From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757604Ab1FGSGy (ORCPT ); Tue, 7 Jun 2011 14:06:54 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:40116 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752495Ab1FGSGx (ORCPT ); Tue, 7 Jun 2011 14:06:53 -0400 Date: Tue, 7 Jun 2011 20:06:38 +0200 From: Ingo Molnar To: Peter Zijlstra Cc: lists@die-jansens.de, mingo@redhat.com, hpa@zytor.com, linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, stable@kernel.org, tglx@linutronix.de, linux-tip-commits@vger.kernel.org Subject: Re: [tip:sched/urgent] lockdep: Fix lock_is_held() on recursion Message-ID: <20110607180638.GB22523@elte.hu> References: <1307398759.2497.966.camel@laptop> <1307450343.2322.250.camel@twins> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1307450343.2322.250.camel@twins> User-Agent: Mutt/1.5.20 (2009-08-17) X-ELTE-SpamScore: -2.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.0 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.3.1 -2.0 BAYES_00 BODY: Bayes spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Peter Zijlstra wrote: > On Tue, 2011-06-07 at 12:02 +0000, tip-bot for Peter Zijlstra wrote: > > Commit-ID: f2513cde93f0957d5dc6c09bc24b0cccd27d8e1d > > Gitweb: http://git.kernel.org/tip/f2513cde93f0957d5dc6c09bc24b0cccd27d8e1d > > Author: Peter Zijlstra > > AuthorDate: Mon, 6 Jun 2011 12:32:43 +0200 > > Committer: Ingo Molnar > > CommitDate: Tue, 7 Jun 2011 12:25:50 +0200 > > > > lockdep: Fix lock_is_held() on recursion > > > > The main lock_is_held() user is lockdep_assert_held(), avoid false > > assertions in lockdep_off() sections by unconditionally reporting the > > lock is taken. > > > > [ the reason this is important is a lockdep_assert_held() in ttwu() > > which triggers a warning under lockdep_off() as in printk() which > > can trigger another wakeup and lock up due to spinlock > > recursion, as reported and heroically debugged by Arne Jansen ] > > > > Reported-and-tested-by: Arne Jansen > > Signed-off-by: Peter Zijlstra > > Cc: Linus Torvalds > > Cc: > > Not _that_ critical for stable since the offending lockdep_assert_held() > doesn't exist in .39, still definitely won't hurt. Correct, the bug was hard enough to find, i didnt want someone else to trigger a similar one. There's numerous lockdep_assert_held() instances all around the tree. Thanks, Ingo