1 /* Locking in multithreaded situations.
2 Copyright (C) 2005-2006 Free Software Foundation, Inc.
4 This program is free software; you can redistribute it and/or modify it
5 under the terms of the GNU Library General Public License as published
6 by the Free Software Foundation; either version 2, or (at your option)
9 This program is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 Library General Public License for more details.
14 You should have received a copy of the GNU Library General Public
15 License along with this program; if not, write to the Free Software
16 Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
19 /* Written by Bruno Haible <bruno@clisp.org>, 2005.
20 Based on GCC's gthr-posix.h, gthr-posix95.h, gthr-solaris.h,
27 /* ========================================================================= */
31 /* Use the POSIX threads library. */
33 # if PTHREAD_IN_USE_DETECTION_HARD
35 /* The function to be executed by a dummy thread. */
37 dummy_thread_func (void *arg)
43 glthread_in_use (void)
46 static int result; /* 1: linked with -lpthread, 0: only with libc */
52 if (pthread_create (&thread, NULL, dummy_thread_func, NULL) != 0)
53 /* Thread creation failed. */
57 /* Thread creation works. */
59 if (pthread_join (thread, &retval) != 0)
70 /* -------------------------- gl_lock_t datatype -------------------------- */
72 /* ------------------------- gl_rwlock_t datatype ------------------------- */
74 # if HAVE_PTHREAD_RWLOCK
76 # if !defined PTHREAD_RWLOCK_INITIALIZER
79 glthread_rwlock_init (gl_rwlock_t *lock)
81 if (pthread_rwlock_init (&lock->rwlock, NULL) != 0)
83 lock->initialized = 1;
87 glthread_rwlock_rdlock (gl_rwlock_t *lock)
89 if (!lock->initialized)
91 if (pthread_mutex_lock (&lock->guard) != 0)
93 if (!lock->initialized)
94 glthread_rwlock_init (lock);
95 if (pthread_mutex_unlock (&lock->guard) != 0)
98 if (pthread_rwlock_rdlock (&lock->rwlock) != 0)
103 glthread_rwlock_wrlock (gl_rwlock_t *lock)
105 if (!lock->initialized)
107 if (pthread_mutex_lock (&lock->guard) != 0)
109 if (!lock->initialized)
110 glthread_rwlock_init (lock);
111 if (pthread_mutex_unlock (&lock->guard) != 0)
114 if (pthread_rwlock_wrlock (&lock->rwlock) != 0)
119 glthread_rwlock_unlock (gl_rwlock_t *lock)
121 if (!lock->initialized)
123 if (pthread_rwlock_unlock (&lock->rwlock) != 0)
128 glthread_rwlock_destroy (gl_rwlock_t *lock)
130 if (!lock->initialized)
132 if (pthread_rwlock_destroy (&lock->rwlock) != 0)
134 lock->initialized = 0;
142 glthread_rwlock_init (gl_rwlock_t *lock)
144 if (pthread_mutex_init (&lock->lock, NULL) != 0)
146 if (pthread_cond_init (&lock->waiting_readers, NULL) != 0)
148 if (pthread_cond_init (&lock->waiting_writers, NULL) != 0)
150 lock->waiting_writers_count = 0;
155 glthread_rwlock_rdlock (gl_rwlock_t *lock)
157 if (pthread_mutex_lock (&lock->lock) != 0)
159 /* Test whether only readers are currently running, and whether the runcount
160 field will not overflow. */
161 /* POSIX says: "It is implementation-defined whether the calling thread
162 acquires the lock when a writer does not hold the lock and there are
163 writers blocked on the lock." Let's say, no: give the writers a higher
165 while (!(lock->runcount + 1 > 0 && lock->waiting_writers_count == 0))
167 /* This thread has to wait for a while. Enqueue it among the
169 if (pthread_cond_wait (&lock->waiting_readers, &lock->lock) != 0)
173 if (pthread_mutex_unlock (&lock->lock) != 0)
178 glthread_rwlock_wrlock (gl_rwlock_t *lock)
180 if (pthread_mutex_lock (&lock->lock) != 0)
182 /* Test whether no readers or writers are currently running. */
183 while (!(lock->runcount == 0))
185 /* This thread has to wait for a while. Enqueue it among the
187 lock->waiting_writers_count++;
188 if (pthread_cond_wait (&lock->waiting_writers, &lock->lock) != 0)
190 lock->waiting_writers_count--;
192 lock->runcount--; /* runcount becomes -1 */
193 if (pthread_mutex_unlock (&lock->lock) != 0)
198 glthread_rwlock_unlock (gl_rwlock_t *lock)
200 if (pthread_mutex_lock (&lock->lock) != 0)
202 if (lock->runcount < 0)
204 /* Drop a writer lock. */
205 if (!(lock->runcount == -1))
211 /* Drop a reader lock. */
212 if (!(lock->runcount > 0))
216 if (lock->runcount == 0)
218 /* POSIX recommends that "write locks shall take precedence over read
219 locks", to avoid "writer starvation". */
220 if (lock->waiting_writers_count > 0)
222 /* Wake up one of the waiting writers. */
223 if (pthread_cond_signal (&lock->waiting_writers) != 0)
228 /* Wake up all waiting readers. */
229 if (pthread_cond_broadcast (&lock->waiting_readers) != 0)
233 if (pthread_mutex_unlock (&lock->lock) != 0)
238 glthread_rwlock_destroy (gl_rwlock_t *lock)
240 if (pthread_mutex_destroy (&lock->lock) != 0)
242 if (pthread_cond_destroy (&lock->waiting_readers) != 0)
244 if (pthread_cond_destroy (&lock->waiting_writers) != 0)
250 /* --------------------- gl_recursive_lock_t datatype --------------------- */
252 # if HAVE_PTHREAD_MUTEX_RECURSIVE
254 # if !(defined PTHREAD_RECURSIVE_MUTEX_INITIALIZER || defined PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP)
257 glthread_recursive_lock_init (gl_recursive_lock_t *lock)
259 pthread_mutexattr_t attributes;
261 if (pthread_mutexattr_init (&attributes) != 0)
263 if (pthread_mutexattr_settype (&attributes, PTHREAD_MUTEX_RECURSIVE) != 0)
265 if (pthread_mutex_init (&lock->recmutex, &attributes) != 0)
267 if (pthread_mutexattr_destroy (&attributes) != 0)
269 lock->initialized = 1;
273 glthread_recursive_lock_lock (gl_recursive_lock_t *lock)
275 if (!lock->initialized)
277 if (pthread_mutex_lock (&lock->guard) != 0)
279 if (!lock->initialized)
280 glthread_recursive_lock_init (lock);
281 if (pthread_mutex_unlock (&lock->guard) != 0)
284 if (pthread_mutex_lock (&lock->recmutex) != 0)
289 glthread_recursive_lock_unlock (gl_recursive_lock_t *lock)
291 if (!lock->initialized)
293 if (pthread_mutex_unlock (&lock->recmutex) != 0)
298 glthread_recursive_lock_destroy (gl_recursive_lock_t *lock)
300 if (!lock->initialized)
302 if (pthread_mutex_destroy (&lock->recmutex) != 0)
304 lock->initialized = 0;
312 glthread_recursive_lock_init (gl_recursive_lock_t *lock)
314 if (pthread_mutex_init (&lock->mutex, NULL) != 0)
316 lock->owner = (pthread_t) 0;
321 glthread_recursive_lock_lock (gl_recursive_lock_t *lock)
323 pthread_t self = pthread_self ();
324 if (lock->owner != self)
326 if (pthread_mutex_lock (&lock->mutex) != 0)
330 if (++(lock->depth) == 0) /* wraparound? */
335 glthread_recursive_lock_unlock (gl_recursive_lock_t *lock)
337 if (lock->owner != pthread_self ())
339 if (lock->depth == 0)
341 if (--(lock->depth) == 0)
343 lock->owner = (pthread_t) 0;
344 if (pthread_mutex_unlock (&lock->mutex) != 0)
350 glthread_recursive_lock_destroy (gl_recursive_lock_t *lock)
352 if (lock->owner != (pthread_t) 0)
354 if (pthread_mutex_destroy (&lock->mutex) != 0)
360 /* -------------------------- gl_once_t datatype -------------------------- */
362 static const pthread_once_t fresh_once = PTHREAD_ONCE_INIT;
365 glthread_once_singlethreaded (pthread_once_t *once_control)
367 /* We don't know whether pthread_once_t is an integer type, a floating-point
368 type, a pointer type, or a structure type. */
369 char *firstbyte = (char *)once_control;
370 if (*firstbyte == *(const char *)&fresh_once)
372 /* First time use of once_control. Invert the first byte. */
373 *firstbyte = ~ *(const char *)&fresh_once;
382 /* ========================================================================= */
386 /* Use the GNU Pth threads library. */
388 /* -------------------------- gl_lock_t datatype -------------------------- */
390 /* ------------------------- gl_rwlock_t datatype ------------------------- */
392 /* --------------------- gl_recursive_lock_t datatype --------------------- */
394 /* -------------------------- gl_once_t datatype -------------------------- */
397 glthread_once_call (void *arg)
399 void (**gl_once_temp_addr) (void) = (void (**) (void)) arg;
400 void (*initfunction) (void) = *gl_once_temp_addr;
405 glthread_once_singlethreaded (pth_once_t *once_control)
407 /* We know that pth_once_t is an integer type. */
408 if (*once_control == PTH_ONCE_INIT)
410 /* First time use of once_control. Invert the marker. */
411 *once_control = ~ PTH_ONCE_INIT;
420 /* ========================================================================= */
422 #if USE_SOLARIS_THREADS
424 /* Use the old Solaris threads library. */
426 /* -------------------------- gl_lock_t datatype -------------------------- */
428 /* ------------------------- gl_rwlock_t datatype ------------------------- */
430 /* --------------------- gl_recursive_lock_t datatype --------------------- */
433 glthread_recursive_lock_init (gl_recursive_lock_t *lock)
435 if (mutex_init (&lock->mutex, USYNC_THREAD, NULL) != 0)
437 lock->owner = (thread_t) 0;
442 glthread_recursive_lock_lock (gl_recursive_lock_t *lock)
444 thread_t self = thr_self ();
445 if (lock->owner != self)
447 if (mutex_lock (&lock->mutex) != 0)
451 if (++(lock->depth) == 0) /* wraparound? */
456 glthread_recursive_lock_unlock (gl_recursive_lock_t *lock)
458 if (lock->owner != thr_self ())
460 if (lock->depth == 0)
462 if (--(lock->depth) == 0)
464 lock->owner = (thread_t) 0;
465 if (mutex_unlock (&lock->mutex) != 0)
471 glthread_recursive_lock_destroy (gl_recursive_lock_t *lock)
473 if (lock->owner != (thread_t) 0)
475 if (mutex_destroy (&lock->mutex) != 0)
479 /* -------------------------- gl_once_t datatype -------------------------- */
482 glthread_once (gl_once_t *once_control, void (*initfunction) (void))
484 if (!once_control->inited)
486 /* Use the mutex to guarantee that if another thread is already calling
487 the initfunction, this thread waits until it's finished. */
488 if (mutex_lock (&once_control->mutex) != 0)
490 if (!once_control->inited)
492 once_control->inited = 1;
495 if (mutex_unlock (&once_control->mutex) != 0)
501 glthread_once_singlethreaded (gl_once_t *once_control)
503 /* We know that gl_once_t contains an integer type. */
504 if (!once_control->inited)
506 /* First time use of once_control. Invert the marker. */
507 once_control->inited = ~ 0;
516 /* ========================================================================= */
518 #if USE_WIN32_THREADS
520 /* -------------------------- gl_lock_t datatype -------------------------- */
523 glthread_lock_init (gl_lock_t *lock)
525 InitializeCriticalSection (&lock->lock);
526 lock->guard.done = 1;
530 glthread_lock_lock (gl_lock_t *lock)
532 if (!lock->guard.done)
534 if (InterlockedIncrement (&lock->guard.started) == 0)
535 /* This thread is the first one to need this lock. Initialize it. */
536 glthread_lock_init (lock);
538 /* Yield the CPU while waiting for another thread to finish
539 initializing this lock. */
540 while (!lock->guard.done)
543 EnterCriticalSection (&lock->lock);
547 glthread_lock_unlock (gl_lock_t *lock)
549 if (!lock->guard.done)
551 LeaveCriticalSection (&lock->lock);
555 glthread_lock_destroy (gl_lock_t *lock)
557 if (!lock->guard.done)
559 DeleteCriticalSection (&lock->lock);
560 lock->guard.done = 0;
563 /* ------------------------- gl_rwlock_t datatype ------------------------- */
566 gl_waitqueue_init (gl_waitqueue_t *wq)
574 /* Enqueues the current thread, represented by an event, in a wait queue.
575 Returns INVALID_HANDLE_VALUE if an allocation failure occurs. */
577 gl_waitqueue_add (gl_waitqueue_t *wq)
582 if (wq->count == wq->alloc)
584 unsigned int new_alloc = 2 * wq->alloc + 1;
586 (HANDLE *) realloc (wq->array, new_alloc * sizeof (HANDLE));
587 if (new_array == NULL)
588 /* No more memory. */
589 return INVALID_HANDLE_VALUE;
590 /* Now is a good opportunity to rotate the array so that its contents
591 starts at offset 0. */
594 unsigned int old_count = wq->count;
595 unsigned int old_alloc = wq->alloc;
596 unsigned int old_offset = wq->offset;
598 if (old_offset + old_count > old_alloc)
600 unsigned int limit = old_offset + old_count - old_alloc;
601 for (i = 0; i < limit; i++)
602 new_array[old_alloc + i] = new_array[i];
604 for (i = 0; i < old_count; i++)
605 new_array[i] = new_array[old_offset + i];
608 wq->array = new_array;
609 wq->alloc = new_alloc;
611 event = CreateEvent (NULL, TRUE, FALSE, NULL);
612 if (event == INVALID_HANDLE_VALUE)
613 /* No way to allocate an event. */
614 return INVALID_HANDLE_VALUE;
615 index = wq->offset + wq->count;
616 if (index >= wq->alloc)
618 wq->array[index] = event;
623 /* Notifies the first thread from a wait queue and dequeues it. */
625 gl_waitqueue_notify_first (gl_waitqueue_t *wq)
627 SetEvent (wq->array[wq->offset + 0]);
630 if (wq->count == 0 || wq->offset == wq->alloc)
634 /* Notifies all threads from a wait queue and dequeues them all. */
636 gl_waitqueue_notify_all (gl_waitqueue_t *wq)
640 for (i = 0; i < wq->count; i++)
642 unsigned int index = wq->offset + i;
643 if (index >= wq->alloc)
645 SetEvent (wq->array[index]);
652 glthread_rwlock_init (gl_rwlock_t *lock)
654 InitializeCriticalSection (&lock->lock);
655 gl_waitqueue_init (&lock->waiting_readers);
656 gl_waitqueue_init (&lock->waiting_writers);
658 lock->guard.done = 1;
662 glthread_rwlock_rdlock (gl_rwlock_t *lock)
664 if (!lock->guard.done)
666 if (InterlockedIncrement (&lock->guard.started) == 0)
667 /* This thread is the first one to need this lock. Initialize it. */
668 glthread_rwlock_init (lock);
670 /* Yield the CPU while waiting for another thread to finish
671 initializing this lock. */
672 while (!lock->guard.done)
675 EnterCriticalSection (&lock->lock);
676 /* Test whether only readers are currently running, and whether the runcount
677 field will not overflow. */
678 if (!(lock->runcount + 1 > 0))
680 /* This thread has to wait for a while. Enqueue it among the
682 HANDLE event = gl_waitqueue_add (&lock->waiting_readers);
683 if (event != INVALID_HANDLE_VALUE)
686 LeaveCriticalSection (&lock->lock);
687 /* Wait until another thread signals this event. */
688 result = WaitForSingleObject (event, INFINITE);
689 if (result == WAIT_FAILED || result == WAIT_TIMEOUT)
692 /* The thread which signalled the event already did the bookkeeping:
693 removed us from the waiting_readers, incremented lock->runcount. */
694 if (!(lock->runcount > 0))
700 /* Allocation failure. Weird. */
703 LeaveCriticalSection (&lock->lock);
705 EnterCriticalSection (&lock->lock);
707 while (!(lock->runcount + 1 > 0));
711 LeaveCriticalSection (&lock->lock);
715 glthread_rwlock_wrlock (gl_rwlock_t *lock)
717 if (!lock->guard.done)
719 if (InterlockedIncrement (&lock->guard.started) == 0)
720 /* This thread is the first one to need this lock. Initialize it. */
721 glthread_rwlock_init (lock);
723 /* Yield the CPU while waiting for another thread to finish
724 initializing this lock. */
725 while (!lock->guard.done)
728 EnterCriticalSection (&lock->lock);
729 /* Test whether no readers or writers are currently running. */
730 if (!(lock->runcount == 0))
732 /* This thread has to wait for a while. Enqueue it among the
734 HANDLE event = gl_waitqueue_add (&lock->waiting_writers);
735 if (event != INVALID_HANDLE_VALUE)
738 LeaveCriticalSection (&lock->lock);
739 /* Wait until another thread signals this event. */
740 result = WaitForSingleObject (event, INFINITE);
741 if (result == WAIT_FAILED || result == WAIT_TIMEOUT)
744 /* The thread which signalled the event already did the bookkeeping:
745 removed us from the waiting_writers, set lock->runcount = -1. */
746 if (!(lock->runcount == -1))
752 /* Allocation failure. Weird. */
755 LeaveCriticalSection (&lock->lock);
757 EnterCriticalSection (&lock->lock);
759 while (!(lock->runcount == 0));
762 lock->runcount--; /* runcount becomes -1 */
763 LeaveCriticalSection (&lock->lock);
767 glthread_rwlock_unlock (gl_rwlock_t *lock)
769 if (!lock->guard.done)
771 EnterCriticalSection (&lock->lock);
772 if (lock->runcount < 0)
774 /* Drop a writer lock. */
775 if (!(lock->runcount == -1))
781 /* Drop a reader lock. */
782 if (!(lock->runcount > 0))
786 if (lock->runcount == 0)
788 /* POSIX recommends that "write locks shall take precedence over read
789 locks", to avoid "writer starvation". */
790 if (lock->waiting_writers.count > 0)
792 /* Wake up one of the waiting writers. */
794 gl_waitqueue_notify_first (&lock->waiting_writers);
798 /* Wake up all waiting readers. */
799 lock->runcount += lock->waiting_readers.count;
800 gl_waitqueue_notify_all (&lock->waiting_readers);
803 LeaveCriticalSection (&lock->lock);
807 glthread_rwlock_destroy (gl_rwlock_t *lock)
809 if (!lock->guard.done)
811 if (lock->runcount != 0)
813 DeleteCriticalSection (&lock->lock);
814 if (lock->waiting_readers.array != NULL)
815 free (lock->waiting_readers.array);
816 if (lock->waiting_writers.array != NULL)
817 free (lock->waiting_writers.array);
818 lock->guard.done = 0;
821 /* --------------------- gl_recursive_lock_t datatype --------------------- */
824 glthread_recursive_lock_init (gl_recursive_lock_t *lock)
828 InitializeCriticalSection (&lock->lock);
829 lock->guard.done = 1;
833 glthread_recursive_lock_lock (gl_recursive_lock_t *lock)
835 if (!lock->guard.done)
837 if (InterlockedIncrement (&lock->guard.started) == 0)
838 /* This thread is the first one to need this lock. Initialize it. */
839 glthread_recursive_lock_init (lock);
841 /* Yield the CPU while waiting for another thread to finish
842 initializing this lock. */
843 while (!lock->guard.done)
847 DWORD self = GetCurrentThreadId ();
848 if (lock->owner != self)
850 EnterCriticalSection (&lock->lock);
853 if (++(lock->depth) == 0) /* wraparound? */
859 glthread_recursive_lock_unlock (gl_recursive_lock_t *lock)
861 if (lock->owner != GetCurrentThreadId ())
863 if (lock->depth == 0)
865 if (--(lock->depth) == 0)
868 LeaveCriticalSection (&lock->lock);
873 glthread_recursive_lock_destroy (gl_recursive_lock_t *lock)
875 if (lock->owner != 0)
877 DeleteCriticalSection (&lock->lock);
878 lock->guard.done = 0;
881 /* -------------------------- gl_once_t datatype -------------------------- */
884 glthread_once (gl_once_t *once_control, void (*initfunction) (void))
886 if (once_control->inited <= 0)
888 if (InterlockedIncrement (&once_control->started) == 0)
890 /* This thread is the first one to come to this once_control. */
891 InitializeCriticalSection (&once_control->lock);
892 EnterCriticalSection (&once_control->lock);
893 once_control->inited = 0;
895 once_control->inited = 1;
896 LeaveCriticalSection (&once_control->lock);
900 /* Undo last operation. */
901 InterlockedDecrement (&once_control->started);
902 /* Some other thread has already started the initialization.
903 Yield the CPU while waiting for the other thread to finish
904 initializing and taking the lock. */
905 while (once_control->inited < 0)
907 if (once_control->inited <= 0)
909 /* Take the lock. This blocks until the other thread has
910 finished calling the initfunction. */
911 EnterCriticalSection (&once_control->lock);
912 LeaveCriticalSection (&once_control->lock);
913 if (!(once_control->inited > 0))
922 /* ========================================================================= */