From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755347AbbBPSUP (ORCPT ); Mon, 16 Feb 2015 13:20:15 -0500 Received: from mail-wg0-f53.google.com ([74.125.82.53]:65430 "EHLO mail-wg0-f53.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753126AbbBPSUN (ORCPT ); Mon, 16 Feb 2015 13:20:13 -0500 From: Frederic Weisbecker To: Peter Zijlstra Cc: LKML , Frederic Weisbecker , Steven Rostedt , Huang Ying , Ingo Molnar Subject: [PATCH] sched: Fix preempt_schedule_common() triggering tracing recursion Date: Mon, 16 Feb 2015 19:20:07 +0100 Message-Id: <1424110807-15057-1-git-send-email-fweisbec@gmail.com> X-Mailer: git-send-email 2.1.4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Since the function graph tracer needs to disable preemption, it might call preempt_schedule() after reenabling it if something triggered the need for rescheduling in between. Therefore we can't trace preempt_schedule() itself because we would face a function tracing recursion otherwise as the tracer is always called before PREEMPT_ACTIVE gets set to prevent that recursion. This is why preempt_schedule() is tagged as "notrace". But the same issue applies to every function called by preempt_schedule() before PREEMPT_ACTIVE is actually set. And preempt_schedule_common() is one such example. Unfortunately we forgot to tag it as notrace as well and as a result we are encountering tracing recursion since it got introduced by a18b5d01819235629289212ad428a5ee2b40f0d9 ("sched: Fix missing preemption opportunity"). Let's fix that by applying the appropriate function tag to preempt_schedule_common(). Reported-by: Huang Ying Acked-by: Steven Rostedt Cc: Huang Ying Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Steven Rostedt Signed-off-by: Frederic Weisbecker --- kernel/sched/core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 13049aa..683e850 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -2899,7 +2899,7 @@ void __sched schedule_preempt_disabled(void) preempt_disable(); } -static void preempt_schedule_common(void) +static void __sched notrace preempt_schedule_common(void) { do { __preempt_count_add(PREEMPT_ACTIVE); -- 2.1.4