/* * pthread_cond_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) 1999,2005 Pthreads-win32 contributors *  *      Contact Email: rpj@callisto.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"intpthread_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)    {      EnterCriticalSection (&ptw32_cond_list_lock);      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 cause 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));	    }	  /* Unlink the CV from the list */	  if (ptw32_cond_list_head == cv)	    {	      ptw32_cond_list_head = cv->next;	    }	  else	    {	      cv->prev->next = cv->next;	    }	  if (ptw32_cond_list_tail == cv)	    {	      ptw32_cond_list_tail = cv->prev;	    }	  else	    {	      cv->next->prev = cv->prev;	    }	  (void) free (cv);	}      LeaveCriticalSection (&ptw32_cond_list_lock);    }  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));}