/* sem_wait -- wait on a semaphore.  Generic futex-using version.

   Copyright (C) 2003-2018 Free Software Foundation, Inc.

   This file is part of the GNU C Library.

   Contributed by Paul Mackerras <paulus@au.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 <lowlevellock.h>	/* lll_futex* used by the old code.  */

#include "sem_waitcommon.c"

int

__new_sem_wait (sem_t *sem)

{

  /* We need to check whether we need to act upon a cancellation request here

     because POSIX specifies that cancellation points "shall occur" in

     sem_wait and sem_timedwait, which also means that they need to check

     this regardless whether they block or not (unlike "may occur"

     functions).  See the POSIX Rationale for this requirement: Section

     "Thread Cancellation Overview" [1] and austin group issue #1076 [2]

     for thoughs on why this may be a suboptimal design.

     [1] http://pubs.opengroup.org/onlinepubs/9699919799/xrat/V4_xsh_chap02.html

     [2] http://austingroupbugs.net/view.php?id=1076 for thoughts on why this

   */

  __pthread_testcancel ();

  if (__new_sem_wait_fast ((struct new_sem *) sem, 0) == 0)

    return 0;

  else

    return __new_sem_wait_slow((struct new_sem *) sem, NULL);

}

versioned_symbol (libpthread, __new_sem_wait, sem_wait, GLIBC_2_1);

#if SHLIB_COMPAT (libpthread, GLIBC_2_0, GLIBC_2_1)

int

attribute_compat_text_section

__old_sem_wait (sem_t *sem)

{

  int *futex = (int *) sem;

  int err;

  do

    {

      if (atomic_decrement_if_positive (futex) > 0)

	return 0;

      /* Enable asynchronous cancellation.  Required by the standard.  */

      int oldtype = __pthread_enable_asynccancel ();

      /* Always assume the semaphore is shared.  */

      err = lll_futex_wait (futex, 0, LLL_SHARED);

      /* Disable asynchronous cancellation.  */

      __pthread_disable_asynccancel (oldtype);

    }

  while (err == 0 || err == -EWOULDBLOCK);

  __set_errno (-err);

  return -1;

}

compat_symbol (libpthread, __old_sem_wait, sem_wait, GLIBC_2_0);

#endif

int

__new_sem_trywait (sem_t *sem)

{

  /* We must not fail spuriously, so require a definitive result even if this

     may lead to a long execution time.  */

  if (__new_sem_wait_fast ((struct new_sem *) sem, 1) == 0)

    return 0;

  __set_errno (EAGAIN);

  return -1;

}

versioned_symbol (libpthread, __new_sem_trywait, sem_trywait, GLIBC_2_1);

#if SHLIB_COMPAT (libpthread, GLIBC_2_0, GLIBC_2_1)

int

__old_sem_trywait (sem_t *sem)

{

  int *futex = (int *) sem;

  int val;

  if (*futex > 0)

    {

      val = atomic_decrement_if_positive (futex);

      if (val > 0)

	return 0;

    }

  __set_errno (EAGAIN);

  return -1;

}

compat_symbol (libpthread, __old_sem_trywait, sem_trywait, GLIBC_2_0);

#endif