posix timers using == instead of & for bitmask tests

Make posix-timers do a get_task_struct / put_task_struct if either SIGEV_SIGNAL or SIGEV_THREAD_ID is set. Currently the get/put is done only if both are set.

Compiles but is otherwise untested.

Joe

@@ -548,7 +548,7 @@
 	}
 	sigqueue_free(tmr->sigq);
 	if (unlikely(tmr->it_process) &&
-	    tmr->it_sigev_notify == (SIGEV_SIGNAL|SIGEV_THREAD_ID))
+	    (tmr->it_sigev_notify & (SIGEV_SIGNAL | SIGEV_THREAD_ID)))
 		put_task_struct(tmr->it_process);
 	kmem_cache_free(posix_timers_cache, tmr);
 }

@@ -650,7 +650,7 @@
 				list_add(&new_timer->list,
 					 &process->signal->posix_timers);
 				spin_unlock_irqrestore(&process->sighand->siglock, flags);
-				if (new_timer->it_sigev_notify == (SIGEV_SIGNAL|SIGEV_THREAD_ID))
+				if (new_timer->it_sigev_notify & (SIGEV_SIGNAL | SIGEV_THREAD_ID))
 					get_task_struct(process);
 			} else {
 				spin_unlock_irqrestore(&process->sighand->siglock, flags);

@@ -1101,7 +1101,7 @@
 	 * they got something (see the lock code above).
 	 */
 	if (timer->it_process) {
-		if (timer->it_sigev_notify == (SIGEV_SIGNAL|SIGEV_THREAD_ID))
+		if (timer->it_sigev_notify & (SIGEV_SIGNAL | SIGEV_THREAD_ID))
 			put_task_struct(timer->it_process);
 		timer->it_process = NULL;
 	}

@@ -1138,7 +1138,7 @@
 	 * they got something (see the lock code above).
 	 */
 	if (timer->it_process) {
-		if (timer->it_sigev_notify == (SIGEV_SIGNAL|SIGEV_THREAD_ID))
+		if (timer->it_sigev_notify & (SIGEV_SIGNAL | SIGEV_THREAD_ID))
 			put_task_struct(timer->it_process);
 		timer->it_process = NULL;
 	}

What is the purpose of this change? The `good_sigevent' check ensures that if SIGEV_THREAD_ID is set, then the value is exactly SIGEV_SIGNAL|SIGEV_THREAD_ID. In fact, this change has no effect at all because SIGEV_SIGNAL is zero. If it weren't, it would have an undesireable effect of doing the task_struct refcounting all the time instead of only for SIGEV_THREAD_ID. That refcounting is never required in the plain SIGEV_SIGNAL case, because the task_struct pointer stored in the group_leader, and that is never freed before all the posix-timers data structures get cleared out anyway (exit_itimers). It's only required for SIGEV_THREAD_ID, where the target thread might have died before the timer was next examined.

Thanks,
Roland

Hi Roland,
Thanks for answering my mistaken impressions. I saw after I wrote that
SIGEV_SIGNAL == 0 which makes everything work. And I was laboring under the misconception that SIGEV_SIGNAL and SIGEV_THREAD were mutually exclusive which isn't true, one always has SIGEV_SIGNAL if SIGEV_THREAD is set.

Regards,
Joe

In the semantic sense they are mutually exclusive. They are not so in the bitwise sense, because the value is really not a bitmask overall, only the SIGEV_THREAD_ID bit is used that way.

Thanks,
Roland