diff options
Diffstat (limited to 'libpthread/linuxthreads/condvar.c')
| -rw-r--r-- | libpthread/linuxthreads/condvar.c | 417 |
1 files changed, 417 insertions, 0 deletions
diff --git a/libpthread/linuxthreads/condvar.c b/libpthread/linuxthreads/condvar.c new file mode 100644 index 000000000..85754a18f --- /dev/null +++ b/libpthread/linuxthreads/condvar.c @@ -0,0 +1,417 @@ +/* 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 int pthread_cond_timedwait_relative_old(pthread_cond_t *, + pthread_mutex_t *, const struct timespec *); + +static int pthread_cond_timedwait_relative_new(pthread_cond_t *, + pthread_mutex_t *, const struct timespec *); + +static int (*pthread_cond_tw_rel)(pthread_cond_t *, pthread_mutex_t *, + const struct timespec *) = pthread_cond_timedwait_relative_old; + +/* initialize this module */ +void __pthread_init_condvar(int rt_sig_available) +{ + if (rt_sig_available) + pthread_cond_tw_rel = pthread_cond_timedwait_relative_new; +} + +int pthread_cond_init(pthread_cond_t *cond, + const pthread_condattr_t *cond_attr) +{ + __pthread_init_lock(&cond->__c_lock); + cond->__c_waiting = NULL; + return 0; +} + +int pthread_cond_destroy(pthread_cond_t *cond) +{ + if (cond->__c_waiting != NULL) return EBUSY; + return 0; +} + +/* Function called by pthread_cancel to remove the thread from + waiting on a condition variable queue. */ + +static int cond_extricate_func(void *obj, pthread_descr th) +{ + volatile pthread_descr self = thread_self(); + pthread_cond_t *cond = obj; + int did_remove = 0; + + __pthread_lock(&cond->__c_lock, self); + did_remove = remove_from_queue(&cond->__c_waiting, th); + __pthread_unlock(&cond->__c_lock); + + return did_remove; +} + +int pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex) +{ + volatile pthread_descr self = thread_self(); + pthread_extricate_if extr; + int already_canceled = 0; + + /* Set up extrication interface */ + extr.pu_object = cond; + extr.pu_extricate_func = cond_extricate_func; + + /* Register extrication interface */ + __pthread_set_own_extricate_if(self, &extr); + + /* Atomically enqueue thread for waiting, but only if it is not + canceled. If the thread is canceled, then it will fall through the + suspend call below, and then call pthread_exit without + having to worry about whether it is still on the condition variable queue. + This depends on pthread_cancel setting p_canceled before calling the + extricate function. */ + + __pthread_lock(&cond->__c_lock, self); + if (!(THREAD_GETMEM(self, p_canceled) + && THREAD_GETMEM(self, p_cancelstate) == PTHREAD_CANCEL_ENABLE)) + enqueue(&cond->__c_waiting, self); + else + already_canceled = 1; + __pthread_unlock(&cond->__c_lock); + + if (already_canceled) { + __pthread_set_own_extricate_if(self, 0); + pthread_exit(PTHREAD_CANCELED); + } + + pthread_mutex_unlock(mutex); + + suspend(self); + __pthread_set_own_extricate_if(self, 0); + + /* Check for cancellation again, to provide correct cancellation + point behavior */ + + if (THREAD_GETMEM(self, p_woken_by_cancel) + && THREAD_GETMEM(self, p_cancelstate) == PTHREAD_CANCEL_ENABLE) { + THREAD_SETMEM(self, p_woken_by_cancel, 0); + pthread_mutex_lock(mutex); + pthread_exit(PTHREAD_CANCELED); + } + + pthread_mutex_lock(mutex); + return 0; +} + +/* The following function is used on kernels that don't have rt signals. + SIGUSR1 is used as the restart signal. The different code is needed + because that ordinary signal does not queue. */ + +static int +pthread_cond_timedwait_relative_old(pthread_cond_t *cond, + pthread_mutex_t *mutex, + const struct timespec * abstime) +{ + volatile pthread_descr self = thread_self(); + sigset_t unblock, initial_mask; + int already_canceled = 0; + int was_signalled = 0; + sigjmp_buf jmpbuf; + pthread_extricate_if extr; + + /* Set up extrication interface */ + extr.pu_object = cond; + extr.pu_extricate_func = cond_extricate_func; + + /* Register extrication interface */ + __pthread_set_own_extricate_if(self, &extr); + + /* Enqueue to wait on the condition and check for cancellation. */ + __pthread_lock(&cond->__c_lock, self); + if (!(THREAD_GETMEM(self, p_canceled) + && THREAD_GETMEM(self, p_cancelstate) == PTHREAD_CANCEL_ENABLE)) + enqueue(&cond->__c_waiting, self); + else + already_canceled = 1; + __pthread_unlock(&cond->__c_lock); + + if (already_canceled) { + __pthread_set_own_extricate_if(self, 0); + pthread_exit(PTHREAD_CANCELED); + } + + pthread_mutex_unlock(mutex); + + if (atomic_decrement(&self->p_resume_count) == 0) { + /* Set up a longjmp handler for the restart signal, unblock + the signal and sleep. */ + + if (sigsetjmp(jmpbuf, 1) == 0) { + THREAD_SETMEM(self, p_signal_jmp, &jmpbuf); + THREAD_SETMEM(self, p_signal, 0); + /* Unblock the restart signal */ + sigemptyset(&unblock); + sigaddset(&unblock, __pthread_sig_restart); + sigprocmask(SIG_UNBLOCK, &unblock, &initial_mask); + + while (1) { + struct timeval now; + struct timespec reltime; + + /* Compute a time offset relative to now. */ + gettimeofday (&now, NULL); + reltime.tv_nsec = abstime->tv_nsec - now.tv_usec * 1000; + reltime.tv_sec = abstime->tv_sec - now.tv_sec; + if (reltime.tv_nsec < 0) { + reltime.tv_nsec += 1000000000; + reltime.tv_sec -= 1; + } + + /* Sleep for the required duration. If woken by a signal, resume waiting + as required by Single Unix Specification. */ + if (reltime.tv_sec < 0 || __libc_nanosleep(&reltime, NULL) == 0) + break; + } + + /* Block the restart signal again */ + sigprocmask(SIG_SETMASK, &initial_mask, NULL); + was_signalled = 0; + } else { + was_signalled = 1; + } + THREAD_SETMEM(self, p_signal_jmp, NULL); + } + + /* Now was_signalled is true if we exited the above code + due to the delivery of a restart signal. In that case, + we know we have been dequeued and resumed and that the + resume count is balanced. Otherwise, there are some + cases to consider. First, try to bump up the resume count + back to zero. If it goes to 1, it means restart() was + invoked on this thread. The signal must be consumed + and the count bumped down and everything is cool. + Otherwise, no restart was delivered yet, so we remove + the thread from the queue. If this succeeds, it's a clear + case of timeout. If we fail to remove from the queue, then we + must wait for a restart. */ + + if (!was_signalled) { + if (atomic_increment(&self->p_resume_count) != -1) { + __pthread_wait_for_restart_signal(self); + atomic_decrement(&self->p_resume_count); /* should be zero now! */ + } else { + int was_on_queue; + __pthread_lock(&cond->__c_lock, self); + was_on_queue = remove_from_queue(&cond->__c_waiting, self); + __pthread_unlock(&cond->__c_lock); + + if (was_on_queue) { + __pthread_set_own_extricate_if(self, 0); + pthread_mutex_lock(mutex); + return ETIMEDOUT; + } + + suspend(self); + } + } + + __pthread_set_own_extricate_if(self, 0); + + /* The remaining logic is the same as in other cancellable waits, + such as pthread_join sem_wait or pthread_cond wait. */ + + if (THREAD_GETMEM(self, p_woken_by_cancel) + && THREAD_GETMEM(self, p_cancelstate) == PTHREAD_CANCEL_ENABLE) { + THREAD_SETMEM(self, p_woken_by_cancel, 0); + pthread_mutex_lock(mutex); + pthread_exit(PTHREAD_CANCELED); + } + + pthread_mutex_lock(mutex); + return 0; +} + +/* The following function is used on new (late 2.1 and 2.2 and higher) kernels + that have rt signals which queue. */ + +static int +pthread_cond_timedwait_relative_new(pthread_cond_t *cond, + pthread_mutex_t *mutex, + const struct timespec * abstime) +{ + volatile pthread_descr self = thread_self(); + sigset_t unblock, initial_mask; + int already_canceled = 0; + int was_signalled = 0; + sigjmp_buf jmpbuf; + pthread_extricate_if extr; + + /* Set up extrication interface */ + extr.pu_object = cond; + extr.pu_extricate_func = cond_extricate_func; + + /* Register extrication interface */ + __pthread_set_own_extricate_if(self, &extr); + + /* Enqueue to wait on the condition and check for cancellation. */ + __pthread_lock(&cond->__c_lock, self); + if (!(THREAD_GETMEM(self, p_canceled) + && THREAD_GETMEM(self, p_cancelstate) == PTHREAD_CANCEL_ENABLE)) + enqueue(&cond->__c_waiting, self); + else + already_canceled = 1; + __pthread_unlock(&cond->__c_lock); + + if (already_canceled) { + __pthread_set_own_extricate_if(self, 0); + pthread_exit(PTHREAD_CANCELED); + } + + pthread_mutex_unlock(mutex); + + /* Set up a longjmp handler for the restart signal, unblock + the signal and sleep. */ + + if (sigsetjmp(jmpbuf, 1) == 0) { + THREAD_SETMEM(self, p_signal_jmp, &jmpbuf); + THREAD_SETMEM(self, p_signal, 0); + /* Unblock the restart signal */ + sigemptyset(&unblock); + sigaddset(&unblock, __pthread_sig_restart); + sigprocmask(SIG_UNBLOCK, &unblock, &initial_mask); + + while (1) { + struct timeval now; + struct timespec reltime; + + /* Compute a time offset relative to now. */ + gettimeofday (&now, NULL); + reltime.tv_nsec = abstime->tv_nsec - now.tv_usec * 1000; + reltime.tv_sec = abstime->tv_sec - now.tv_sec; + if (reltime.tv_nsec < 0) { + reltime.tv_nsec += 1000000000; + reltime.tv_sec -= 1; + } + + /* Sleep for the required duration. If woken by a signal, + resume waiting as required by Single Unix Specification. */ + if (reltime.tv_sec < 0 || __libc_nanosleep(&reltime, NULL) == 0) + break; + } + + /* Block the restart signal again */ + sigprocmask(SIG_SETMASK, &initial_mask, NULL); + was_signalled = 0; + } else { + was_signalled = 1; + } + THREAD_SETMEM(self, p_signal_jmp, NULL); + + /* Now was_signalled is true if we exited the above code + due to the delivery of a restart signal. In that case, + everything is cool. We have been removed from the queue + by the other thread, and consumed its signal. + + Otherwise we this thread woke up spontaneously, or due to a signal other + than restart. The next thing to do is to try to remove the thread + from the queue. This may fail due to a race against another thread + trying to do the same. In the failed case, we know we were signalled, + and we may also have to consume a restart signal. */ + + if (!was_signalled) { + int was_on_queue; + + /* __pthread_lock will queue back any spurious restarts that + may happen to it. */ + + __pthread_lock(&cond->__c_lock, self); + was_on_queue = remove_from_queue(&cond->__c_waiting, self); + __pthread_unlock(&cond->__c_lock); + + if (was_on_queue) { + __pthread_set_own_extricate_if(self, 0); + pthread_mutex_lock(mutex); + return ETIMEDOUT; + } + + /* Eat the outstanding restart() from the signaller */ + suspend(self); + } + + __pthread_set_own_extricate_if(self, 0); + + /* The remaining logic is the same as in other cancellable waits, + such as pthread_join sem_wait or pthread_cond wait. */ + + if (THREAD_GETMEM(self, p_woken_by_cancel) + && THREAD_GETMEM(self, p_cancelstate) == PTHREAD_CANCEL_ENABLE) { + THREAD_SETMEM(self, p_woken_by_cancel, 0); + pthread_mutex_lock(mutex); + pthread_exit(PTHREAD_CANCELED); + } + + pthread_mutex_lock(mutex); + return 0; +} + +int pthread_cond_timedwait(pthread_cond_t *cond, pthread_mutex_t *mutex, + const struct timespec * abstime) +{ + /* Indirect call through pointer! */ + return pthread_cond_tw_rel(cond, mutex, abstime); +} + +int pthread_cond_signal(pthread_cond_t *cond) +{ + pthread_descr th; + + __pthread_lock(&cond->__c_lock, NULL); + th = dequeue(&cond->__c_waiting); + __pthread_unlock(&cond->__c_lock); + if (th != NULL) restart(th); + return 0; +} + +int pthread_cond_broadcast(pthread_cond_t *cond) +{ + pthread_descr tosignal, th; + + __pthread_lock(&cond->__c_lock, NULL); + /* Copy the current state of the waiting queue and empty it */ + tosignal = cond->__c_waiting; + cond->__c_waiting = NULL; + __pthread_unlock(&cond->__c_lock); + /* 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; +} |