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/* sem_waitcommon -- wait on a semaphore, shared code.
Copyright (C) 2003-2019 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Paul Mackerras <paulus@au.ibm.com>, 2003.
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 <errno.h>
#include <sysdep.h>
#include <futex-internal.h>
#include <internaltypes.h>
#include <semaphore.h>
#include <sys/time.h>
#include <pthreadP.h>
#include <shlib-compat.h>
#include <atomic.h>
static void
__sem_wait_32_finish (struct new_sem *sem);
static void
__sem_wait_cleanup (void *arg)
{
struct new_sem *sem = (struct new_sem *) arg;
__sem_wait_32_finish (sem);
}
/* Wait until at least one token is available, possibly with a timeout.
This is in a separate function in order to make sure gcc
puts the call site into an exception region, and thus the
cleanups get properly run. TODO still necessary? Other futex_wait
users don't seem to need it. */
static int
__attribute__ ((noinline))
do_futex_wait (struct new_sem *sem, const struct timespec *abstime)
{
int err;
err = futex_abstimed_wait_cancelable (&sem->value, SEM_NWAITERS_MASK,
abstime, sem->private);
return err;
}
/* Fast path: Try to grab a token without blocking. */
static int
__new_sem_wait_fast (struct new_sem *sem, int definitive_result)
{
unsigned int v;
int ret = 0;
__sparc32_atomic_do_lock24(&sem->pad);
v = sem->value;
if ((v >> SEM_VALUE_SHIFT) == 0)
ret = -1;
else
sem->value = v - (1 << SEM_VALUE_SHIFT);
__sparc32_atomic_do_unlock24(&sem->pad);
return ret;
}
/* Slow path that blocks. */
static int
__attribute__ ((noinline))
__new_sem_wait_slow (struct new_sem *sem, const struct timespec *abstime)
{
unsigned int v;
int err = 0;
__sparc32_atomic_do_lock24(&sem->pad);
sem->nwaiters++;
pthread_cleanup_push (__sem_wait_cleanup, sem);
/* Wait for a token to be available. Retry until we can grab one. */
v = sem->value;
do
{
if (!(v & SEM_NWAITERS_MASK))
sem->value = v | SEM_NWAITERS_MASK;
/* If there is no token, wait. */
if ((v >> SEM_VALUE_SHIFT) == 0)
{
__sparc32_atomic_do_unlock24(&sem->pad);
err = do_futex_wait(sem, abstime);
if (err == ETIMEDOUT || err == EINTR)
{
__set_errno (err);
err = -1;
goto error;
}
err = 0;
__sparc32_atomic_do_lock24(&sem->pad);
/* We blocked, so there might be a token now. */
v = sem->value;
}
}
/* If there is no token, we must not try to grab one. */
while ((v >> SEM_VALUE_SHIFT) == 0);
sem->value = v - (1 << SEM_VALUE_SHIFT);
__sparc32_atomic_do_unlock24(&sem->pad);
error:
pthread_cleanup_pop (0);
__sem_wait_32_finish (sem);
return err;
}
/* Stop being a registered waiter (non-64b-atomics code only). */
static void
__sem_wait_32_finish (struct new_sem *sem)
{
__sparc32_atomic_do_lock24(&sem->pad);
if (--sem->nwaiters == 0)
sem->value &= ~SEM_NWAITERS_MASK;
__sparc32_atomic_do_unlock24(&sem->pad);
}
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