Standardize rx_event usage

[openafs.git] / tests / rx / event-t.c

diff --git a/tests/rx/event-t.c b/tests/rx/event-t.c
index c990246..bc07fd3 100644 (file)
--- a/tests/rx/event-t.c
+++ b/tests/rx/event-t.c
@@ -44,8 +44,29 @@ eventSub(struct rxevent *event, void *arg, void *arg1, int arg2)
 {
     struct testEvent *evrecord = arg;
 
+    /*
+     * The eventListMutex protects the contents of fields in the global
+     * 'events' array, including reading/writing evrecord->event.
+     * However, in this test code, we have an additional guarantee that
+     * the events array will remain allocated for the duration of the test,
+     * and as such that it is safe to dereference |evrecord| at all.  In real
+     * application code where the passed args are pointers to allocated data
+     * structures with finite lifetime, the programmer must ensure that the
+     * firing event can safely access these fields (i.e., that the object
+     * lifetime does not permit the object to be destroyed while an event
+     * pointing to it is outstanding or in progress).  The simplest way to
+     * do this (for reference counted objects) is to have the pending event
+     * hold a reference on the pointed-to object. This reference should be
+     * dropped at the end of the event handler or if the event is
+     * (successfully!) cancelled before it fires.  Other strategies are also
+     * possible, such as deferring object destruction until after all pending
+     * events have run or gotten cancelled, noting that the calling code must
+     * take care to allow the event handler to obtain any needed locks and
+     * avoid deadlock.
+     */
     pthread_mutex_lock(&eventListMutex);
-    rxevent_Put(&evrecord->event);
+    if (evrecord->event != NULL)
+       rxevent_Put(&evrecord->event);
     evrecord->event = NULL;
     evrecord->fired = 1;
     pthread_mutex_unlock(&eventListMutex);
@@ -116,8 +137,7 @@ main(void)
     /* Test for a problem when there is only a single event in the tree */
     event = rxevent_Post(&now, &now, reportSub, NULL, NULL, 0);
     ok(event != NULL, "Created a single event");
-    rxevent_Cancel(&event);
-    ok(1, "Cancelled a single event");
+    ok(rxevent_Cancel(&event), "Cancelled a single event");
     rxevent_RaiseEvents(&now);
     ok(1, "RaiseEvents happened without error");
 
@@ -151,10 +171,8 @@ main(void)
        if (random() % 4 == 0) {
            int victim = random() % counter;
 
-           if (events[victim].event != NULL) {
-               rxevent_Cancel(&events[victim].event);
+           if (rxevent_Cancel(&events[victim].event))
                events[victim].cancelled = 1;
-           }
        }
        pthread_mutex_unlock(&eventListMutex);
     }