From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1764933AbXLUAbe (ORCPT ); Thu, 20 Dec 2007 19:31:34 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757130AbXLUAbI (ORCPT ); Thu, 20 Dec 2007 19:31:08 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:51539 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756119AbXLUAbG (ORCPT ); Thu, 20 Dec 2007 19:31:06 -0500 Date: Fri, 21 Dec 2007 01:30:35 +0100 From: Ingo Molnar To: Andrew Morton Cc: trond.myklebust@fys.uio.no, tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, linux-kernel@vger.kernel.org Subject: Re: Linux 2.6.24-rc5 x86 architecture no longer Oopses... Message-ID: <20071221003035.GA10123@elte.hu> References: <1198190447.29917.9.camel@heimdal.trondhjem.org> <20071220145415.f737e7f3.akpm@linux-foundation.org> <20071220234759.GA29776@elte.hu> <20071220161934.0f55029a.akpm@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20071220161934.0f55029a.akpm@linux-foundation.org> User-Agent: Mutt/1.5.17 (2007-11-01) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian 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 * Andrew Morton wrote: > On Fri, 21 Dec 2007 00:47:59 +0100 > Ingo Molnar wrote: > > > > __raw_spin_lock(&die.lock); > > > raw_local_save_flags(flags); > > > - die.lock_owner = smp_processor_id(); > > > + die.lock_owner = raw_smp_processor_id(); > > > > we just disabled irqs with raw_local_save_flags(). > > > > raw_local_save_flags() doesn't disable interrupts? argh. Indeed! (I wanted us to fix that misleading name eons ago, to *_save_flags_only(), but some stupid bikeshed painting discussion prevented it from ever happening.) that should have been raw_local_irq_save(flags)! but ... why is it done like that? Why do we first take the die.lock and disable interrupts afterwards? It's highly weird. 64-bit does it all correctly in traps_64.c, so unification will help us out - but so far perhaps the patch below we should do in 2.6.24? Ingo ------------> Subject: x86: fix die() to not be preemptible From: Ingo Molnar Andrew "Eagle Eye" Morton noticed that we use raw_local_save_flags() instead of raw_local_irq_save(flags) in die(). do it correctly - and first disable interrupts, then take the spinlock. Signed-off-by: Ingo Molnar --- arch/x86/kernel/traps_32.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) Index: linux-x86.q/arch/x86/kernel/traps_32.c =================================================================== --- linux-x86.q.orig/arch/x86/kernel/traps_32.c +++ linux-x86.q/arch/x86/kernel/traps_32.c @@ -373,14 +373,13 @@ void die(const char * str, struct pt_reg if (die.lock_owner != raw_smp_processor_id()) { console_verbose(); + raw_local_irq_save(flags); __raw_spin_lock(&die.lock); - raw_local_save_flags(flags); die.lock_owner = smp_processor_id(); die.lock_owner_depth = 0; bust_spinlocks(1); - } - else - raw_local_save_flags(flags); + } else + raw_local_irq_save(flags); if (++die.lock_owner_depth < 3) { unsigned long esp;