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