88 lines
2.7 KiB
C
88 lines
2.7 KiB
C
/* Lock a mutex, abandoning after a certain time.
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Copyright (C) 2019-2020 Free Software Foundation, Inc.
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program 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
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <https://www.gnu.org/licenses/>. */
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#include <config.h>
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/* Specification. */
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#include <pthread.h>
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#include <errno.h>
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#include <limits.h>
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#include <sys/time.h>
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#include <time.h>
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int
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pthread_mutex_timedlock (pthread_mutex_t *mutex, const struct timespec *abstime)
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{
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/* Poll the mutex's state in regular intervals. Ugh. */
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/* POSIX says:
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"Under no circumstance shall the function fail with a timeout if
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the mutex can be locked immediately. The validity of the abstime
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parameter need not be checked if the mutex can be locked
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immediately."
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Therefore start the loop with a pthread_mutex_trylock call. */
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for (;;)
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{
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int err;
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struct timeval currtime;
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unsigned long remaining;
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struct timespec duration;
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err = pthread_mutex_trylock (mutex);
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if (err != EBUSY)
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return err;
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gettimeofday (&currtime, NULL);
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if (currtime.tv_sec > abstime->tv_sec)
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remaining = 0;
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else
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{
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unsigned long seconds = abstime->tv_sec - currtime.tv_sec;
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remaining = seconds * 1000000000;
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if (remaining / 1000000000 != seconds) /* overflow? */
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remaining = ULONG_MAX;
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else
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{
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long nanoseconds =
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abstime->tv_nsec - currtime.tv_usec * 1000;
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if (nanoseconds >= 0)
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{
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remaining += nanoseconds;
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if (remaining < nanoseconds) /* overflow? */
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remaining = ULONG_MAX;
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}
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else
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{
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if (remaining >= - nanoseconds)
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remaining -= (- nanoseconds);
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else
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remaining = 0;
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}
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}
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}
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if (remaining == 0)
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return ETIMEDOUT;
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/* Sleep 1 ms. */
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duration.tv_sec = 0;
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duration.tv_nsec = 1000000;
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if (duration.tv_nsec > remaining)
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duration.tv_nsec = remaining;
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nanosleep (&duration, NULL);
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}
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}
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