return _JV_INTERRUPTED;
 189     }
 190
 191   return 0;
 192 }
 193
 194 int
 195 _Jv_CondNotify (_Jv_ConditionVariable_t *cv, _Jv_Mutex_t *mu)
 196 {
 197   if (_Jv_MutexCheckMonitor (mu))
 198     return _JV_NOT_OWNER;
 199
 200   _Jv_Thread_t *target;
 201   _Jv_Thread_t *prev = NULL;
 202
 203   for (target = cv->first; target != NULL; target = target->next)
 204     {
 205       pthread_mutex_lock (&target->wait_mutex);
 206
 207       if (target->thread_obj->interrupt_flag)
 208         {
 209           // Don't notify a thread that has already been interrupted.
 210           pthread_mutex_unlock (&target->wait_mutex);
 211           prev = target;
 212           continue;
 213         }
 214
 215       pthread_cond_signal (&target->wait_cond);
 216       pthread_mutex_unlock (&target->wait_mutex);
 217
 218       // Two concurrent notify() calls must not be delivered to the same
 219       // thread, so remove the target thread from the cv wait list now.
 220       if (prev == NULL)
 221         cv->first = target->next;
 222       else
 223         prev->next = target->next;
 224
 225       target->next = NULL;
 226
 227       break;
 228     }
 229
 230   return 0;
 231 }
 232
 233 int
 234 _Jv_CondNotifyAll (_Jv_ConditionVariable_t *cv, _Jv_Mutex_t *mu)
 235 {
 236   if (_Jv_MutexCheckMonitor (mu))
 237     return _JV_NOT_OWNER;
 238
 239   _Jv_Thread_t *target;
 240   _Jv_Thread_t *prev = NULL;
 241
 242   for (target = cv->first; target != NULL; target = target->next)
 243     {
 244       pthread_mutex_lock (&target->wait_mutex);
 245       pthread_cond_signal (&target->wait_cond);
 246       pthread_mutex_unlock (&target->wait_mutex);
 247
 248       if (prev != NULL)
 249         prev->next = NULL;
 250       prev = target;
 251     }
 252   if (prev != NULL)
 253     prev->next = NULL;
 254
 255   cv->first = NULL;
 256
 257   return 0;
 258 }
 259
 260 void
 261 _Jv_ThreadInterrupt (_Jv_Thread_t *data)
 262 {
 263   pthread_mutex_lock (&data->wait_mutex);
 264
 265   // Set the thread's interrupted flag *after* aquiring its wait_mutex. This
 266   // ensures that there are no races with the interrupt flag being set after
 267   // the waiting thread checks it and before pthread_cond_wait is entered.
 268   data->thread_obj->interrupt_flag = true;
 269
 270   // Interrupt blocking system calls using a signal.
 271   pthread_kill (data->thread, INTR);
 272
 273   pthread_cond_signal (&data->wait_cond);
 274
 275   pthread_mutex_unlock (&data->wait_mutex);
 276 }
 277
 278 static void
 279 handle_intr (int)
 280 {
 281   // Do nothing.
 282 }
 283
 284 void
 285 _Jv_InitThreads (void)
 286 {
 287   pthread_key_create (&_Jv_ThreadKey, NULL);
 288   pthread_key_create (&_Jv_ThreadDataKey, NULL);
 289   pthread_mutex_init (&daemon_mutex, NULL);
 290   pthread_cond_init (&daemon_cond, 0);
 291   non_daemon_count = 0;
 292
 293   // Arrange for the interrupt signal to interrupt system calls.
 294   struct sigaction act;
 295   act.sa_handler = handle_intr;
 296   sigemptyset (&act.sa_mask);
 297   act.sa_flags = 0;
 298   sigaction (INTR, &act, NULL);
 299 }
 300
 301 _Jv_Thread_t *
 302 _Jv_ThreadInitData (java::lang::Thread *obj)
 303 {
 304   _Jv_Thread_t *data = (_Jv_Thread_t *) _Jv_Malloc (sizeof (_Jv_Thread_t));
 305   data->flags = 0;
 306   data->thread_obj = obj;
 307
 308   pthread_mutex_init (&data->wait_mutex, NULL);
 309   pthread_cond_init (&data->wait_cond, NULL);
 310
 311   return data;
 312 }
 313
 314 void
 315 _Jv_ThreadDestroyData (_Jv_Thread_t *data)
 316 {
 317   pthread_mutex_destroy (&data->wait_mutex);
 318   pthread_cond_destroy (&data->wait_cond);
 319   _Jv_Free ((void *)data);
 320 }
 321
 322 void
 323 _Jv_ThreadSetPriority (_Jv_Thread_t *data, jint prio)
 324 {
 325 #ifdef _POSIX_THREAD_PRIORITY_SCHEDULING
 326   if (data->flags & FLAG_START)
 327     {
 328       struct sched_param param;
 329
 330       param.sched_priority = prio;
 331       pthread_setschedparam (data->thread, SCHED_RR, &param);
 332     }
 333 #endif
 334 }
 335
 336 static void
 337 block_sigchld()
 338 {
 339   sigset_t mask;
 340   sigemptyset (&mask);
 341   sigaddset (&mask, SIGCHLD);
 342   int c = pthread_sigmask (SIG_BLOCK, &mask, NULL);
 343   if (c != 0)
 344     throw new java::lang::InternalError (JvNewStringUTF (strerror (c)));
 345 }
 346
 347 void
 348 _Jv_ThreadRegister (_Jv_Thread_t *data)
 349 {
 350   pthread_setspecific (_Jv_ThreadKey, data->thread_obj);
 351   pthread_setspecific (_Jv_ThreadDataKey, data);
 352
 353   // glibc 2.1.3 doesn't set the value of `thread' until after start_routine
 354   // is called. Since it may need to be accessed from the new thread, work
 355   // around the potential race here by explicitly setting it again.
 356   data->thread = pthread_self ();
 357
 358 # ifdef SLOW_PTHREAD_SELF
 359     // Clear all self cache slots that might be needed by this thread.
 360     int dummy;
 361     int low_index = SC_INDEX(&dummy) + SC_CLEAR_MIN;
 362     int high_index = SC_INDEX(&dummy) + SC_CLEAR_MAX;
 363     for (int i = low_index; i <= high_index; ++i)
 364       {
 365         int current_index = i;
 366         if (current_index < 0)
 367           current_index += SELF_CACHE_SIZE;
 368         if (current_index >= SELF_CACHE_SIZE)
 369           current_index -= SELF_CACHE_SIZE;
 370         _Jv_self_cache[current_index].high_sp_bits = BAD_HIGH_SP_VALUE;
 371       }
 372 # endif
 373   // Block SIGCHLD which is used in natPosixProcess.cc.
 374   block_sigchld();
 375 }
 376
 377 void
 378 _Jv_ThreadUnRegister ()
 379 {
 380   pthread_setspecific (_Jv_ThreadKey, NULL);
 381   pthread_setspecific (_Jv_ThreadDataKey, NULL);
 382 }
 383
 384 // This function is called when a thread is started.  We don't arrange
 385 // to call the `run' method directly, because this function must
 386 // return a value.
 387 static void *
 388 really_start (void *x)
 389 {
 390   struct starter *info = (struct starter *) x;
 391
 392   _Jv_ThreadRegister (info->data);
 393
 394   info->method (info->data->thread_obj);
 395
 396   if (! (info->data->flags & FLAG_DAEMON))
 397     {
 398       pthread_mutex_lock (&daemon_mutex);
 399       --non_daemon_count;
 400       if (! non_daemon_count)
 401         pthread_cond_signal (&daemon_cond);
 402       pthread_mutex_unlock (&daemon_mutex);
 403     }
 404
 405   return NULL;
 406 }
 407
 408 void
 409 _Jv_ThreadStart (java::lang::Thread *thread, _Jv_Thread_t *data,
 410                  _Jv_ThreadStartFunc *meth)
 411 {
 412   struct sched_param param;
 413   pthread_attr_t attr;
 414   struct starter *info;
 415
 416   if (data->flags & FLAG_START)
 417     return;
 418   data->flags |= FLAG_START;
 419
 420   // Block SIGCHLD which is used in natPosixProcess.cc.
 421   // The current mask is inherited by the child thread.
 422   block_sigchld();
 423
 424   param.sched_priority = thread->getPriority();
 425
 426   pthread_attr_init (&attr);
 427   pthread_attr_setschedparam (&attr, &param);
 428   pthread_attr_setdetachstate (&attr, PTHREAD_CREATE_DETACHED);
 429
 430   info = (struct starter *) _Jv_AllocBytes (sizeof (struct starter));
 431   info->method = meth;
 432   info->data = data;
 433
 434   if (! thread->isDaemon())
 435     {
 436       pthread_mutex_lock (&daemon_mutex);
 437       ++non_daemon_count;
 438       pthread_mutex_unlock (&daemon_mutex);
 439     }
 440   else
 441     data->flags |= FLAG_DAEMON;
 442   int r = pthread_create (&data->thread, &attr, really_start, (void *) info);
 443
 444   pthread_attr_destroy (&attr);
 445
 446   if (r)
 447     {
 448       const char* msg = "Cannot create additional threads";
 449       throw new java::lang::OutOfMemoryError (JvNewStringUTF (msg));
 450     }
 451 }
 452
 453 void
 454 _Jv_ThreadWait (void)
 455 {
 456   pthread_mutex_lock (&daemon_mutex);
 457   if (non_daemon_count)
 458     pthread_cond_wait (&daemon_cond, &daemon_mutex);
 459   pthread_mutex_unlock (&daemon_mutex);
 460 }
 461
 462 #if defined(SLOW_PTHREAD_SELF)
 463
 464 #include "sysdep/locks.h"
 465
 466 // Support for pthread_self() lookup cache.
 467 volatile self_cache_entry _Jv_self_cache[SELF_CACHE_SIZE];
 468
 469 _Jv_ThreadId_t
 470 _Jv_ThreadSelf_out_of_line(volatile self_cache_entry *sce, size_t high_sp_bits)
 471 {
 472   pthread_t self = pthread_self();
 473   sce -> high_sp_bits = high_sp_bits;
 474   write_barrier();
 475   sce -> self = self;
 476   return self;
 477 }
 478
 479 #endif /* SLOW_PTHREAD_SELF */