Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753780Ab1FFJCR (ORCPT ); Mon, 6 Jun 2011 05:02:17 -0400 Received: from casper.infradead.org ([85.118.1.10]:50524 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752663Ab1FFJCP convert rfc822-to-8bit (ORCPT ); Mon, 6 Jun 2011 05:02:15 -0400 Subject: Re: [debug patch] printk: Add a printk killswitch to robustify NMI watchdog messages From: Peter Zijlstra To: Arne Jansen Cc: Ingo Molnar , Linus Torvalds , mingo@redhat.com, hpa@zytor.com, linux-kernel@vger.kernel.org, efault@gmx.de, npiggin@kernel.dk, akpm@linux-foundation.org, frank.rowand@am.sony.com, tglx@linutronix.de, linux-tip-commits@vger.kernel.org In-Reply-To: <4DEBE3DF.70104@die-jansens.de> References: <20110605151323.GA30590@elte.hu> <20110605152641.GA31124@elte.hu> <20110605153218.GA31471@elte.hu> <4DEBA9CC.4090503@die-jansens.de> <4DEBB05C.8090506@die-jansens.de> <4DEBB3DA.8060001@die-jansens.de> <20110605172052.GA1036@elte.hu> <4DEBBFF9.2030101@die-jansens.de> <20110605185957.GA3452@elte.hu> <4DEBD95B.6030901@die-jansens.de> <20110605194419.GA12965@elte.hu> <4DEBE3DF.70104@die-jansens.de> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT Date: Mon, 06 Jun 2011 11:01:49 +0200 Message-ID: <1307350909.2353.7408.camel@twins> Mime-Version: 1.0 X-Mailer: Evolution 2.30.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1047 Lines: 31 On Sun, 2011-06-05 at 22:15 +0200, Arne Jansen wrote: > > Can lockdep just get confused by the lockdep_off/on calls in printk > while scheduling is allowed? There aren't many users of lockdep_off(). Yes!, in that case lock_is_held() returns false, triggering the warning. I guess there's an argument to be made in favour of the below.. --- kernel/lockdep.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-) diff --git a/kernel/lockdep.c b/kernel/lockdep.c index 53a6895..e4129cf 100644 --- a/kernel/lockdep.c +++ b/kernel/lockdep.c @@ -3242,7 +3242,7 @@ int lock_is_held(struct lockdep_map *lock) int ret = 0; if (unlikely(current->lockdep_recursion)) - return ret; + return 1; /* avoid false negative lockdep_assert_held */ raw_local_irq_save(flags); check_flags(flags); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/