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/* Lock a mutex, abandoning after a certain time.
Copyright (C) 2019-2023 Free Software Foundation, Inc.
This file 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.
This file 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 this program. If not, see <https://www.gnu.org/licenses/>. */
#include <config.h>
/* Specification. */
#include <pthread.h>
#include <errno.h>
#include <limits.h>
#include <sys/time.h>
#include <time.h>
int
pthread_mutex_timedlock (pthread_mutex_t *mutex, const struct timespec *abstime)
{
/* Poll the mutex's state in regular intervals. Ugh. */
/* POSIX says:
"Under no circumstance shall the function fail with a timeout if
the mutex can be locked immediately. The validity of the abstime
parameter need not be checked if the mutex can be locked
immediately."
Therefore start the loop with a pthread_mutex_trylock call. */
for (;;)
{
int err;
struct timeval currtime;
unsigned long remaining;
err = pthread_mutex_trylock (mutex);
if (err != EBUSY)
return err;
gettimeofday (&currtime, NULL);
if (currtime.tv_sec > abstime->tv_sec)
remaining = 0;
else
{
unsigned long seconds = abstime->tv_sec - currtime.tv_sec;
remaining = seconds * 1000000000;
if (remaining / 1000000000 != seconds) /* overflow? */
remaining = ULONG_MAX;
else
{
long nanoseconds =
abstime->tv_nsec - currtime.tv_usec * 1000;
if (nanoseconds >= 0)
{
remaining += nanoseconds;
if (remaining < nanoseconds) /* overflow? */
remaining = ULONG_MAX;
}
else
{
if (remaining >= - nanoseconds)
remaining -= (- nanoseconds);
else
remaining = 0;
}
}
}
if (remaining == 0)
return ETIMEDOUT;
/* Sleep 1 ms. */
struct timespec duration = { .tv_nsec = 1000000 };
if (duration.tv_nsec > remaining)
duration.tv_nsec = remaining;
nanosleep (&duration, NULL);
}
}
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