diff options
Diffstat (limited to 'linuxthreads/condvar.c')
| -rw-r--r-- | linuxthreads/condvar.c | 207 |
1 files changed, 207 insertions, 0 deletions
diff --git a/linuxthreads/condvar.c b/linuxthreads/condvar.c new file mode 100644 index 0000000000..6807522edc --- /dev/null +++ b/linuxthreads/condvar.c @@ -0,0 +1,207 @@ +/* Linuxthreads - a simple clone()-based implementation of Posix */ +/* threads for Linux. */ +/* Copyright (C) 1996 Xavier Leroy (Xavier.Leroy@inria.fr) */ +/* and Pavel Krauz (krauz@fsid.cvut.cz). */ +/* */ +/* This program is free software; you can redistribute it and/or */ +/* modify it under the terms of the GNU Library General Public License */ +/* as published by the Free Software Foundation; either version 2 */ +/* of the License, or (at your option) any later version. */ +/* */ +/* This program 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 Library General Public License for more details. */ + +/* Condition variables */ + +#include <errno.h> +#include <sched.h> +#include <stddef.h> +#include <sys/time.h> +#include "pthread.h" +#include "internals.h" +#include "spinlock.h" +#include "queue.h" +#include "restart.h" + +static void remove_from_queue(pthread_queue * q, pthread_descr th); + +int pthread_cond_init(pthread_cond_t *cond, + const pthread_condattr_t *cond_attr) +{ + cond->c_spinlock = 0; + queue_init(&cond->c_waiting); + return 0; +} + +int pthread_cond_destroy(pthread_cond_t *cond) +{ + pthread_descr head; + + acquire(&cond->c_spinlock); + head = cond->c_waiting.head; + release(&cond->c_spinlock); + if (head != NULL) return EBUSY; + return 0; +} + +int pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex) +{ + volatile pthread_descr self = thread_self(); + acquire(&cond->c_spinlock); + enqueue(&cond->c_waiting, self); + release(&cond->c_spinlock); + pthread_mutex_unlock(mutex); + suspend_with_cancellation(self); + pthread_mutex_lock(mutex); + /* This is a cancellation point */ + if (self->p_canceled && self->p_cancelstate == PTHREAD_CANCEL_ENABLE) { + /* Remove ourselves from the waiting queue if we're still on it */ + acquire(&cond->c_spinlock); + remove_from_queue(&cond->c_waiting, self); + release(&cond->c_spinlock); + pthread_exit(PTHREAD_CANCELED); + } + return 0; +} + +static inline int +pthread_cond_timedwait_relative(pthread_cond_t *cond, + pthread_mutex_t *mutex, + const struct timespec * reltime) +{ + volatile pthread_descr self = thread_self(); + sigset_t unblock, initial_mask; + int retsleep; + sigjmp_buf jmpbuf; + + /* Wait on the condition */ + acquire(&cond->c_spinlock); + enqueue(&cond->c_waiting, self); + release(&cond->c_spinlock); + pthread_mutex_unlock(mutex); + /* Set up a longjmp handler for the restart signal */ + /* No need to save the signal mask, since PTHREAD_SIG_RESTART will be + blocked when doing the siglongjmp, and we'll just leave it blocked. */ + if (sigsetjmp(jmpbuf, 0) == 0) { + self->p_signal_jmp = &jmpbuf; + self->p_signal = 0; + /* Check for cancellation */ + if (self->p_canceled && self->p_cancelstate == PTHREAD_CANCEL_ENABLE) { + retsleep = -1; + } else { + /* Unblock the restart signal */ + sigemptyset(&unblock); + sigaddset(&unblock, PTHREAD_SIG_RESTART); + sigprocmask(SIG_UNBLOCK, &unblock, &initial_mask); + /* Sleep for the required duration */ + retsleep = __libc_nanosleep(reltime, NULL); + /* Block the restart signal again */ + sigprocmask(SIG_SETMASK, &initial_mask, NULL); + } + } else { + retsleep = -1; + } + self->p_signal_jmp = NULL; + /* Here, either the condition was signaled (self->p_signal != 0) + or we got canceled (self->p_canceled != 0) + or the timeout occurred (retsleep == 0) + or another interrupt occurred (retsleep == -1) */ + /* Re-acquire the spinlock */ + acquire(&cond->c_spinlock); + /* This is a cancellation point */ + if (self->p_canceled && self->p_cancelstate == PTHREAD_CANCEL_ENABLE) { + remove_from_queue(&cond->c_waiting, self); + release(&cond->c_spinlock); + pthread_mutex_lock(mutex); + pthread_exit(PTHREAD_CANCELED); + } + /* If not signaled: also remove ourselves and return an error code */ + if (self->p_signal == 0) { + remove_from_queue(&cond->c_waiting, self); + release(&cond->c_spinlock); + pthread_mutex_lock(mutex); + return retsleep == 0 ? ETIMEDOUT : EINTR; + } + /* Otherwise, return normally */ + release(&cond->c_spinlock); + pthread_mutex_lock(mutex); + return 0; +} + +int pthread_cond_timedwait(pthread_cond_t *cond, pthread_mutex_t *mutex, + const struct timespec * abstime) +{ + struct timeval now; + struct timespec reltime; + /* Compute a time offset relative to now */ + __gettimeofday(&now, NULL); + reltime.tv_sec = abstime->tv_sec - now.tv_sec; + reltime.tv_nsec = abstime->tv_nsec - now.tv_usec * 1000; + if (reltime.tv_nsec < 0) { + reltime.tv_nsec += 1000000000; + reltime.tv_sec -= 1; + } + if (reltime.tv_sec < 0) return ETIMEDOUT; + return pthread_cond_timedwait_relative(cond, mutex, &reltime); +} + +int pthread_cond_signal(pthread_cond_t *cond) +{ + pthread_descr th; + + acquire(&cond->c_spinlock); + th = dequeue(&cond->c_waiting); + release(&cond->c_spinlock); + if (th != NULL) restart(th); + return 0; +} + +int pthread_cond_broadcast(pthread_cond_t *cond) +{ + pthread_queue tosignal; + pthread_descr th; + + acquire(&cond->c_spinlock); + /* Copy the current state of the waiting queue and empty it */ + tosignal = cond->c_waiting; + queue_init(&cond->c_waiting); + release(&cond->c_spinlock); + /* Now signal each process in the queue */ + while ((th = dequeue(&tosignal)) != NULL) restart(th); + return 0; +} + +int pthread_condattr_init(pthread_condattr_t *attr) +{ + return 0; +} + +int pthread_condattr_destroy(pthread_condattr_t *attr) +{ + return 0; +} + +/* Auxiliary function on queues */ + +static void remove_from_queue(pthread_queue * q, pthread_descr th) +{ + pthread_descr t; + + if (q->head == NULL) return; + if (q->head == th) { + q->head = th->p_nextwaiting; + if (q->head == NULL) q->tail = NULL; + th->p_nextwaiting = NULL; + return; + } + for (t = q->head; t->p_nextwaiting != NULL; t = t->p_nextwaiting) { + if (t->p_nextwaiting == th) { + t->p_nextwaiting = th->p_nextwaiting; + if (th->p_nextwaiting == NULL) q->tail = t; + th->p_nextwaiting = NULL; + return; + } + } +} |