254 lines
7.5 KiB
C
254 lines
7.5 KiB
C
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/*
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* pthread_cond_destroy.c
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*
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* Description:
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* This translation unit implements condition variables and their primitives.
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*
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*
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* --------------------------------------------------------------------------
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*
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* Pthreads-win32 - POSIX Threads Library for Win32
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* Copyright(C) 1998 John E. Bossom
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* Copyright(C) 1999,2005 Pthreads-win32 contributors
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*
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* Contact Email: rpj@callisto.canberra.edu.au
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*
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* The current list of contributors is contained
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* in the file CONTRIBUTORS included with the source
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* code distribution. The list can also be seen at the
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* following World Wide Web location:
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* http://sources.redhat.com/pthreads-win32/contributors.html
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library in the file COPYING.LIB;
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* if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
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*/
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#include "pthread.h"
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#include "implement.h"
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int
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pthread_cond_destroy (pthread_cond_t * cond)
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/*
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* ------------------------------------------------------
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* DOCPUBLIC
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* This function destroys a condition variable
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*
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*
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* PARAMETERS
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* cond
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* pointer to an instance of pthread_cond_t
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*
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*
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* DESCRIPTION
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* This function destroys a condition variable.
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*
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* NOTES:
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* 1) A condition variable can be destroyed
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* immediately after all the threads that
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* are blocked on it are awakened. e.g.
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*
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* struct list {
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* pthread_mutex_t lm;
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* ...
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* }
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*
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* struct elt {
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* key k;
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* int busy;
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* pthread_cond_t notbusy;
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* ...
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* }
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*
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*
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* struct elt *
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* list_find(struct list *lp, key k)
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* {
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* struct elt *ep;
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*
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* pthread_mutex_lock(&lp->lm);
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* while ((ep = find_elt(l,k) != NULL) && ep->busy)
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* pthread_cond_wait(&ep->notbusy, &lp->lm);
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* if (ep != NULL)
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* ep->busy = 1;
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* pthread_mutex_unlock(&lp->lm);
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* return(ep);
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* }
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*
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* delete_elt(struct list *lp, struct elt *ep)
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* {
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* pthread_mutex_lock(&lp->lm);
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* assert(ep->busy);
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* ... remove ep from list ...
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* ep->busy = 0;
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* (A) pthread_cond_broadcast(&ep->notbusy);
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* pthread_mutex_unlock(&lp->lm);
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* (B) pthread_cond_destroy(&rp->notbusy);
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* free(ep);
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* }
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*
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* In this example, the condition variable
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* and its list element may be freed (line B)
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* immediately after all threads waiting for
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* it are awakened (line A), since the mutex
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* and the code ensure that no other thread
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* can touch the element to be deleted.
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*
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* RESULTS
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* 0 successfully released condition variable,
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* EINVAL 'cond' is invalid,
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* EBUSY 'cond' is in use,
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*
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* ------------------------------------------------------
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*/
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{
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pthread_cond_t cv;
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int result = 0, result1 = 0, result2 = 0;
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/*
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* Assuming any race condition here is harmless.
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*/
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if (cond == NULL || *cond == NULL)
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{
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return EINVAL;
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}
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if (*cond != PTHREAD_COND_INITIALIZER)
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{
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ptw32_mcs_local_node_t node;
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ptw32_mcs_lock_acquire(&ptw32_cond_list_lock, &node);
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cv = *cond;
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/*
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* Close the gate; this will synchronize this thread with
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* all already signaled waiters to let them retract their
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* waiter status - SEE NOTE 1 ABOVE!!!
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*/
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if (ptw32_semwait (&(cv->semBlockLock)) != 0) /* Non-cancelable */
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{
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result = errno;
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}
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else
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{
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/*
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* !TRY! lock mtxUnblockLock; try will detect busy condition
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* and will not cause a deadlock with respect to concurrent
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* signal/broadcast.
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*/
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if ((result = pthread_mutex_trylock (&(cv->mtxUnblockLock))) != 0)
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{
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(void) sem_post (&(cv->semBlockLock));
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}
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}
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if (result != 0)
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{
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ptw32_mcs_lock_release(&node);
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return result;
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}
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/*
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* Check whether cv is still busy (still has waiters)
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*/
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if (cv->nWaitersBlocked > cv->nWaitersGone)
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{
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if (sem_post (&(cv->semBlockLock)) != 0)
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{
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result = errno;
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}
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result1 = pthread_mutex_unlock (&(cv->mtxUnblockLock));
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result2 = EBUSY;
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}
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else
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{
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/*
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* Now it is safe to destroy
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*/
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*cond = NULL;
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if (sem_destroy (&(cv->semBlockLock)) != 0)
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{
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result = errno;
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}
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if (sem_destroy (&(cv->semBlockQueue)) != 0)
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{
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result1 = errno;
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}
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if ((result2 = pthread_mutex_unlock (&(cv->mtxUnblockLock))) == 0)
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{
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result2 = pthread_mutex_destroy (&(cv->mtxUnblockLock));
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}
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/* Unlink the CV from the list */
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if (ptw32_cond_list_head == cv)
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{
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ptw32_cond_list_head = cv->next;
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}
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else
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{
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cv->prev->next = cv->next;
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}
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if (ptw32_cond_list_tail == cv)
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{
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ptw32_cond_list_tail = cv->prev;
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}
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else
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{
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cv->next->prev = cv->prev;
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}
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(void) free (cv);
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}
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ptw32_mcs_lock_release(&node);
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}
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else
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{
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ptw32_mcs_local_node_t node;
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/*
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* See notes in ptw32_cond_check_need_init() above also.
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*/
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ptw32_mcs_lock_acquire(&ptw32_cond_test_init_lock, &node);
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/*
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* Check again.
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*/
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if (*cond == PTHREAD_COND_INITIALIZER)
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{
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/*
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* This is all we need to do to destroy a statically
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* initialised cond that has not yet been used (initialised).
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* If we get to here, another thread waiting to initialise
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* this cond will get an EINVAL. That's OK.
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*/
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*cond = NULL;
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}
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else
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{
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/*
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* The cv has been initialised while we were waiting
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* so assume it's in use.
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*/
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result = EBUSY;
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}
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ptw32_mcs_lock_release(&node);
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}
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return ((result != 0) ? result : ((result1 != 0) ? result1 : result2));
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}
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