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71 lines
1.9 KiB
C
71 lines
1.9 KiB
C
/* Post a semaphore. Generic version.
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Copyright (C) 2005-2023 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#include <semaphore.h>
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#include <assert.h>
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#include <hurdlock.h>
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#include <pt-internal.h>
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int
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__sem_post (sem_t *sem)
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{
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struct new_sem *isem = (struct new_sem *) sem;
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int flags = isem->pshared ? GSYNC_SHARED : 0;
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#if __HAVE_64B_ATOMICS
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uint64_t d = atomic_load_relaxed (&isem->data);
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do
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{
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if ((d & SEM_VALUE_MASK) == SEM_VALUE_MAX)
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{
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errno = EOVERFLOW;
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return -1;
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}
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}
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while (!atomic_compare_exchange_weak_release (&isem->data, &d, d + 1));
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if ((d >> SEM_NWAITERS_SHIFT) != 0)
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/* Wake one waiter. */
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__lll_wake (((unsigned int *) &isem->data) + SEM_VALUE_OFFSET, flags);
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#else
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unsigned int v = atomic_load_relaxed (&isem->value);
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do
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{
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if ((v >> SEM_VALUE_SHIFT) == SEM_VALUE_MAX)
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{
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errno = EOVERFLOW;
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return -1;
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}
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}
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while (!atomic_compare_exchange_weak_release
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(&isem->value, &v, v + (1 << SEM_VALUE_SHIFT)));
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if ((v & SEM_NWAITERS_MASK) != 0)
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/* Wake one waiter. */
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__lll_wake (&isem->value, flags);
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#endif
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return 0;
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}
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libpthread_hidden_def (__sem_post)
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strong_alias (__sem_post, sem_post);
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