glibc/nptl/pthread_cond_signal.c

/* Copyright (C) 2003, 2004, 2007 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Martin Schwidefsky <schwidefsky@de.ibm.com>, 2003.

   The GNU C 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 2.1 of the License, or (at your option) any later version.

   The GNU C 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 the GNU C Library; if not, see
   <http://www.gnu.org/licenses/>.  */

#include <endian.h>
#include <errno.h>
#include <sysdep.h>
#include <lowlevellock.h>
#include <pthread.h>
#include <pthreadP.h>

#include <shlib-compat.h>
#include <kernel-features.h>


int
__pthread_cond_signal (cond)
     pthread_cond_t *cond;
{
  int pshared = (cond->__data.__mutex == (void *) ~0l)
		? LLL_SHARED : LLL_PRIVATE;

  /* Make sure we are alone.  */
  lll_lock (cond->__data.__lock, pshared);

  /* Are there any waiters to be woken?  */
  if (cond->__data.__total_seq > cond->__data.__wakeup_seq)
    {
      /* Yes.  Mark one of them as woken.  */
      ++cond->__data.__wakeup_seq;
      ++cond->__data.__futex;

      /* Wake one.  */
      if (! __builtin_expect (lll_futex_wake_unlock (&cond->__data.__futex, 1,
						     1, &cond->__data.__lock,
						     pshared), 0))
	return 0;

      lll_futex_wake (&cond->__data.__futex, 1, pshared);
    }

  /* We are done.  */
  lll_unlock (cond->__data.__lock, pshared);

  return 0;
}

versioned_symbol (libpthread, __pthread_cond_signal, pthread_cond_signal,
		  GLIBC_2_3_2);