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-rw-r--r--linuxthreads/condvar.c324
1 files changed, 278 insertions, 46 deletions
diff --git a/linuxthreads/condvar.c b/linuxthreads/condvar.c
index 2ea7513c68..87a93a9115 100644
--- a/linuxthreads/condvar.c
+++ b/linuxthreads/condvar.c
@@ -25,6 +25,22 @@
#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)
{
@@ -39,54 +55,125 @@ int pthread_cond_destroy(pthread_cond_t *cond)
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);
- enqueue(&cond->__c_waiting, 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_with_cancellation(self);
- pthread_mutex_lock(mutex);
- /* This is a cancellation point */
- if (THREAD_GETMEM(self, p_canceled)
+
+ 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) {
- /* Remove ourselves from the waiting queue if we're still on it */
- __pthread_lock(&cond->__c_lock, self);
- remove_from_queue(&cond->__c_waiting, self);
- __pthread_unlock(&cond->__c_lock);
+ 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(pthread_cond_t *cond,
+pthread_cond_timedwait_relative_old(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;
+ int retsleep, already_canceled, was_signalled;
sigjmp_buf jmpbuf;
+ pthread_extricate_if extr;
+
+requeue_and_wait_again:
- /* Wait on the condition */
+ retsleep = 0;
+ already_canceled = 0;
+ was_signalled = 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);
+
+ /* Enqueue to wait on the condition and check for cancellation. */
__pthread_lock(&cond->__c_lock, self);
- enqueue(&cond->__c_waiting, 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);
- continue_waiting:
- /* Set up a longjmp handler for the restart and cancel signals */
- if (sigsetjmp(jmpbuf, 1) == 0) {
- THREAD_SETMEM(self, p_signal_jmp, &jmpbuf);
- THREAD_SETMEM(self, p_cancel_jmp, &jmpbuf);
- THREAD_SETMEM(self, p_signal, 0);
- /* Check for cancellation */
- if (THREAD_GETMEM(self, p_canceled)
- && THREAD_GETMEM(self, p_cancelstate) == PTHREAD_CANCEL_ENABLE) {
- retsleep = -1;
- } else {
+
+ 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);
@@ -95,37 +182,180 @@ pthread_cond_timedwait_relative(pthread_cond_t *cond,
retsleep = __libc_nanosleep(reltime, NULL);
/* Block the restart signal again */
sigprocmask(SIG_SETMASK, &initial_mask, NULL);
+ was_signalled = 0;
+ } else {
+ retsleep = -1;
+ was_signalled = 1;
}
- } else {
- retsleep = -1;
+ THREAD_SETMEM(self, p_signal_jmp, NULL);
}
- THREAD_SETMEM(self, p_signal_jmp, NULL);
- THREAD_SETMEM(self, p_cancel_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) */
- /* This is a cancellation point */
- if (THREAD_GETMEM(self, p_canceled)
+
+ /* 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);
+
+ if (retsleep == 0)
+ return ETIMEDOUT;
+ /* Woken by a signal: resume waiting as
+ required by Single Unix Specification. */
+ goto requeue_and_wait_again;
+ }
+
+ 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) {
- __pthread_lock(&cond->__c_lock, self);
- remove_from_queue(&cond->__c_waiting, self);
- __pthread_unlock(&cond->__c_lock);
+ THREAD_SETMEM(self, p_woken_by_cancel, 0);
pthread_mutex_lock(mutex);
pthread_exit(PTHREAD_CANCELED);
}
- /* If not signaled: also remove ourselves and return an error code, but
- only if the timeout has elapsed. If not, just continue waiting. */
- if (THREAD_GETMEM(self, p_signal) == 0) {
- if (retsleep != 0)
- goto continue_waiting;
+
+ 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 * reltime)
+{
+ volatile pthread_descr self = thread_self();
+ sigset_t unblock, initial_mask;
+ int retsleep, already_canceled, was_signalled;
+ sigjmp_buf jmpbuf;
+ pthread_extricate_if extr;
+
+ requeue_and_wait_again:
+
+ retsleep = 0;
+ already_canceled = 0;
+ was_signalled = 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);
+
+ /* 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);
+ /* Sleep for the required duration */
+ retsleep = __libc_nanosleep(reltime, NULL);
+ /* Block the restart signal again */
+ sigprocmask(SIG_SETMASK, &initial_mask, NULL);
+ was_signalled = 0;
+ } else {
+ retsleep = -1;
+ 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);
- remove_from_queue(&cond->__c_waiting, 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);
+
+ if (retsleep == 0)
+ return ETIMEDOUT;
+ /* Woken by a signal: resume waiting as
+ required by Single Unix Specification. */
+ goto requeue_and_wait_again;
+ }
+
+ /* 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);
- return ETIMEDOUT;
+ pthread_exit(PTHREAD_CANCELED);
}
- /* Otherwise, return normally */
+
pthread_mutex_lock(mutex);
return 0;
}
@@ -144,7 +374,9 @@ int pthread_cond_timedwait(pthread_cond_t *cond, pthread_mutex_t *mutex,
reltime.tv_sec -= 1;
}
if (reltime.tv_sec < 0) return ETIMEDOUT;
- return pthread_cond_timedwait_relative(cond, mutex, &reltime);
+
+ /* Indirect call through pointer! */
+ return pthread_cond_tw_rel(cond, mutex, &reltime);
}
int pthread_cond_signal(pthread_cond_t *cond)
generated by cgit v1.2.3 (git 2.25.1) at 2024-07-12 20:50:18 +0000