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147 lines
3.6 KiB
C
147 lines
3.6 KiB
C
/* sem_waitcommon -- wait on a semaphore, shared code.
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Copyright (C) 2003-2017 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Paul Mackerras <paulus@au.ibm.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 <errno.h>
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#include <sysdep.h>
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#include <futex-internal.h>
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#include <internaltypes.h>
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#include <semaphore.h>
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#include <sys/time.h>
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#include <pthreadP.h>
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#include <shlib-compat.h>
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#include <atomic.h>
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static void
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__sem_wait_32_finish (struct new_sem *sem);
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static void
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__sem_wait_cleanup (void *arg)
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{
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struct new_sem *sem = (struct new_sem *) arg;
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__sem_wait_32_finish (sem);
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}
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/* Wait until at least one token is available, possibly with a timeout.
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This is in a separate function in order to make sure gcc
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puts the call site into an exception region, and thus the
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cleanups get properly run. TODO still necessary? Other futex_wait
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users don't seem to need it. */
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static int
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__attribute__ ((noinline))
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do_futex_wait (struct new_sem *sem, const struct timespec *abstime)
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{
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int err;
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err = futex_abstimed_wait_cancelable (&sem->value, SEM_NWAITERS_MASK,
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abstime, sem->private);
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return err;
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}
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/* Fast path: Try to grab a token without blocking. */
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static int
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__new_sem_wait_fast (struct new_sem *sem, int definitive_result)
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{
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unsigned int v;
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int ret = 0;
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__sparc32_atomic_do_lock24(&sem->pad);
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v = sem->value;
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if ((v >> SEM_VALUE_SHIFT) == 0)
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ret = -1;
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else
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sem->value = v - (1 << SEM_VALUE_SHIFT);
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__sparc32_atomic_do_unlock24(&sem->pad);
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return ret;
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}
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/* Slow path that blocks. */
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static int
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__attribute__ ((noinline))
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__new_sem_wait_slow (struct new_sem *sem, const struct timespec *abstime)
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{
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unsigned int v;
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int err = 0;
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__sparc32_atomic_do_lock24(&sem->pad);
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sem->nwaiters++;
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pthread_cleanup_push (__sem_wait_cleanup, sem);
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/* Wait for a token to be available. Retry until we can grab one. */
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v = sem->value;
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do
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{
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if (!(v & SEM_NWAITERS_MASK))
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sem->value = v | SEM_NWAITERS_MASK;
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/* If there is no token, wait. */
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if ((v >> SEM_VALUE_SHIFT) == 0)
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{
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__sparc32_atomic_do_unlock24(&sem->pad);
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err = do_futex_wait(sem, abstime);
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if (err == ETIMEDOUT || err == EINTR)
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{
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__set_errno (err);
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err = -1;
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goto error;
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}
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err = 0;
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__sparc32_atomic_do_lock24(&sem->pad);
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/* We blocked, so there might be a token now. */
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v = sem->value;
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}
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}
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/* If there is no token, we must not try to grab one. */
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while ((v >> SEM_VALUE_SHIFT) == 0);
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sem->value = v - (1 << SEM_VALUE_SHIFT);
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__sparc32_atomic_do_unlock24(&sem->pad);
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error:
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pthread_cleanup_pop (0);
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__sem_wait_32_finish (sem);
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return err;
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}
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/* Stop being a registered waiter (non-64b-atomics code only). */
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static void
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__sem_wait_32_finish (struct new_sem *sem)
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{
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__sparc32_atomic_do_lock24(&sem->pad);
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if (--sem->nwaiters == 0)
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sem->value &= ~SEM_NWAITERS_MASK;
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__sparc32_atomic_do_unlock24(&sem->pad);
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}
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