libpthread/nptl/pthread_cond_destroy.c

   1 /* Copyright (C) 2002, 2003, 2004, 2007 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <errno.h>
  20 #include "pthreadP.h"
  21
  22
  23 int
  24 attribute_protected
  25 __pthread_cond_destroy (
  26      pthread_cond_t *cond)
  27 {
  28   int pshared = (cond->__data.__mutex == (void *) ~0l)
  29                 ? LLL_SHARED : LLL_PRIVATE;
  30
  31   /* Make sure we are alone.  */
  32   lll_lock (cond->__data.__lock, pshared);
  33
  34   if (cond->__data.__total_seq > cond->__data.__wakeup_seq)
  35     {
  36       /* If there are still some waiters which have not been
  37          woken up, this is an application bug.  */
  38       lll_unlock (cond->__data.__lock, pshared);
  39       return EBUSY;
  40     }
  41
  42   /* Tell pthread_cond_*wait that this condvar is being destroyed.  */
  43   cond->__data.__total_seq = -1ULL;
  44
  45   /* If there are waiters which have been already signalled or
  46      broadcasted, but still are using the pthread_cond_t structure,
  47      pthread_cond_destroy needs to wait for them.  */
  48   unsigned int nwaiters = cond->__data.__nwaiters;
  49
  50   if (nwaiters >= (1 << COND_NWAITERS_SHIFT))
  51     {
  52       /* Wake everybody on the associated mutex in case there are
  53          threads that have been requeued to it.
  54          Without this, pthread_cond_destroy could block potentially
  55          for a long time or forever, as it would depend on other
  56          thread's using the mutex.
  57          When all threads waiting on the mutex are woken up, pthread_cond_wait
  58          only waits for threads to acquire and release the internal
  59          condvar lock.  */
  60       if (cond->__data.__mutex != NULL
  61           && cond->__data.__mutex != (void *) ~0l)
  62         {
  63           pthread_mutex_t *mut = (pthread_mutex_t *) cond->__data.__mutex;
  64           lll_futex_wake (&mut->__data.__lock, INT_MAX,
  65                           PTHREAD_MUTEX_PSHARED (mut));
  66         }
  67
  68       do
  69         {
  70           lll_unlock (cond->__data.__lock, pshared);
  71
  72           lll_futex_wait (&cond->__data.__nwaiters, nwaiters, pshared);
  73
  74           lll_lock (cond->__data.__lock, pshared);
  75
  76           nwaiters = cond->__data.__nwaiters;
  77         }
  78       while (nwaiters >= (1 << COND_NWAITERS_SHIFT));
  79     }
  80
  81   return 0;
  82 }
  83 weak_alias(__pthread_cond_destroy, pthread_cond_destroy)