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/* Wait on a semaphore with a timeout. Generic version.
Copyright (C) 2005-2025 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 <assert.h>
#include <time.h>
#include <hurdlock.h>
#include <hurd/hurd.h>
#include <sysdep-cancel.h>
#include <pt-internal.h>
#if !__HAVE_64B_ATOMICS
static void
__sem_wait_32_finish (struct new_sem *isem);
#endif
static void
__sem_wait_cleanup (void *arg)
{
struct new_sem *isem = arg;
#if __HAVE_64B_ATOMICS
atomic_fetch_add_relaxed (&isem->data, -((uint64_t) 1 << SEM_NWAITERS_SHIFT));
#else
__sem_wait_32_finish (isem);
#endif
}
int
__sem_timedwait_internal (sem_t *restrict sem,
clockid_t clock_id,
const struct timespec *restrict timeout)
{
struct new_sem *isem = (struct new_sem *) sem;
int err, ret = 0;
int flags = isem->pshared ? GSYNC_SHARED : 0;
__pthread_testcancel ();
if (__sem_waitfast (isem, 0) == 0)
return 0;
int cancel_oldtype = LIBC_CANCEL_ASYNC();
#if __HAVE_64B_ATOMICS
uint64_t d = atomic_fetch_add_relaxed (&isem->data,
(uint64_t) 1 << SEM_NWAITERS_SHIFT);
pthread_cleanup_push (__sem_wait_cleanup, isem);
for (;;)
{
if ((d & SEM_VALUE_MASK) == 0)
{
/* No token, sleep. */
if (timeout)
err = __lll_abstimed_wait_intr (
((unsigned int *) &isem->data) + SEM_VALUE_OFFSET,
0, timeout, flags, clock_id);
else
err = __lll_wait_intr (
((unsigned int *) &isem->data) + SEM_VALUE_OFFSET,
0, flags);
if (err != 0 && err != KERN_INVALID_ARGUMENT)
{
/* Error, interruption or timeout, abort. */
if (err == KERN_TIMEDOUT)
err = ETIMEDOUT;
if (err == KERN_INTERRUPTED)
err = EINTR;
ret = __hurd_fail (err);
__sem_wait_cleanup (isem);
break;
}
/* Token changed */
d = atomic_load_relaxed (&isem->data);
}
else
{
/* Try to acquire and dequeue. */
if (atomic_compare_exchange_weak_acquire (&isem->data,
&d, d - 1 - ((uint64_t) 1 << SEM_NWAITERS_SHIFT)))
{
/* Success */
ret = 0;
break;
}
}
}
pthread_cleanup_pop (0);
#else
unsigned int v;
atomic_fetch_add_acquire (&isem->nwaiters, 1);
pthread_cleanup_push (__sem_wait_cleanup, isem);
v = atomic_load_relaxed (&isem->value);
do
{
do
{
do
{
if ((v & SEM_NWAITERS_MASK) != 0)
break;
}
while (!atomic_compare_exchange_weak_release (&isem->value,
&v, v | SEM_NWAITERS_MASK));
if ((v >> SEM_VALUE_SHIFT) == 0)
{
/* No token, sleep. */
if (timeout)
err = __lll_abstimed_wait_intr (&isem->value,
SEM_NWAITERS_MASK, timeout, flags, clock_id);
else
err = __lll_wait_intr (&isem->value,
SEM_NWAITERS_MASK, flags);
if (err != 0 && err != KERN_INVALID_ARGUMENT)
{
/* Error, interruption or timeout, abort. */
if (err == KERN_TIMEDOUT)
err = ETIMEDOUT;
if (err == KERN_INTERRUPTED)
err = EINTR;
ret = __hurd_fail (err);
goto error;
}
/* Token changed */
v = atomic_load_relaxed (&isem->value);
}
}
while ((v >> SEM_VALUE_SHIFT) == 0);
}
while (!atomic_compare_exchange_weak_acquire (&isem->value,
&v, v - (1 << SEM_VALUE_SHIFT)));
error:
pthread_cleanup_pop (0);
__sem_wait_32_finish (isem);
#endif
LIBC_CANCEL_RESET (cancel_oldtype);
return ret;
}
#if !__HAVE_64B_ATOMICS
/* Stop being a registered waiter (non-64b-atomics code only). */
static void
__sem_wait_32_finish (struct new_sem *isem)
{
unsigned int wguess = atomic_load_relaxed (&isem->nwaiters);
if (wguess == 1)
atomic_fetch_and_acquire (&isem->value, ~SEM_NWAITERS_MASK);
unsigned int wfinal = atomic_fetch_add_release (&isem->nwaiters, -1);
if (wfinal > 1 && wguess == 1)
{
unsigned int v = atomic_fetch_or_relaxed (&isem->value,
SEM_NWAITERS_MASK);
v >>= SEM_VALUE_SHIFT;
while (v--)
__lll_wake (&isem->value, isem->pshared ? GSYNC_SHARED : 0);
}
}
#endif
int
__sem_clockwait (sem_t *sem, clockid_t clockid,
const struct timespec *restrict timeout)
{
return __sem_timedwait_internal (sem, clockid, timeout);
}
weak_alias (__sem_clockwait, sem_clockwait);
int
__sem_timedwait (sem_t *restrict sem, const struct timespec *restrict timeout)
{
return __sem_timedwait_internal (sem, CLOCK_REALTIME, timeout);
}
weak_alias (__sem_timedwait, sem_timedwait);
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