Redesigned how cancellation unblocks a thread from internal cancellation points (sem_wait, pthread_join, pthread_cond_{wait,timedwait}). Cancellation won't eat a signal in any of these functions (*required* by POSIX and Single Unix Spec!).

2000-01-03  Kaz Kylheku  <kaz@ashi.footprints.net>

	Redesigned how cancellation unblocks a thread from internal
	cancellation points (sem_wait, pthread_join,
	pthread_cond_{wait,timedwait}).
	Cancellation won't eat a signal in any of these functions
	(*required* by POSIX and Single Unix Spec!).
	* condvar.c: spontaneous wakeup on pthread_cond_timedwait won't eat a
	simultaneous condition variable signal (not required by POSIX
	or Single Unix Spec, but nice).
	* spinlock.c: __pthread_lock queues back any received restarts
	that don't belong to it instead of assuming ownership of lock
	upon any restart; fastlock can no longer be acquired by two threads
	simultaneously.
	* restart.h: restarts queue even on kernels that don't have
	queued real time signals (2.0, early 2.1), thanks to atomic counter,
	avoiding a rare race condition in pthread_cond_timedwait.

1 files changed, 22 insertions, 2 deletions

diff --git a/linuxthreads/oldsemaphore.c b/linuxthreads/oldsemaphore.c
index 72d12d2..62d2812 100644
--- a/linuxthreads/oldsemaphore.c
+++ b/linuxthreads/oldsemaphore.c
@@ -68,13 +68,29 @@ int __old_sem_init(old_sem_t *sem, int pshared, unsigned int value)
   return 0;
 }
 
+/* Function called by pthread_cancel to remove the thread from
+   waiting inside __old_sem_wait. Here we simply unconditionally
+   indicate that the thread is to be woken, by returning 1. */
+
+static int old_sem_extricate_func(void *obj, pthread_descr th)
+{
+    return 1;
+}
+
 int __old_sem_wait(old_sem_t * sem)
 {
     long oldstatus, newstatus;
     volatile pthread_descr self = thread_self();
     pthread_descr * th;
+    pthread_extricate_if extr;
+
+    /* Set up extrication interface */
+    extr.pu_object = 0;
+    extr.pu_extricate_func = old_sem_extricate_func;
 
     while (1) {
+	/* Register extrication interface */
+	__pthread_set_own_extricate_if(self, &extr); 
 	do {
             oldstatus = sem->sem_status;
             if ((oldstatus & 1) && (oldstatus != 1))
@@ -85,11 +101,15 @@ int __old_sem_wait(old_sem_t * sem)
 	    }
 	}
 	while (! sem_compare_and_swap(sem, oldstatus, newstatus));
-	if (newstatus & 1)
+	if (newstatus & 1) {
 	    /* We got the semaphore. */
+	  __pthread_set_own_extricate_if(self, 0); 
 	    return 0;
+	}
 	/* Wait for sem_post or cancellation */
-	suspend_with_cancellation(self);
+	suspend(self);
+	__pthread_set_own_extricate_if(self, 0); 
+
 	/* This is a cancellation point */
 	if (self->p_canceled && self->p_cancelstate == PTHREAD_CANCEL_ENABLE) {
 	    /* Remove ourselves from the waiting list if we're still on it */