linux-kernel - [PATCH 3/4] posix timers: timer_delete: remove the bogus "->it

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Date:	Sat, 3 May 2008 21:35:53 +0400
From:	Oleg Nesterov <oleg@...sign.ru>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Austin Clements <amdragon+kernelbugzilla@....edu>,
	Ingo Molnar <mingo@...e.hu>, john stultz <johnstul@...ibm.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Michael Kerrisk <mtk.manpages@...glemail.com>,
	Roland McGrath <roland@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org
Subject: [PATCH 3/4] posix timers: timer_delete: remove the bogus "->it_process != NULL" check

sys_timer_delete() and itimer_delete() check "timer->it_process != NULL", this
looks completely bogus. ->it_process == NULL means that this timer is already
under destruction or it is not fully initialized, this must not happen.

	sys_timer_delete: the timer is locked, and lock_timer() can't succeed
	if ->it_process == NULL.

	itimer_delete: it is called by exit_itimers() when there are no other
	threads which can play with signal_struct->posix_timers.

Signed-off-by: Oleg Nesterov <oleg@...sign.ru>

--- 25/kernel/posix-timers.c~3_TDEL_NO_CHECK	2008-04-24 16:52:11.000000000 +0400
+++ 25/kernel/posix-timers.c	2008-05-03 19:55:27.000000000 +0400
@@ -855,11 +855,10 @@ retry_delete:
 	 * This keeps any tasks waiting on the spin lock from thinking
 	 * they got something (see the lock code above).
 	 */
-	if (timer->it_process) {
-		if (timer->it_sigev_notify == (SIGEV_SIGNAL|SIGEV_THREAD_ID))
-			put_task_struct(timer->it_process);
-		timer->it_process = NULL;
-	}
+	if (timer->it_sigev_notify == (SIGEV_SIGNAL|SIGEV_THREAD_ID))
+		put_task_struct(timer->it_process);
+	timer->it_process = NULL;
+
 	unlock_timer(timer, flags);
 	release_posix_timer(timer, IT_ID_SET);
 	return 0;
@@ -884,11 +883,10 @@ retry_delete:
 	 * This keeps any tasks waiting on the spin lock from thinking
 	 * they got something (see the lock code above).
 	 */
-	if (timer->it_process) {
-		if (timer->it_sigev_notify == (SIGEV_SIGNAL|SIGEV_THREAD_ID))
-			put_task_struct(timer->it_process);
-		timer->it_process = NULL;
-	}
+	if (timer->it_sigev_notify == (SIGEV_SIGNAL|SIGEV_THREAD_ID))
+		put_task_struct(timer->it_process);
+	timer->it_process = NULL;
+
 	unlock_timer(timer, flags);
 	release_posix_timer(timer, IT_ID_SET);
 }

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