From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754899AbbKCPQ6 (ORCPT ); Tue, 3 Nov 2015 10:16:58 -0500 Received: from mx1.redhat.com ([209.132.183.28]:35172 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751568AbbKCPQy (ORCPT ); Tue, 3 Nov 2015 10:16:54 -0500 From: Ulrich Obergfell To: linux-kernel@vger.kernel.org Cc: akpm@linux-foundation.org, dzickus@redhat.com, atomlin@redhat.com, uobergfe@redhat.com Subject: [PATCH 4/4] watchdog: fix race between proc_watchdog_thresh() and watchdog_timer_fn() Date: Tue, 3 Nov 2015 16:21:01 +0100 Message-Id: <1446564061-3379-5-git-send-email-uobergfe@redhat.com> In-Reply-To: <1446564061-3379-1-git-send-email-uobergfe@redhat.com> References: <1446564061-3379-1-git-send-email-uobergfe@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Theoretically it is possible that the watchdog timer expires right at the time when a user sets 'watchdog_thresh' to zero (note: this disables the lockup detectors). In this scenario, the is_softlockup() function - which is called by the timer - could produce a false positive. Fix this by checking the current value of 'watchdog_thresh'. Signed-off-by: Ulrich Obergfell --- kernel/watchdog.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/watchdog.c b/kernel/watchdog.c index 84c4744..18f34cf 100644 --- a/kernel/watchdog.c +++ b/kernel/watchdog.c @@ -289,7 +289,7 @@ static int is_softlockup(unsigned long touch_ts) { unsigned long now = get_timestamp(); - if (watchdog_enabled & SOFT_WATCHDOG_ENABLED) { + if ((watchdog_enabled & SOFT_WATCHDOG_ENABLED) && watchdog_thresh){ /* Warn about unreasonable delays. */ if (time_after(now, touch_ts + get_softlockup_thresh())) return now - touch_ts; -- 1.7.11.7