sem_wait.c

glibc 2.9,最新版的C语言库函数

/* sem_wait -- wait on a semaphore.  Generic futex-using version.
   Copyright (C) 2003, 2007 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Paul Mackerras <[e-mail]>, 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, write to the Free
   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   02111-1307 USA.  */

#include <errno.h>
#include <sysdep.h>
#include <lowlevellock.h>
#include <internaltypes.h>
#include <semaphore.h>

#include <pthreadP.h>
#include <shlib-compat.h>


void
attribute_hidden
__sem_wait_cleanup (void *arg)
{
  struct sparc_new_sem *isem = (struct sparc_new_sem *) arg;

  if (__atomic_is_v9)
    atomic_decrement (&isem->nwaiters);
  else
    {
      __sparc32_atomic_do_lock24 (&isem->lock);
      isem->nwaiters--;
      __sparc32_atomic_do_unlock24 (&isem->lock);
    }
}


int
__new_sem_wait (sem_t *sem)
{
  struct sparc_new_sem *isem = (struct sparc_new_sem *) sem;
  int err;
  int val;

  if (__atomic_is_v9)
    val = atomic_decrement_if_positive (&isem->value);
  else
    {
      __sparc32_atomic_do_lock24 (&isem->lock);
      val = isem->value;
      if (val > 0)
	isem->value = val - 1;
      else
	isem->nwaiters++;
      __sparc32_atomic_do_unlock24 (&isem->lock);
    }

  if (val > 0)
    return 0;

  if (__atomic_is_v9)
    atomic_increment (&isem->nwaiters);
  else
    /* Already done above while still holding isem->lock.  */;

  pthread_cleanup_push (__sem_wait_cleanup, isem);

  while (1)
    {
      /* Enable asynchronous cancellation.  Required by the standard.  */
      int oldtype = __pthread_enable_asynccancel ();

      err = lll_futex_wait (&isem->value, 0,
			    isem->private ^ FUTEX_PRIVATE_FLAG);

      /* Disable asynchronous cancellation.  */
      __pthread_disable_asynccancel (oldtype);

      if (err != 0 && err != -EWOULDBLOCK)
	{
	  __set_errno (-err);
	  err = -1;
	  break;
	}

      if (__atomic_is_v9)
	val = atomic_decrement_if_positive (&isem->value);
      else
	{
	  __sparc32_atomic_do_lock24 (&isem->lock);
	  val = isem->value;
	  if (val > 0)
	    isem->value = val - 1;
	  __sparc32_atomic_do_unlock24 (&isem->lock);
	}

      if (val > 0)
	{
	  err = 0;
	  break;
	}
    }

  pthread_cleanup_pop (0);

  if (__atomic_is_v9)
    atomic_decrement (&isem->nwaiters);
  else
    {
      __sparc32_atomic_do_lock24 (&isem->lock);
      isem->nwaiters--;
      __sparc32_atomic_do_unlock24 (&isem->lock);
    }

  return err;
}
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)
{
  struct sparc_old_sem *isem = (struct sparc_old_sem *) sem;
  int err;
  int val;

  do
    {
      if (__atomic_is_v9)
	val = atomic_decrement_if_positive (&isem->value);
      else
	{
	  __sparc32_atomic_do_lock24 (&isem->lock);
	  val = isem->value;
	  if (val > 0)
	    isem->value = val - 1;
	  __sparc32_atomic_do_unlock24 (&isem->lock);
	}

      if (val > 0)
	return 0;

      /* Enable asynchronous cancellation.  Required by the standard.  */
      int oldtype = __pthread_enable_asynccancel ();

      err = lll_futex_wait (&isem->value, 0,
			    isem->private ^ FUTEX_PRIVATE_FLAG);

      /* 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