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/* Lock a semaphore if it does not require blocking. Generic version.
Copyright (C) 2005-2020 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 <errno.h>
#include <pt-internal.h>
int
__sem_waitfast (struct new_sem *isem, int definitive_result)
{
#if __HAVE_64B_ATOMICS
uint64_t d = atomic_load_relaxed (&isem->data);
do
{
if ((d & SEM_VALUE_MASK) == 0)
break;
if (atomic_compare_exchange_weak_acquire (&isem->data, &d, d - 1))
/* Successful down. */
return 0;
}
while (definitive_result);
return -1;
#else
unsigned v = atomic_load_relaxed (&isem->value);
do
{
if ((v >> SEM_VALUE_SHIFT) == 0)
break;
if (atomic_compare_exchange_weak_acquire (&isem->value,
&v, v - (1 << SEM_VALUE_SHIFT)))
/* Successful down. */
return 0;
}
while (definitive_result);
return -1;
#endif
}
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