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
5
it under the terms of the GNU General Public License as published by
6
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
12
GNU General Public License for more details.
14
You should have received a copy of the GNU General Public License
15
along with this program; if not, write to the Free Software Foundation,
16
Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
18
/* Written by Bruno Haible <bruno@clisp.org>, 2005.
19
Based on GCC's gthr-posix.h, gthr-posix95.h, gthr-solaris.h,
26
/* ========================================================================= */
30
/* Use the POSIX threads library. */
32
# if PTHREAD_IN_USE_DETECTION_HARD
34
/* The function to be executed by a dummy thread. */
36
dummy_thread_func (void *arg)
42
glthread_in_use (void)
45
static int result; /* 1: linked with -lpthread, 0: only with libc */
51
if (pthread_create (&thread, NULL, dummy_thread_func, NULL) != 0)
52
/* Thread creation failed. */
56
/* Thread creation works. */
58
if (pthread_join (thread, &retval) != 0)
69
/* -------------------------- gl_lock_t datatype -------------------------- */
71
/* ------------------------- gl_rwlock_t datatype ------------------------- */
73
# if HAVE_PTHREAD_RWLOCK
75
# if !defined PTHREAD_RWLOCK_INITIALIZER
78
glthread_rwlock_init (gl_rwlock_t *lock)
80
if (pthread_rwlock_init (&lock->rwlock, NULL) != 0)
82
lock->initialized = 1;
86
glthread_rwlock_rdlock (gl_rwlock_t *lock)
88
if (!lock->initialized)
90
if (pthread_mutex_lock (&lock->guard) != 0)
92
if (!lock->initialized)
93
glthread_rwlock_init (lock);
94
if (pthread_mutex_unlock (&lock->guard) != 0)
97
if (pthread_rwlock_rdlock (&lock->rwlock) != 0)
102
glthread_rwlock_wrlock (gl_rwlock_t *lock)
104
if (!lock->initialized)
106
if (pthread_mutex_lock (&lock->guard) != 0)
108
if (!lock->initialized)
109
glthread_rwlock_init (lock);
110
if (pthread_mutex_unlock (&lock->guard) != 0)
113
if (pthread_rwlock_wrlock (&lock->rwlock) != 0)
118
glthread_rwlock_unlock (gl_rwlock_t *lock)
120
if (!lock->initialized)
122
if (pthread_rwlock_unlock (&lock->rwlock) != 0)
127
glthread_rwlock_destroy (gl_rwlock_t *lock)
129
if (!lock->initialized)
131
if (pthread_rwlock_destroy (&lock->rwlock) != 0)
133
lock->initialized = 0;
141
glthread_rwlock_init (gl_rwlock_t *lock)
143
if (pthread_mutex_init (&lock->lock, NULL) != 0)
145
if (pthread_cond_init (&lock->waiting_readers, NULL) != 0)
147
if (pthread_cond_init (&lock->waiting_writers, NULL) != 0)
149
lock->waiting_writers_count = 0;
154
glthread_rwlock_rdlock (gl_rwlock_t *lock)
156
if (pthread_mutex_lock (&lock->lock) != 0)
158
/* Test whether only readers are currently running, and whether the runcount
159
field will not overflow. */
160
/* POSIX says: "It is implementation-defined whether the calling thread
161
acquires the lock when a writer does not hold the lock and there are
162
writers blocked on the lock." Let's say, no: give the writers a higher
164
while (!(lock->runcount + 1 > 0 && lock->waiting_writers_count == 0))
166
/* This thread has to wait for a while. Enqueue it among the
168
if (pthread_cond_wait (&lock->waiting_readers, &lock->lock) != 0)
172
if (pthread_mutex_unlock (&lock->lock) != 0)
177
glthread_rwlock_wrlock (gl_rwlock_t *lock)
179
if (pthread_mutex_lock (&lock->lock) != 0)
181
/* Test whether no readers or writers are currently running. */
182
while (!(lock->runcount == 0))
184
/* This thread has to wait for a while. Enqueue it among the
186
lock->waiting_writers_count++;
187
if (pthread_cond_wait (&lock->waiting_writers, &lock->lock) != 0)
189
lock->waiting_writers_count--;
191
lock->runcount--; /* runcount becomes -1 */
192
if (pthread_mutex_unlock (&lock->lock) != 0)
197
glthread_rwlock_unlock (gl_rwlock_t *lock)
199
if (pthread_mutex_lock (&lock->lock) != 0)
201
if (lock->runcount < 0)
203
/* Drop a writer lock. */
204
if (!(lock->runcount == -1))
210
/* Drop a reader lock. */
211
if (!(lock->runcount > 0))
215
if (lock->runcount == 0)
217
/* POSIX recommends that "write locks shall take precedence over read
218
locks", to avoid "writer starvation". */
219
if (lock->waiting_writers_count > 0)
221
/* Wake up one of the waiting writers. */
222
if (pthread_cond_signal (&lock->waiting_writers) != 0)
227
/* Wake up all waiting readers. */
228
if (pthread_cond_broadcast (&lock->waiting_readers) != 0)
232
if (pthread_mutex_unlock (&lock->lock) != 0)
237
glthread_rwlock_destroy (gl_rwlock_t *lock)
239
if (pthread_mutex_destroy (&lock->lock) != 0)
241
if (pthread_cond_destroy (&lock->waiting_readers) != 0)
243
if (pthread_cond_destroy (&lock->waiting_writers) != 0)
249
/* --------------------- gl_recursive_lock_t datatype --------------------- */
251
# if HAVE_PTHREAD_MUTEX_RECURSIVE
253
# if !(defined PTHREAD_RECURSIVE_MUTEX_INITIALIZER || defined PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP)
256
glthread_recursive_lock_init (gl_recursive_lock_t *lock)
258
pthread_mutexattr_t attributes;
260
if (pthread_mutexattr_init (&attributes) != 0)
262
if (pthread_mutexattr_settype (&attributes, PTHREAD_MUTEX_RECURSIVE) != 0)
264
if (pthread_mutex_init (&lock->recmutex, &attributes) != 0)
266
if (pthread_mutexattr_destroy (&attributes) != 0)
268
lock->initialized = 1;
272
glthread_recursive_lock_lock (gl_recursive_lock_t *lock)
274
if (!lock->initialized)
276
if (pthread_mutex_lock (&lock->guard) != 0)
278
if (!lock->initialized)
279
glthread_recursive_lock_init (lock);
280
if (pthread_mutex_unlock (&lock->guard) != 0)
283
if (pthread_mutex_lock (&lock->recmutex) != 0)
288
glthread_recursive_lock_unlock (gl_recursive_lock_t *lock)
290
if (!lock->initialized)
292
if (pthread_mutex_unlock (&lock->recmutex) != 0)
297
glthread_recursive_lock_destroy (gl_recursive_lock_t *lock)
299
if (!lock->initialized)
301
if (pthread_mutex_destroy (&lock->recmutex) != 0)
303
lock->initialized = 0;
311
glthread_recursive_lock_init (gl_recursive_lock_t *lock)
313
if (pthread_mutex_init (&lock->mutex, NULL) != 0)
315
lock->owner = (pthread_t) 0;
320
glthread_recursive_lock_lock (gl_recursive_lock_t *lock)
322
pthread_t self = pthread_self ();
323
if (lock->owner != self)
325
if (pthread_mutex_lock (&lock->mutex) != 0)
329
if (++(lock->depth) == 0) /* wraparound? */
334
glthread_recursive_lock_unlock (gl_recursive_lock_t *lock)
336
if (lock->owner != pthread_self ())
338
if (lock->depth == 0)
340
if (--(lock->depth) == 0)
342
lock->owner = (pthread_t) 0;
343
if (pthread_mutex_unlock (&lock->mutex) != 0)
349
glthread_recursive_lock_destroy (gl_recursive_lock_t *lock)
351
if (lock->owner != (pthread_t) 0)
353
if (pthread_mutex_destroy (&lock->mutex) != 0)
359
/* -------------------------- gl_once_t datatype -------------------------- */
361
static const pthread_once_t fresh_once = PTHREAD_ONCE_INIT;
364
glthread_once_singlethreaded (pthread_once_t *once_control)
366
/* We don't know whether pthread_once_t is an integer type, a floating-point
367
type, a pointer type, or a structure type. */
368
char *firstbyte = (char *)once_control;
369
if (*firstbyte == *(const char *)&fresh_once)
371
/* First time use of once_control. Invert the first byte. */
372
*firstbyte = ~ *(const char *)&fresh_once;
381
/* ========================================================================= */
385
/* Use the GNU Pth threads library. */
387
/* -------------------------- gl_lock_t datatype -------------------------- */
389
/* ------------------------- gl_rwlock_t datatype ------------------------- */
391
/* --------------------- gl_recursive_lock_t datatype --------------------- */
393
/* -------------------------- gl_once_t datatype -------------------------- */
396
glthread_once_call (void *arg)
398
void (**gl_once_temp_addr) (void) = (void (**) (void)) arg;
399
void (*initfunction) (void) = *gl_once_temp_addr;
404
glthread_once_singlethreaded (pth_once_t *once_control)
406
/* We know that pth_once_t is an integer type. */
407
if (*once_control == PTH_ONCE_INIT)
409
/* First time use of once_control. Invert the marker. */
410
*once_control = ~ PTH_ONCE_INIT;
419
/* ========================================================================= */
421
#if USE_SOLARIS_THREADS
423
/* Use the old Solaris threads library. */
425
/* -------------------------- gl_lock_t datatype -------------------------- */
427
/* ------------------------- gl_rwlock_t datatype ------------------------- */
429
/* --------------------- gl_recursive_lock_t datatype --------------------- */
432
glthread_recursive_lock_init (gl_recursive_lock_t *lock)
434
if (mutex_init (&lock->mutex, USYNC_THREAD, NULL) != 0)
436
lock->owner = (thread_t) 0;
441
glthread_recursive_lock_lock (gl_recursive_lock_t *lock)
443
thread_t self = thr_self ();
444
if (lock->owner != self)
446
if (mutex_lock (&lock->mutex) != 0)
450
if (++(lock->depth) == 0) /* wraparound? */
455
glthread_recursive_lock_unlock (gl_recursive_lock_t *lock)
457
if (lock->owner != thr_self ())
459
if (lock->depth == 0)
461
if (--(lock->depth) == 0)
463
lock->owner = (thread_t) 0;
464
if (mutex_unlock (&lock->mutex) != 0)
470
glthread_recursive_lock_destroy (gl_recursive_lock_t *lock)
472
if (lock->owner != (thread_t) 0)
474
if (mutex_destroy (&lock->mutex) != 0)
478
/* -------------------------- gl_once_t datatype -------------------------- */
481
glthread_once (gl_once_t *once_control, void (*initfunction) (void))
483
if (!once_control->inited)
485
/* Use the mutex to guarantee that if another thread is already calling
486
the initfunction, this thread waits until it's finished. */
487
if (mutex_lock (&once_control->mutex) != 0)
489
if (!once_control->inited)
491
once_control->inited = 1;
494
if (mutex_unlock (&once_control->mutex) != 0)
500
glthread_once_singlethreaded (gl_once_t *once_control)
502
/* We know that gl_once_t contains an integer type. */
503
if (!once_control->inited)
505
/* First time use of once_control. Invert the marker. */
506
once_control->inited = ~ 0;
515
/* ========================================================================= */
517
#if USE_WIN32_THREADS
519
/* -------------------------- gl_lock_t datatype -------------------------- */
522
glthread_lock_init (gl_lock_t *lock)
524
InitializeCriticalSection (&lock->lock);
525
lock->guard.done = 1;
529
glthread_lock_lock (gl_lock_t *lock)
531
if (!lock->guard.done)
533
if (InterlockedIncrement (&lock->guard.started) == 0)
534
/* This thread is the first one to need this lock. Initialize it. */
535
glthread_lock_init (lock);
537
/* Yield the CPU while waiting for another thread to finish
538
initializing this lock. */
539
while (!lock->guard.done)
542
EnterCriticalSection (&lock->lock);
546
glthread_lock_unlock (gl_lock_t *lock)
548
if (!lock->guard.done)
550
LeaveCriticalSection (&lock->lock);
554
glthread_lock_destroy (gl_lock_t *lock)
556
if (!lock->guard.done)
558
DeleteCriticalSection (&lock->lock);
559
lock->guard.done = 0;
562
/* ------------------------- gl_rwlock_t datatype ------------------------- */
565
gl_waitqueue_init (gl_waitqueue_t *wq)
573
/* Enqueues the current thread, represented by an event, in a wait queue.
574
Returns INVALID_HANDLE_VALUE if an allocation failure occurs. */
576
gl_waitqueue_add (gl_waitqueue_t *wq)
581
if (wq->count == wq->alloc)
583
unsigned int new_alloc = 2 * wq->alloc + 1;
585
(HANDLE *) realloc (wq->array, new_alloc * sizeof (HANDLE));
586
if (new_array == NULL)
587
/* No more memory. */
588
return INVALID_HANDLE_VALUE;
589
/* Now is a good opportunity to rotate the array so that its contents
590
starts at offset 0. */
593
unsigned int old_count = wq->count;
594
unsigned int old_alloc = wq->alloc;
595
unsigned int old_offset = wq->offset;
597
if (old_offset + old_count > old_alloc)
599
unsigned int limit = old_offset + old_count - old_alloc;
600
for (i = 0; i < limit; i++)
601
new_array[old_alloc + i] = new_array[i];
603
for (i = 0; i < old_count; i++)
604
new_array[i] = new_array[old_offset + i];
607
wq->array = new_array;
608
wq->alloc = new_alloc;
610
event = CreateEvent (NULL, TRUE, FALSE, NULL);
611
if (event == INVALID_HANDLE_VALUE)
612
/* No way to allocate an event. */
613
return INVALID_HANDLE_VALUE;
614
index = wq->offset + wq->count;
615
if (index >= wq->alloc)
617
wq->array[index] = event;
622
/* Notifies the first thread from a wait queue and dequeues it. */
624
gl_waitqueue_notify_first (gl_waitqueue_t *wq)
626
SetEvent (wq->array[wq->offset + 0]);
629
if (wq->count == 0 || wq->offset == wq->alloc)
633
/* Notifies all threads from a wait queue and dequeues them all. */
635
gl_waitqueue_notify_all (gl_waitqueue_t *wq)
639
for (i = 0; i < wq->count; i++)
641
unsigned int index = wq->offset + i;
642
if (index >= wq->alloc)
644
SetEvent (wq->array[index]);
651
glthread_rwlock_init (gl_rwlock_t *lock)
653
InitializeCriticalSection (&lock->lock);
654
gl_waitqueue_init (&lock->waiting_readers);
655
gl_waitqueue_init (&lock->waiting_writers);
657
lock->guard.done = 1;
661
glthread_rwlock_rdlock (gl_rwlock_t *lock)
663
if (!lock->guard.done)
665
if (InterlockedIncrement (&lock->guard.started) == 0)
666
/* This thread is the first one to need this lock. Initialize it. */
667
glthread_rwlock_init (lock);
669
/* Yield the CPU while waiting for another thread to finish
670
initializing this lock. */
671
while (!lock->guard.done)
674
EnterCriticalSection (&lock->lock);
675
/* Test whether only readers are currently running, and whether the runcount
676
field will not overflow. */
677
if (!(lock->runcount + 1 > 0))
679
/* This thread has to wait for a while. Enqueue it among the
681
HANDLE event = gl_waitqueue_add (&lock->waiting_readers);
682
if (event != INVALID_HANDLE_VALUE)
685
LeaveCriticalSection (&lock->lock);
686
/* Wait until another thread signals this event. */
687
result = WaitForSingleObject (event, INFINITE);
688
if (result == WAIT_FAILED || result == WAIT_TIMEOUT)
691
/* The thread which signalled the event already did the bookkeeping:
692
removed us from the waiting_readers, incremented lock->runcount. */
693
if (!(lock->runcount > 0))
699
/* Allocation failure. Weird. */
702
LeaveCriticalSection (&lock->lock);
704
EnterCriticalSection (&lock->lock);
706
while (!(lock->runcount + 1 > 0));
710
LeaveCriticalSection (&lock->lock);
714
glthread_rwlock_wrlock (gl_rwlock_t *lock)
716
if (!lock->guard.done)
718
if (InterlockedIncrement (&lock->guard.started) == 0)
719
/* This thread is the first one to need this lock. Initialize it. */
720
glthread_rwlock_init (lock);
722
/* Yield the CPU while waiting for another thread to finish
723
initializing this lock. */
724
while (!lock->guard.done)
727
EnterCriticalSection (&lock->lock);
728
/* Test whether no readers or writers are currently running. */
729
if (!(lock->runcount == 0))
731
/* This thread has to wait for a while. Enqueue it among the
733
HANDLE event = gl_waitqueue_add (&lock->waiting_writers);
734
if (event != INVALID_HANDLE_VALUE)
737
LeaveCriticalSection (&lock->lock);
738
/* Wait until another thread signals this event. */
739
result = WaitForSingleObject (event, INFINITE);
740
if (result == WAIT_FAILED || result == WAIT_TIMEOUT)
743
/* The thread which signalled the event already did the bookkeeping:
744
removed us from the waiting_writers, set lock->runcount = -1. */
745
if (!(lock->runcount == -1))
751
/* Allocation failure. Weird. */
754
LeaveCriticalSection (&lock->lock);
756
EnterCriticalSection (&lock->lock);
758
while (!(lock->runcount == 0));
761
lock->runcount--; /* runcount becomes -1 */
762
LeaveCriticalSection (&lock->lock);
766
glthread_rwlock_unlock (gl_rwlock_t *lock)
768
if (!lock->guard.done)
770
EnterCriticalSection (&lock->lock);
771
if (lock->runcount < 0)
773
/* Drop a writer lock. */
774
if (!(lock->runcount == -1))
780
/* Drop a reader lock. */
781
if (!(lock->runcount > 0))
785
if (lock->runcount == 0)
787
/* POSIX recommends that "write locks shall take precedence over read
788
locks", to avoid "writer starvation". */
789
if (lock->waiting_writers.count > 0)
791
/* Wake up one of the waiting writers. */
793
gl_waitqueue_notify_first (&lock->waiting_writers);
797
/* Wake up all waiting readers. */
798
lock->runcount += lock->waiting_readers.count;
799
gl_waitqueue_notify_all (&lock->waiting_readers);
802
LeaveCriticalSection (&lock->lock);
806
glthread_rwlock_destroy (gl_rwlock_t *lock)
808
if (!lock->guard.done)
810
if (lock->runcount != 0)
812
DeleteCriticalSection (&lock->lock);
813
if (lock->waiting_readers.array != NULL)
814
free (lock->waiting_readers.array);
815
if (lock->waiting_writers.array != NULL)
816
free (lock->waiting_writers.array);
817
lock->guard.done = 0;
820
/* --------------------- gl_recursive_lock_t datatype --------------------- */
823
glthread_recursive_lock_init (gl_recursive_lock_t *lock)
827
InitializeCriticalSection (&lock->lock);
828
lock->guard.done = 1;
832
glthread_recursive_lock_lock (gl_recursive_lock_t *lock)
834
if (!lock->guard.done)
836
if (InterlockedIncrement (&lock->guard.started) == 0)
837
/* This thread is the first one to need this lock. Initialize it. */
838
glthread_recursive_lock_init (lock);
840
/* Yield the CPU while waiting for another thread to finish
841
initializing this lock. */
842
while (!lock->guard.done)
846
DWORD self = GetCurrentThreadId ();
847
if (lock->owner != self)
849
EnterCriticalSection (&lock->lock);
852
if (++(lock->depth) == 0) /* wraparound? */
858
glthread_recursive_lock_unlock (gl_recursive_lock_t *lock)
860
if (lock->owner != GetCurrentThreadId ())
862
if (lock->depth == 0)
864
if (--(lock->depth) == 0)
867
LeaveCriticalSection (&lock->lock);
872
glthread_recursive_lock_destroy (gl_recursive_lock_t *lock)
874
if (lock->owner != 0)
876
DeleteCriticalSection (&lock->lock);
877
lock->guard.done = 0;
880
/* -------------------------- gl_once_t datatype -------------------------- */
883
glthread_once (gl_once_t *once_control, void (*initfunction) (void))
885
if (once_control->inited <= 0)
887
if (InterlockedIncrement (&once_control->started) == 0)
889
/* This thread is the first one to come to this once_control. */
890
InitializeCriticalSection (&once_control->lock);
891
EnterCriticalSection (&once_control->lock);
892
once_control->inited = 0;
894
once_control->inited = 1;
895
LeaveCriticalSection (&once_control->lock);
899
/* Undo last operation. */
900
InterlockedDecrement (&once_control->started);
901
/* Some other thread has already started the initialization.
902
Yield the CPU while waiting for the other thread to finish
903
initializing and taking the lock. */
904
while (once_control->inited < 0)
906
if (once_control->inited <= 0)
908
/* Take the lock. This blocks until the other thread has
909
finished calling the initfunction. */
910
EnterCriticalSection (&once_control->lock);
911
LeaveCriticalSection (&once_control->lock);
912
if (!(once_control->inited > 0))
921
/* ========================================================================= */