diff options
Diffstat (limited to 'rwlock.c')
| -rw-r--r-- | rwlock.c | 826 |
1 files changed, 12 insertions, 814 deletions
@@ -34,817 +34,15 @@ * 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_rwlockattr_init (pthread_rwlockattr_t * attr) - /* - * ------------------------------------------------------ - * DOCPUBLIC - * Initializes a rwlock attributes object with default - * attributes. - * - * PARAMETERS - * attr - * pointer to an instance of pthread_rwlockattr_t - * - * - * DESCRIPTION - * Initializes a rwlock attributes object with default - * attributes. - * - * RESULTS - * 0 successfully initialized attr, - * ENOMEM insufficient memory for attr. - * - * ------------------------------------------------------ - */ -{ - int result = 0; - pthread_rwlockattr_t rwa; - - rwa = (pthread_rwlockattr_t) calloc (1, sizeof (*rwa)); - - if (rwa == NULL) - { - result = ENOMEM; - } - else - { - rwa->pshared = PTHREAD_PROCESS_PRIVATE; - } - - *attr = rwa; - - return(result); -} /* pthread_rwlockattr_init */ - - -int -pthread_rwlockattr_destroy (pthread_rwlockattr_t * attr) - /* - * ------------------------------------------------------ - * DOCPUBLIC - * Destroys a rwlock attributes object. The object can - * no longer be used. - * - * PARAMETERS - * attr - * pointer to an instance of pthread_rwlockattr_t - * - * - * DESCRIPTION - * Destroys a rwlock attributes object. The object can - * no longer be used. - * - * NOTES: - * 1) Does not affect rwlockss created using 'attr' - * - * RESULTS - * 0 successfully released attr, - * EINVAL 'attr' is invalid. - * - * ------------------------------------------------------ - */ -{ - int result = 0; - - if (attr == NULL || *attr == NULL) - { - result = EINVAL; - } - else - { - pthread_rwlockattr_t rwa = *attr; - - *attr = NULL; - free (rwa); - } - - return(result); -} /* pthread_rwlockattr_destroy */ - - -int -pthread_rwlockattr_getpshared (const pthread_rwlockattr_t * attr, - int *pshared) - /* - * ------------------------------------------------------ - * DOCPUBLIC - * Determine whether rwlocks created with 'attr' can be - * shared between processes. - * - * PARAMETERS - * attr - * pointer to an instance of pthread_rwlockattr_t - * - * pshared - * will be set to one of: - * - * PTHREAD_PROCESS_SHARED - * May be shared if in shared memory - * - * PTHREAD_PROCESS_PRIVATE - * Cannot be shared. - * - * - * DESCRIPTION - * Rwlocks creatd with 'attr' can be shared between - * processes if pthread_rwlock_t variable is allocated - * in memory shared by these processes. - * NOTES: - * 1) pshared rwlocks MUST be allocated in shared - * memory. - * 2) The following macro is defined if shared rwlocks - * are supported: - * _POSIX_THREAD_PROCESS_SHARED - * - * RESULTS - * 0 successfully retrieved attribute, - * EINVAL 'attr' is invalid, - * - * ------------------------------------------------------ - */ -{ - int result; - - if ((attr != NULL && *attr != NULL) && - (pshared != NULL)) - { - *pshared = (*attr)->pshared; - result = 0; - } - else - { - result = EINVAL; - } - - return (result); - -} /* pthread_rwlockattr_getpshared */ - - -int -pthread_rwlockattr_setpshared (pthread_rwlockattr_t * attr, - int pshared) - /* - * ------------------------------------------------------ - * DOCPUBLIC - * Rwlocks created with 'attr' can be shared between - * processes if pthread_rwlock_t variable is allocated - * in memory shared by these processes. - * - * PARAMETERS - * attr - * pointer to an instance of pthread_rwlockattr_t - * - * pshared - * must be one of: - * - * PTHREAD_PROCESS_SHARED - * May be shared if in shared memory - * - * PTHREAD_PROCESS_PRIVATE - * Cannot be shared. - * - * DESCRIPTION - * Rwlocks creatd with 'attr' can be shared between - * processes if pthread_rwlock_t variable is allocated - * in memory shared by these processes. - * - * NOTES: - * 1) pshared rwlocks MUST be allocated in shared - * memory. - * - * 2) The following macro is defined if shared rwlocks - * are supported: - * _POSIX_THREAD_PROCESS_SHARED - * - * RESULTS - * 0 successfully set attribute, - * EINVAL 'attr' or pshared is invalid, - * ENOSYS PTHREAD_PROCESS_SHARED not supported, - * - * ------------------------------------------------------ - */ -{ - int result; - - if ((attr != NULL && *attr != NULL) && - ((pshared == PTHREAD_PROCESS_SHARED) || - (pshared == PTHREAD_PROCESS_PRIVATE))) - { - if (pshared == PTHREAD_PROCESS_SHARED) - { - -#if !defined( _POSIX_THREAD_PROCESS_SHARED ) - - result = ENOSYS; - pshared = PTHREAD_PROCESS_PRIVATE; - -#else - - result = 0; - -#endif /* _POSIX_THREAD_PROCESS_SHARED */ - - } - else - { - result = 0; - } - - (*attr)->pshared = pshared; - } - else - { - result = EINVAL; - } - - return (result); - -} /* pthread_rwlockattr_setpshared */ - - -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) - { - rwl->nCompletedSharedAccessCount = -rwl->nSharedAccessCount; - - /* - * This routine may be a cancelation point - * according to POSIX 1003.1j section 18.1.2. - */ -#ifdef _MSC_VER -#pragma inline_depth(0) -#endif - pthread_cleanup_push(ptw32_rwlock_cancelwrwait, (void*)rwl); - - do - { - result = pthread_cond_wait(&(rwl->cndSharedAccessCompleted), - &(rwl->mtxSharedAccessCompleted)); - } - while (result == 0 && rwl->nCompletedSharedAccessCount < 0); - - pthread_cleanup_pop ((result != 0) ? 1 : 0); -#ifdef _MSC_VER -#pragma inline_depth() -#endif - - 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; -} +#include "ptw32_rwlock_check_need_init.c" +#include "pthread_rwlock_init.c" +#include "pthread_rwlock_destroy.c" +#include "pthread_rwlockattr_init.c" +#include "pthread_rwlockattr_destroy.c" +#include "pthread_rwlockattr_getpshared.c" +#include "pthread_rwlockattr_setpshared.c" +#include "pthread_rwlock_rdlock.c" +#include "pthread_rwlock_wrlock.c" +#include "pthread_rwlock_unlock.c" +#include "pthread_rwlock_tryrdlock.c" +#include "pthread_rwlock_trywrlock.c" |