nptl/pthread_cond_wait.c

   1 /* Copyright (C) 2002 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, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 #include "pthreadP.h"
  21 #include <lowlevellock.h>
  22
  23
  24 int
  25 pthread_cond_wait (cond, mutex)
  26      pthread_cond_t *cond;
  27      pthread_mutex_t *mutex;
  28 {
  29   int err;
  30
  31   /* This function is a cancellation point.  Test before we potentially
  32      go to sleep.  */
  33   CANCELLATION_P (THREAD_SELF);
  34
  35   /* Make sure the condition is modified atomically.  */
  36   lll_mutex_lock (cond->__data.__lock);
  37
  38   /* Release the mutex.  This might fail.  */
  39   err = pthread_mutex_unlock (mutex);
  40   if (__builtin_expect (err != 0, 0))
  41     {
  42       lll_mutex_unlock (cond->__data.__lock);
  43       return err;
  44     }
  45
  46   /* One more tread waiting.  */
  47   ++cond->__data.__nr_sleepers;
  48
  49   /* The actual conditional variable implementation.  */
  50   lll_cond_wait (cond);
  51
  52   if (--cond->__data.__nr_sleepers == 0)
  53     /* Forget about the current wakeups now that they are done.  */
  54     cond->__data.__nr_wakers = 0;
  55
  56   /* Lose the condvar lock.  */
  57   lll_mutex_unlock (cond->__data.__lock);
  58
  59   /* We have to get the mutex before returning.  */
  60   err = pthread_mutex_lock (mutex);
  61
  62   /* Cancellation handling.  */
  63   CANCELLATION_P (THREAD_SELF);
  64
  65   return err;
  66 }