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sortix--sortix/libpthread/sem_timedwait.c++
Jonas 'Sortie' Termansen 392472af5c Add semaphores API.
2014-11-30 19:31:40 +01:00

76 lines
2.1 KiB
C++

/*******************************************************************************
Copyright(C) Jonas 'Sortie' Termansen 2014.
This file is part of Sortix libpthread.
Sortix libpthread 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 3 of the License, or (at your
option) any later version.
Sortix libpthread 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 Sortix libpthread. If not, see <http://www.gnu.org/licenses/>.
sem_timedwait.c++
Lock a semaphore.
*******************************************************************************/
#include <errno.h>
#include <sched.h>
#include <semaphore.h>
#include <signal.h>
#include <stddef.h>
#include <time.h>
#include <timespec.h>
extern "C"
int sem_timedwait(sem_t* restrict sem, const struct timespec* restrict abstime)
{
if ( sem_trywait(sem) == 0 )
return 0;
if ( errno != EAGAIN )
return -1;
sigset_t old_set_mask;
sigset_t old_set_allowed;
sigset_t all_signals;
sigfillset(&all_signals);
sigprocmask(SIG_SETMASK, &all_signals, &old_set_mask);
signotset(&old_set_allowed, &old_set_mask);
while ( sem_trywait(sem) != 0 )
{
// TODO: Using CLOCK_REALTIME for this is bad as it is not monotonic. We
// need to enchance the semaphore API so a better clock can be
// used instead.
if ( errno == EAGAIN )
{
struct timespec now;
clock_gettime(CLOCK_REALTIME, &now);
if ( timespec_le(*abstime, now) )
errno = ETIMEDOUT;
}
if ( errno == EAGAIN && sigpending(&old_set_allowed) )
errno = EINTR;
if ( errno != EAGAIN )
{
sigprocmask(SIG_SETMASK, &old_set_mask, NULL);
return -1;
}
sched_yield();
}
sigprocmask(SIG_SETMASK, &old_set_mask, NULL);
return 0;
}