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/*
* 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));
}
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