nptl/pthread_cond_destroy.c

   1 /* Copyright (C) 2002-2016 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 <shlib-compat.h>
  21 #include "pthreadP.h"
  22 #include <stap-probe.h>
  23
  24
  25 int
  26 __pthread_cond_destroy (pthread_cond_t *cond)
  27 {
  28   int pshared = (cond->__data.__mutex == (void *) ~0l)
  29                 ? LLL_SHARED : LLL_PRIVATE;
  30
  31   LIBC_PROBE (cond_destroy, 1, cond);
  32
  33   /* Make sure we are alone.  */
  34   lll_lock (cond->__data.__lock, pshared);
  35
  36   if (cond->__data.__total_seq > cond->__data.__wakeup_seq)
  37     {
  38       /* If there are still some waiters which have not been
  39          woken up, this is an application bug.  */
  40       lll_unlock (cond->__data.__lock, pshared);
  41       return EBUSY;
  42     }
  43
  44   /* Tell pthread_cond_*wait that this condvar is being destroyed.  */
  45   cond->__data.__total_seq = -1ULL;
  46
  47   /* If there are waiters which have been already signalled or
  48      broadcasted, but still are using the pthread_cond_t structure,
  49      pthread_cond_destroy needs to wait for them.  */
  50   unsigned int nwaiters = cond->__data.__nwaiters;
  51
  52   if (nwaiters >= (1 << COND_NWAITERS_SHIFT))
  53     {
  54       /* Wake everybody on the associated mutex in case there are
  55          threads that have been requeued to it.
  56          Without this, pthread_cond_destroy could block potentially
  57          for a long time or forever, as it would depend on other
  58          thread's using the mutex.
  59          When all threads waiting on the mutex are woken up, pthread_cond_wait
  60          only waits for threads to acquire and release the internal
  61          condvar lock.  */
  62       if (cond->__data.__mutex != NULL
  63           && cond->__data.__mutex != (void *) ~0l)
  64         {
  65           pthread_mutex_t *mut = (pthread_mutex_t *) cond->__data.__mutex;
  66           lll_futex_wake (&mut->__data.__lock, INT_MAX,
  67                           PTHREAD_MUTEX_PSHARED (mut));
  68         }
  69
  70       do
  71         {
  72           lll_unlock (cond->__data.__lock, pshared);
  73
  74           lll_futex_wait (&cond->__data.__nwaiters, nwaiters, pshared);
  75
  76           lll_lock (cond->__data.__lock, pshared);
  77
  78           nwaiters = cond->__data.__nwaiters;
  79         }
  80       while (nwaiters >= (1 << COND_NWAITERS_SHIFT));
  81     }
  82
  83   return 0;
  84 }
  85 versioned_symbol (libpthread, __pthread_cond_destroy,
  86                   pthread_cond_destroy, GLIBC_2_3_2);