diff options
Diffstat (limited to 'win32/contrib/pthreads/rwlock.c')
| -rw-r--r-- | win32/contrib/pthreads/rwlock.c | 616 |
1 files changed, 616 insertions, 0 deletions
diff --git a/win32/contrib/pthreads/rwlock.c b/win32/contrib/pthreads/rwlock.c new file mode 100644 index 000000000..2bb62f1e5 --- /dev/null +++ b/win32/contrib/pthreads/rwlock.c @@ -0,0 +1,616 @@ +/*
+ * rwlock.c
+ *
+ * Description:
+ * This translation unit implements read/write lock primitives.
+ *
+ * Pthreads-win32 - POSIX Threads Library for Win32
+ * Copyright (C) 1998
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with this library; if not, write to the Free
+ * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
+ * MA 02111-1307, USA
+ */
+
+#include <errno.h>
+#include <limits.h>
+
+#include "pthread.h"
+#include "implement.h"
+
+static INLINE int
+ptw32_rwlock_check_need_init(pthread_rwlock_t *rwlock)
+{
+ int result = 0;
+
+ /*
+ * The following guarded test is specifically for statically
+ * initialised rwlocks (via PTHREAD_RWLOCK_INITIALIZER).
+ *
+ * Note that by not providing this synchronisation we risk
+ * introducing race conditions into applications which are
+ * correctly written.
+ *
+ * Approach
+ * --------
+ * We know that static rwlocks will not be PROCESS_SHARED
+ * so we can serialise access to internal state using
+ * Win32 Critical Sections rather than Win32 Mutexes.
+ *
+ * If using a single global lock slows applications down too much,
+ * multiple global locks could be created and hashed on some random
+ * value associated with each mutex, the pointer perhaps. At a guess,
+ * a good value for the optimal number of global locks might be
+ * the number of processors + 1.
+ *
+ */
+ EnterCriticalSection(&ptw32_rwlock_test_init_lock);
+
+ /*
+ * We got here possibly under race
+ * conditions. Check again inside the critical section
+ * and only initialise if the rwlock is valid (not been destroyed).
+ * If a static rwlock has been destroyed, the application can
+ * re-initialise it only by calling pthread_rwlock_init()
+ * explicitly.
+ */
+ if (*rwlock == PTHREAD_RWLOCK_INITIALIZER)
+ {
+ result = pthread_rwlock_init(rwlock, NULL);
+ }
+ else if (*rwlock == NULL)
+ {
+ /*
+ * The rwlock has been destroyed while we were waiting to
+ * initialise it, so the operation that caused the
+ * auto-initialisation should fail.
+ */
+ result = EINVAL;
+ }
+
+ LeaveCriticalSection(&ptw32_rwlock_test_init_lock);
+
+ return result;
+}
+
+int
+pthread_rwlock_init(pthread_rwlock_t *rwlock, const pthread_rwlockattr_t *attr)
+{
+ int result;
+ pthread_rwlock_t rwl = 0;
+
+ if (rwlock == NULL)
+ {
+ return EINVAL;
+ }
+
+ if (attr != NULL && *attr != NULL)
+ {
+ result = EINVAL; /* Not supported */
+ goto DONE;
+ }
+
+ rwl = (pthread_rwlock_t) calloc(1, sizeof(*rwl));
+
+ if (rwl == NULL)
+ {
+ result = ENOMEM;
+ goto DONE;
+ }
+
+ rwl->nSharedAccessCount = 0;
+ rwl->nExclusiveAccessCount = 0;
+ rwl->nCompletedSharedAccessCount = 0;
+
+ result = pthread_mutex_init(&rwl->mtxExclusiveAccess, NULL);
+ if (result != 0)
+ {
+ goto FAIL0;
+ }
+
+ result = pthread_mutex_init(&rwl->mtxSharedAccessCompleted, NULL);
+ if (result != 0)
+ {
+ goto FAIL1;
+ }
+
+ result = pthread_cond_init(&rwl->cndSharedAccessCompleted, NULL);
+ if (result != 0)
+ {
+ goto FAIL2;
+ }
+
+ rwl->nMagic = PTW32_RWLOCK_MAGIC;
+
+ result = 0;
+ goto DONE;
+
+FAIL2:
+ (void) pthread_mutex_destroy(&(rwl->mtxSharedAccessCompleted));
+
+FAIL1:
+ (void) pthread_mutex_destroy(&(rwl->mtxExclusiveAccess));
+
+FAIL0:
+ (void) free(rwl);
+ rwl = NULL;
+
+DONE:
+ *rwlock = rwl;
+
+ return result;
+}
+
+int
+pthread_rwlock_destroy(pthread_rwlock_t *rwlock)
+{
+ pthread_rwlock_t rwl;
+ int result = 0, result1 = 0, result2 = 0;
+
+ if (rwlock == NULL || *rwlock == NULL)
+ {
+ return EINVAL;
+ }
+
+ if (*rwlock != PTHREAD_RWLOCK_INITIALIZER)
+ {
+ rwl = *rwlock;
+
+ if (rwl->nMagic != PTW32_RWLOCK_MAGIC)
+ {
+ return EINVAL;
+ }
+
+ if ((result = pthread_mutex_lock(&(rwl->mtxExclusiveAccess))) != 0)
+ {
+ return result;
+ }
+
+ if ((result = pthread_mutex_lock(&(rwl->mtxSharedAccessCompleted))) != 0)
+ {
+ (void) pthread_mutex_unlock(&(rwl->mtxExclusiveAccess));
+ return result;
+ }
+
+ /*
+ * Check whether any threads own/wait for the lock (wait for ex.access);
+ * report "BUSY" if so.
+ */
+ if (rwl->nExclusiveAccessCount > 0
+ || rwl->nSharedAccessCount > rwl->nCompletedSharedAccessCount)
+ {
+ result = pthread_mutex_unlock(&(rwl->mtxSharedAccessCompleted));
+ result1 = pthread_mutex_unlock(&(rwl->mtxExclusiveAccess));
+ result2 = EBUSY;
+ }
+ else
+ {
+ rwl->nMagic = 0;
+
+ if ((result = pthread_mutex_unlock(&(rwl->mtxSharedAccessCompleted))) != 0)
+ {
+ pthread_mutex_unlock(&rwl->mtxExclusiveAccess);
+ return result;
+ }
+
+ if ((result = pthread_mutex_unlock(&(rwl->mtxExclusiveAccess))) != 0)
+ {
+ return result;
+ }
+
+ *rwlock = NULL; /* Invalidate rwlock before anything else */
+ result = pthread_cond_destroy(&(rwl->cndSharedAccessCompleted));
+ result1 = pthread_mutex_destroy(&(rwl->mtxSharedAccessCompleted));
+ result2 = pthread_mutex_destroy(&(rwl->mtxExclusiveAccess));
+ (void) free(rwl);
+ }
+ }
+ else
+ {
+ /*
+ * See notes in ptw32_rwlock_check_need_init() above also.
+ */
+ EnterCriticalSection(&ptw32_rwlock_test_init_lock);
+
+ /*
+ * Check again.
+ */
+ if (*rwlock == PTHREAD_RWLOCK_INITIALIZER)
+ {
+ /*
+ * This is all we need to do to destroy a statically
+ * initialised rwlock that has not yet been used (initialised).
+ * If we get to here, another thread
+ * waiting to initialise this rwlock will get an EINVAL.
+ */
+ *rwlock = NULL;
+ }
+ else
+ {
+ /*
+ * The rwlock has been initialised while we were waiting
+ * so assume it's in use.
+ */
+ result = EBUSY;
+ }
+
+ LeaveCriticalSection(&ptw32_rwlock_test_init_lock);
+ }
+
+ return ((result != 0) ? result : ((result1 != 0) ? result1 : result2));
+}
+
+int
+pthread_rwlock_rdlock(pthread_rwlock_t *rwlock)
+{
+ int result;
+ pthread_rwlock_t rwl;
+
+ if (rwlock == NULL || *rwlock == NULL)
+ {
+ return EINVAL;
+ }
+
+ /*
+ * We do a quick check to see if we need to do more work
+ * to initialise a static rwlock. We check
+ * again inside the guarded section of ptw32_rwlock_check_need_init()
+ * to avoid race conditions.
+ */
+ if (*rwlock == PTHREAD_RWLOCK_INITIALIZER)
+ {
+ result = ptw32_rwlock_check_need_init(rwlock);
+
+ if (result != 0 && result != EBUSY)
+ {
+ return result;
+ }
+ }
+
+ rwl = *rwlock;
+
+ if (rwl->nMagic != PTW32_RWLOCK_MAGIC)
+ {
+ return EINVAL;
+ }
+
+ if ((result = pthread_mutex_lock(&(rwl->mtxExclusiveAccess))) != 0)
+ {
+ return result;
+ }
+
+ if (++rwl->nSharedAccessCount == INT_MAX)
+ {
+ if ((result = pthread_mutex_lock(&(rwl->mtxSharedAccessCompleted))) != 0)
+ {
+ (void) pthread_mutex_unlock(&(rwl->mtxExclusiveAccess));
+ return result;
+ }
+
+ rwl->nSharedAccessCount -= rwl->nCompletedSharedAccessCount;
+ rwl->nCompletedSharedAccessCount = 0;
+
+ if ((result = pthread_mutex_unlock(&(rwl->mtxSharedAccessCompleted))) != 0)
+ {
+ (void) pthread_mutex_unlock(&(rwl->mtxExclusiveAccess));
+ return result;
+ }
+ }
+
+ return (pthread_mutex_unlock(&(rwl->mtxExclusiveAccess)));
+}
+
+static void
+ptw32_rwlock_cancelwrwait(void * arg)
+{
+ pthread_rwlock_t rwl = (pthread_rwlock_t) arg;
+
+ rwl->nSharedAccessCount = -rwl->nCompletedSharedAccessCount;
+ rwl->nCompletedSharedAccessCount = 0;
+
+ (void) pthread_mutex_unlock(&(rwl->mtxSharedAccessCompleted));
+ (void) pthread_mutex_unlock(&(rwl->mtxExclusiveAccess));
+}
+
+int
+pthread_rwlock_wrlock(pthread_rwlock_t * rwlock)
+{
+ int result;
+ pthread_rwlock_t rwl;
+
+ if (rwlock == NULL || *rwlock == NULL)
+ {
+ return EINVAL;
+ }
+
+ /*
+ * We do a quick check to see if we need to do more work
+ * to initialise a static rwlock. We check
+ * again inside the guarded section of ptw32_rwlock_check_need_init()
+ * to avoid race conditions.
+ */
+ if (*rwlock == PTHREAD_RWLOCK_INITIALIZER)
+ {
+ result = ptw32_rwlock_check_need_init(rwlock);
+
+ if (result != 0 && result != EBUSY)
+ {
+ return result;
+ }
+ }
+
+ rwl = *rwlock;
+
+ if (rwl->nMagic != PTW32_RWLOCK_MAGIC)
+ {
+ return EINVAL;
+ }
+
+ if ((result = pthread_mutex_lock(&(rwl->mtxExclusiveAccess))) != 0)
+ {
+ return result;
+ }
+
+ if ((result = pthread_mutex_lock(&(rwl->mtxSharedAccessCompleted))) != 0)
+ {
+ (void) pthread_mutex_unlock(&(rwl->mtxExclusiveAccess));
+ return result;
+ }
+
+ if (rwl->nExclusiveAccessCount == 0)
+ {
+ if (rwl->nCompletedSharedAccessCount > 0)
+ {
+ rwl->nSharedAccessCount -= rwl->nCompletedSharedAccessCount;
+ rwl->nCompletedSharedAccessCount = 0;
+ }
+
+ if (rwl->nSharedAccessCount > 0)
+ {
+ /*
+ * pthread_rwlock_wrlock() is not a cancelation point
+ * so temporarily prevent pthread_cond_wait() from being one.
+ */
+ pthread_t self = pthread_self();
+ int oldCancelState;
+
+ rwl->nCompletedSharedAccessCount = -rwl->nSharedAccessCount;
+
+ if (self->cancelType == PTHREAD_CANCEL_DEFERRED)
+ {
+ pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &oldCancelState);
+ }
+
+ /* Could still be PTHREAD_CANCEL_ASYNCHRONOUS. */
+ pthread_cleanup_push(ptw32_rwlock_cancelwrwait, (void*)rwl);
+
+ do
+ {
+ result = pthread_cond_wait(&(rwl->cndSharedAccessCompleted),
+ &(rwl->mtxSharedAccessCompleted));
+ }
+ while (result == 0 && rwl->nCompletedSharedAccessCount < 0);
+
+ if (self->cancelType == PTHREAD_CANCEL_DEFERRED)
+ {
+ pthread_setcancelstate(oldCancelState, NULL);
+ }
+
+ pthread_cleanup_pop ((result != 0) ? 1 : 0);
+
+ if (result == 0)
+ {
+ rwl->nSharedAccessCount = 0;
+ }
+ }
+ }
+
+ if (result == 0)
+ {
+ rwl->nExclusiveAccessCount++;
+ }
+
+ return result;
+}
+
+int
+pthread_rwlock_unlock(pthread_rwlock_t * rwlock)
+{
+ int result, result1;
+ pthread_rwlock_t rwl;
+
+ if (rwlock == NULL || *rwlock == NULL)
+ {
+ return(EINVAL);
+ }
+
+ if (*rwlock == PTHREAD_RWLOCK_INITIALIZER)
+ {
+ /*
+ * Assume any race condition here is harmless.
+ */
+ return 0;
+ }
+
+ rwl = *rwlock;
+
+ if (rwl->nMagic != PTW32_RWLOCK_MAGIC)
+ {
+ return EINVAL;
+ }
+
+ if (rwl->nExclusiveAccessCount == 0)
+ {
+ if ((result = pthread_mutex_lock(&(rwl->mtxSharedAccessCompleted))) != 0)
+ {
+ return result;
+ }
+
+ if (++rwl->nCompletedSharedAccessCount == 0)
+ {
+ result = pthread_cond_signal(&(rwl->cndSharedAccessCompleted));
+ }
+
+ result1 = pthread_mutex_unlock(&(rwl->mtxSharedAccessCompleted));
+ }
+ else
+ {
+ rwl->nExclusiveAccessCount--;
+
+ result = pthread_mutex_unlock(&(rwl->mtxSharedAccessCompleted));
+ result1 = pthread_mutex_unlock(&(rwl->mtxExclusiveAccess));
+
+ }
+
+ return ((result != 0) ? result : result1);
+}
+
+int
+pthread_rwlock_tryrdlock(pthread_rwlock_t * rwlock)
+{
+ int result;
+ pthread_rwlock_t rwl;
+
+ if (rwlock == NULL || *rwlock == NULL)
+ {
+ return EINVAL;
+ }
+
+ /*
+ * We do a quick check to see if we need to do more work
+ * to initialise a static rwlock. We check
+ * again inside the guarded section of ptw32_rwlock_check_need_init()
+ * to avoid race conditions.
+ */
+ if (*rwlock == PTHREAD_RWLOCK_INITIALIZER)
+ {
+ result = ptw32_rwlock_check_need_init(rwlock);
+
+ if (result != 0 && result != EBUSY)
+ {
+ return result;
+ }
+ }
+
+ rwl = *rwlock;
+
+ if (rwl->nMagic != PTW32_RWLOCK_MAGIC)
+ {
+ return EINVAL;
+ }
+
+ if ((result = pthread_mutex_trylock(&(rwl->mtxExclusiveAccess))) != 0)
+ {
+ return result;
+ }
+
+ if (++rwl->nSharedAccessCount == INT_MAX)
+ {
+ if ((result = pthread_mutex_lock(&(rwl->mtxSharedAccessCompleted))) != 0)
+ {
+ (void) pthread_mutex_unlock(&(rwl->mtxExclusiveAccess));
+ return result;
+ }
+
+ rwl->nSharedAccessCount -= rwl->nCompletedSharedAccessCount;
+ rwl->nCompletedSharedAccessCount = 0;
+
+ if ((result = pthread_mutex_unlock(&(rwl->mtxSharedAccessCompleted))) != 0)
+ {
+ (void) pthread_mutex_unlock(&(rwl->mtxExclusiveAccess));
+ return result;
+ }
+ }
+
+ return (pthread_mutex_unlock(&rwl->mtxExclusiveAccess));
+}
+
+int
+pthread_rwlock_trywrlock(pthread_rwlock_t * rwlock)
+{
+ int result, result1;
+ pthread_rwlock_t rwl;
+
+ if (rwlock == NULL || *rwlock == NULL)
+ {
+ return EINVAL;
+ }
+
+ /*
+ * We do a quick check to see if we need to do more work
+ * to initialise a static rwlock. We check
+ * again inside the guarded section of ptw32_rwlock_check_need_init()
+ * to avoid race conditions.
+ */
+ if (*rwlock == PTHREAD_RWLOCK_INITIALIZER)
+ {
+ result = ptw32_rwlock_check_need_init(rwlock);
+
+ if (result != 0 && result != EBUSY)
+ {
+ return result;
+ }
+ }
+
+ rwl = *rwlock;
+
+ if (rwl->nMagic != PTW32_RWLOCK_MAGIC)
+ {
+ return EINVAL;
+ }
+
+ if ((result = pthread_mutex_trylock(&(rwl->mtxExclusiveAccess))) != 0)
+ {
+ return result;
+ }
+
+ if ((result = pthread_mutex_trylock(&(rwl->mtxSharedAccessCompleted))) != 0)
+ {
+ result1 = pthread_mutex_unlock(&(rwl->mtxExclusiveAccess));
+ return ((result1 != 0) ? result1 : result);
+ }
+
+ if (rwl->nExclusiveAccessCount == 0)
+ {
+ if (rwl->nCompletedSharedAccessCount > 0)
+ {
+ rwl->nSharedAccessCount -= rwl->nCompletedSharedAccessCount;
+ rwl->nCompletedSharedAccessCount = 0;
+ }
+
+ if (rwl->nSharedAccessCount > 0)
+ {
+ if ((result = pthread_mutex_unlock(&(rwl->mtxSharedAccessCompleted))) != 0)
+ {
+ (void) pthread_mutex_unlock(&(rwl->mtxExclusiveAccess));
+ return result;
+ }
+
+ if ((result = pthread_mutex_unlock(&(rwl->mtxExclusiveAccess))) == 0)
+ {
+ result = EBUSY;
+ }
+ }
+ else
+ {
+ rwl->nExclusiveAccessCount = 1;
+ }
+ }
+ else
+ {
+ result = EBUSY;
+ }
+
+ return result;
+}
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