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Diffstat (limited to 'condvar_destroy.c')
| -rw-r--r-- | condvar_destroy.c | 222 |
1 files changed, 222 insertions, 0 deletions
diff --git a/condvar_destroy.c b/condvar_destroy.c new file mode 100644 index 0000000..d0af374 --- /dev/null +++ b/condvar_destroy.c @@ -0,0 +1,222 @@ +/* + * condvar_destroy.c + * + * Description: + * This translation unit implements condition variables and their primitives. + * + * + * -------------------------------------------------------------------------- + * + * Pthreads-win32 - POSIX Threads Library for Win32 + * Copyright(C) 1998 John E. Bossom + * Copyright(C) 1999,2002 Pthreads-win32 contributors + * + * Contact Email: rpj@ise.canberra.edu.au + * + * The current list of contributors is contained + * in the file CONTRIBUTORS included with the source + * code distribution. The list can also be seen at the + * following World Wide Web location: + * http://sources.redhat.com/pthreads-win32/contributors.html + * + * This library is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser 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 + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with this library in the file COPYING.LIB; + * if not, write to the Free Software Foundation, Inc., + * 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA + */ + +#include "pthread.h" +#include "implement.h" + + +int +pthread_cond_destroy (pthread_cond_t * cond) + /* + * ------------------------------------------------------ + * DOCPUBLIC + * This function destroys a condition variable + * + * + * PARAMETERS + * cond + * pointer to an instance of pthread_cond_t + * + * + * DESCRIPTION + * This function destroys a condition variable. + * + * NOTES: + * 1) A condition variable can be destroyed + * immediately after all the threads that + * are blocked on it are awakened. e.g. + * + * struct list { + * pthread_mutex_t lm; + * ... + * } + * + * struct elt { + * key k; + * int busy; + * pthread_cond_t notbusy; + * ... + * } + * + * + * struct elt * + * list_find(struct list *lp, key k) + * { + * struct elt *ep; + * + * pthread_mutex_lock(&lp->lm); + * while ((ep = find_elt(l,k) != NULL) && ep->busy) + * pthread_cond_wait(&ep->notbusy, &lp->lm); + * if (ep != NULL) + * ep->busy = 1; + * pthread_mutex_unlock(&lp->lm); + * return(ep); + * } + * + * delete_elt(struct list *lp, struct elt *ep) + * { + * pthread_mutex_lock(&lp->lm); + * assert(ep->busy); + * ... remove ep from list ... + * ep->busy = 0; + * (A) pthread_cond_broadcast(&ep->notbusy); + * pthread_mutex_unlock(&lp->lm); + * (B) pthread_cond_destroy(&rp->notbusy); + * free(ep); + * } + * + * In this example, the condition variable + * and its list element may be freed (line B) + * immediately after all threads waiting for + * it are awakened (line A), since the mutex + * and the code ensure that no other thread + * can touch the element to be deleted. + * + * RESULTS + * 0 successfully released condition variable, + * EINVAL 'cond' is invalid, + * EBUSY 'cond' is in use, + * + * ------------------------------------------------------ + */ +{ + pthread_cond_t cv; + int result = 0, result1 = 0, result2 = 0; + + /* + * Assuming any race condition here is harmless. + */ + if (cond == NULL + || *cond == NULL) + { + return EINVAL; + } + + if (*cond != PTHREAD_COND_INITIALIZER) + { + cv = *cond; + + /* + * Close the gate; this will synchronize this thread with + * all already signaled waiters to let them retract their + * waiter status - SEE NOTE 1 ABOVE!!! + */ + if (sem_wait(&(cv->semBlockLock)) != 0) + { + return errno; + } + + /* + * !TRY! lock mtxUnblockLock; try will detect busy condition + * and will not course a deadlock with respect to concurrent + * signal/broadcast. + */ + if ((result = pthread_mutex_trylock(&(cv->mtxUnblockLock))) != 0) + { + (void) sem_post(&(cv->semBlockLock)); + return result; + } + + /* + * Check whether cv is still busy (still has waiters) + */ + if (cv->nWaitersBlocked > cv->nWaitersGone) + { + if (sem_post(&(cv->semBlockLock)) != 0) + { + result = errno; + } + result1 = pthread_mutex_unlock(&(cv->mtxUnblockLock)); + result2 = EBUSY; + } + else + { + /* + * Now it is safe to destroy + */ + *cond = NULL; + if (sem_destroy(&(cv->semBlockLock)) != 0) + { + result = errno; + } + if (sem_destroy(&(cv->semBlockQueue)) != 0) + { + result1 = errno; + } + if ((result2 = pthread_mutex_unlock(&(cv->mtxUnblockLock))) == 0) + { + result2 = pthread_mutex_destroy(&(cv->mtxUnblockLock)); + } + + (void) free(cv); + } + } + else + { + /* + * See notes in ptw32_cond_check_need_init() above also. + */ + EnterCriticalSection(&ptw32_cond_test_init_lock); + + /* + * Check again. + */ + if (*cond == PTHREAD_COND_INITIALIZER) + { + /* + * This is all we need to do to destroy a statically + * initialised cond that has not yet been used (initialised). + * If we get to here, another thread waiting to initialise + * this cond will get an EINVAL. That's OK. + */ + *cond = NULL; + } + else + { + /* + * The cv has been initialised while we were waiting + * so assume it's in use. + */ + result = EBUSY; + } + + LeaveCriticalSection(&ptw32_cond_test_init_lock); + } + + return ((result != 0) ? result : ((result1 != 0) ? result1 : result2)); + +} |