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/* sem_post -- post to a POSIX semaphore. Generic futex-using version.
Copyright (C) 2003-2015 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Jakub Jelinek <jakub@redhat.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 <atomic.h>
#include <errno.h>
#include <sysdep.h>
#include <lowlevellock.h>
#include <internaltypes.h>
#include <semaphore.h>
#include <shlib-compat.h>
/* Wrapper for lll_futex_wake, with error checking.
TODO Remove when cleaning up the futex API throughout glibc. */
static __always_inline void
futex_wake (unsigned int* futex, int processes_to_wake, int private)
{
int res = lll_futex_wake (futex, processes_to_wake, private);
/* No error. Ignore the number of woken processes. */
if (res >= 0)
return;
switch (res)
{
case -EFAULT: /* Could have happened due to memory reuse. */
case -EINVAL: /* Could be either due to incorrect alignment (a bug in
glibc or in the application) or due to memory being
reused for a PI futex. We cannot distinguish between the
two causes, and one of them is correct use, so we do not
act in this case. */
return;
case -ENOSYS: /* Must have been caused by a glibc bug. */
/* No other errors are documented at this time. */
default:
abort ();
}
}
/* See sem_wait for an explanation of the algorithm. */
int
__new_sem_post (sem_t *sem)
{
struct new_sem *isem = (struct new_sem *) sem;
int private = isem->private;
unsigned int v;
__sparc32_atomic_do_lock24(&isem->pad);
v = isem->value;
if ((v << SEM_VALUE_SHIFT) == SEM_VALUE_MAX)
{
__sparc32_atomic_do_unlock24(&isem->pad);
__set_errno (EOVERFLOW);
return -1;
}
isem->value = v + (1 << SEM_VALUE_SHIFT);
__sparc32_atomic_do_unlock24(&isem->pad);
if ((v & SEM_NWAITERS_MASK) != 0)
futex_wake (&isem->value, 1, private);
return 0;
}
versioned_symbol (libpthread, __new_sem_post, sem_post, GLIBC_2_1);
#if SHLIB_COMPAT (libpthread, GLIBC_2_0, GLIBC_2_1)
int
attribute_compat_text_section
__old_sem_post (sem_t *sem)
{
int *futex = (int *) sem;
/* We must need to synchronize with consumers of this token, so the atomic
increment must have release MO semantics. */
atomic_write_barrier ();
(void) atomic_increment_val (futex);
/* We always have to assume it is a shared semaphore. */
int err = lll_futex_wake (futex, 1, LLL_SHARED);
if (__builtin_expect (err, 0) < 0)
{
__set_errno (-err);
return -1;
}
return 0;
}
compat_symbol (libpthread, __old_sem_post, sem_post, GLIBC_2_0);
#endif
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