sched: ast_sched_del may return prematurely due to spurious wakeup
authorJoshua Colp <jcolp@digium.com>
Sat, 29 Aug 2015 00:57:14 +0000 (21:57 -0300)
committerJoshua Colp <jcolp@digium.com>
Sat, 29 Aug 2015 01:04:53 +0000 (20:04 -0500)
When deleting a scheduled item if the item in question is currently
executing the ast_sched_del function waits until it has completed.
This is accomplished using ast_cond_wait. Unfortunately the
ast_cond_wait function can suffer from spurious wakeups so the
predicate needs to be checked after it returns to make sure it has
really woken up as a result of being signaled.

This change adds a loop around the ast_cond_wait to make sure that
it only exits when the executing task has really completed.

ASTERISK-25355 #close

Change-Id: I51198270eb0b637c956c61aa409f46283432be61

main/sched.c

index d50a31e..062b2fd 100644 (file)
@@ -497,7 +497,9 @@ int _ast_sched_del(struct ast_sched_context *con, int id, const char *file, int
                /* Wait for executing task to complete so that caller of ast_sched_del() does not
                 * free memory out from under the task.
                 */
-               ast_cond_wait(&s->cond, &con->lock);
+               while (con->currently_executing && (id == con->currently_executing->id)) {
+                       ast_cond_wait(&s->cond, &con->lock);
+               }
                /* Do not sched_release() here because ast_sched_runq() will do it */
        }