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/* Post a semaphore. Generic version.
Copyright (C) 2005-2025 Free Software Foundation, Inc.
This file is part of the GNU C Library.
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
<https://www.gnu.org/licenses/>. */
#include <semaphore.h>
#include <assert.h>
#include <hurdlock.h>
#include <hurd.h>
#include <pt-internal.h>
int
__sem_post (sem_t *sem)
{
struct new_sem *isem = (struct new_sem *) sem;
int flags = isem->pshared ? GSYNC_SHARED : 0;
#if __HAVE_64B_ATOMICS
uint64_t d = atomic_load_relaxed (&isem->data);
do
{
if ((d & SEM_VALUE_MASK) == SEM_VALUE_MAX)
return __hurd_fail (EOVERFLOW);
}
while (!atomic_compare_exchange_weak_release (&isem->data, &d, d + 1));
if ((d >> SEM_NWAITERS_SHIFT) != 0)
/* Wake one waiter. */
__lll_wake (((unsigned int *) &isem->data) + SEM_VALUE_OFFSET, flags);
#else
unsigned int v = atomic_load_relaxed (&isem->value);
do
{
if ((v >> SEM_VALUE_SHIFT) == SEM_VALUE_MAX)
return __hurd_fail (EOVERFLOW);
}
while (!atomic_compare_exchange_weak_release
(&isem->value, &v, v + (1 << SEM_VALUE_SHIFT)));
if ((v & SEM_NWAITERS_MASK) != 0)
/* Wake one waiter. */
__lll_wake (&isem->value, flags);
#endif
return 0;
}
libpthread_hidden_def (__sem_post)
strong_alias (__sem_post, sem_post);
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