[thirdparty/glibc.git] / nptl / pthread_cond_signal.c

/* Copyright (C) 2003-2016 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>
#include <stap-probe.h>


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

  LIBC_PROBE (cond_signal, 1, cond);

  /* 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;

#if (defined lll_futex_cmp_requeue_pi \
     && defined __ASSUME_REQUEUE_PI)
      pthread_mutex_t *mut = cond->__data.__mutex;

      if (USE_REQUEUE_PI (mut)
	/* This can only really fail with a ENOSYS, since nobody can modify
	   futex while we have the cond_lock.  */
	  && lll_futex_cmp_requeue_pi (&cond->__data.__futex, 1, 0,
				       &mut->__data.__lock,
				       cond->__data.__futex, pshared) == 0)
	{
	  lll_unlock (cond->__data.__lock, pshared);
	  return 0;
	}
      else
#endif
	/* Wake one.  */
	if (! __builtin_expect (lll_futex_wake_unlock (&cond->__data.__futex,
						       1, 1,
						       &cond->__data.__lock,
						       pshared), 0))
	  return 0;

      /* Fallback if neither of them work.  */
      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);
Commit	Line	Data
f7a9f785	1	/* Copyright (C) 2003-2016 Free Software Foundation, Inc.
a88c9263 UD	2	This file is part of the GNU C Library.
	3	Contributed by Martin Schwidefsky <schwidefsky@de.ibm.com>, 2003.
	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
59ba27a6 PE	16	License along with the GNU C Library; if not, see
59ba27a6 PE	17	<http://www.gnu.org/licenses/>. */
a88c9263 UD	18
	19	#include <endian.h>
	20	#include <errno.h>
	21	#include <sysdep.h>
	22	#include <lowlevellock.h>
	23	#include <pthread.h>
	24	#include <pthreadP.h>
	25
	26	#include <shlib-compat.h>
69431c9a	27	#include <kernel-features.h>
5acf7263	28	#include <stap-probe.h>
69431c9a	29
a88c9263 UD	30
a88c9263 UD	31	int
9d46370c	32	__pthread_cond_signal (pthread_cond_t *cond)
a88c9263	33	{
5bd8a249 UD	34	int pshared = (cond->__data.__mutex == (void *) ~0l)
	35	? LLL_SHARED : LLL_PRIVATE;
	36
5acf7263 RM	37	LIBC_PROBE (cond_signal, 1, cond);
5acf7263 RM	38
a88c9263	39	/* Make sure we are alone. */
5bd8a249	40	lll_lock (cond->__data.__lock, pshared);
a88c9263 UD	41
	42	/* Are there any waiters to be woken? */
	43	if (cond->__data.__total_seq > cond->__data.__wakeup_seq)
	44	{
	45	/* Yes. Mark one of them as woken. */
	46	++cond->__data.__wakeup_seq;
75fccede	47	++cond->__data.__futex;
a88c9263	48
8313cb99 SP	49	#if (defined lll_futex_cmp_requeue_pi \
8313cb99 SP	50	&& defined __ASSUME_REQUEUE_PI)
8313cb99	51	pthread_mutex_t *mut = cond->__data.__mutex;
a3615024	52
ad4e70da	53	if (USE_REQUEUE_PI (mut)
8313cb99 SP	54	/* This can only really fail with a ENOSYS, since nobody can modify
	55	futex while we have the cond_lock. */
	56	&& lll_futex_cmp_requeue_pi (&cond->__data.__futex, 1, 0,
	57	&mut->__data.__lock,
	58	cond->__data.__futex, pshared) == 0)
	59	{
	60	lll_unlock (cond->__data.__lock, pshared);
	61	return 0;
	62	}
	63	else
	64	#endif
	65	/* Wake one. */
	66	if (! __builtin_expect (lll_futex_wake_unlock (&cond->__data.__futex,
	67	1, 1,
	68	&cond->__data.__lock,
	69	pshared), 0))
	70	return 0;
	71
	72	/* Fallback if neither of them work. */
5bd8a249	73	lll_futex_wake (&cond->__data.__futex, 1, pshared);
a88c9263 UD	74	}
	75
	76	/* We are done. */
5bd8a249	77	lll_unlock (cond->__data.__lock, pshared);
a88c9263 UD	78
	79	return 0;
	80	}
	81
	82	versioned_symbol (libpthread, __pthread_cond_signal, pthread_cond_signal,
	83	GLIBC_2_3_2);