71 lines
1.9 KiB
C
71 lines
1.9 KiB
C
/*
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* Copyright (c) 2014 Jonas 'Sortie' Termansen.
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*
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* Permission to use, copy, modify, and distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*
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* semaphore/sem_timedwait.c
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* Lock a semaphore.
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*/
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#include <errno.h>
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#include <sched.h>
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#include <semaphore.h>
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#include <signal.h>
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#include <stddef.h>
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#include <time.h>
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#include <timespec.h>
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int sem_timedwait(sem_t* restrict sem, const struct timespec* restrict abstime)
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{
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if ( sem_trywait(sem) == 0 )
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return 0;
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if ( errno != EAGAIN )
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return -1;
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sigset_t old_set_mask;
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sigset_t old_set_allowed;
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sigset_t all_signals;
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sigfillset(&all_signals);
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sigprocmask(SIG_SETMASK, &all_signals, &old_set_mask);
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signotset(&old_set_allowed, &old_set_mask);
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while ( sem_trywait(sem) != 0 )
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{
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// TODO: Using CLOCK_REALTIME for this is bad as it is not monotonic. We
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// need to enchance the semaphore API so a better clock can be
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// used instead.
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if ( errno == EAGAIN )
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{
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struct timespec now;
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clock_gettime(CLOCK_REALTIME, &now);
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if ( timespec_le(*abstime, now) )
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errno = ETIMEDOUT;
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}
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if ( errno == EAGAIN && sigpending(&old_set_allowed) )
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errno = EINTR;
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if ( errno != EAGAIN )
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{
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sigprocmask(SIG_SETMASK, &old_set_mask, NULL);
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return -1;
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}
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sched_yield();
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}
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sigprocmask(SIG_SETMASK, &old_set_mask, NULL);
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return 0;
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}
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