Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753216AbYB1FFg (ORCPT ); Thu, 28 Feb 2008 00:05:36 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750755AbYB1FF3 (ORCPT ); Thu, 28 Feb 2008 00:05:29 -0500 Received: from E23SMTP06.au.ibm.com ([202.81.18.175]:32894 "EHLO e23smtp06.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750739AbYB1FF2 (ORCPT ); Thu, 28 Feb 2008 00:05:28 -0500 Date: Thu, 28 Feb 2008 10:35:08 +0530 From: Gautham R Shenoy To: "Paul E. McKenney" Cc: linux-kernel@vger.kernel.org, hidave.darkstar@gmail.com, akpm@linux-foundation.org, fzu@wemgehoertderstaat.de, mingo@elte.hu, dipankar@in.ibm.com, niv@us.ibm.com, dvhltc@us.ibm.com Subject: Re: [PATCH] Fix hibernate/resume in presence of PREEMPT_RCU and hotplug Message-ID: <20080228050507.GA31289@in.ibm.com> Reply-To: ego@in.ibm.com References: <20080228002110.GA20091@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080228002110.GA20091@linux.vnet.ibm.com> User-Agent: Mutt/1.5.15+20070412 (2007-04-11) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1709 Lines: 48 On Wed, Feb 27, 2008 at 04:21:10PM -0800, Paul E. McKenney wrote: > Hello! > > This fixes a oops encountered when doing hibernate/resume in presence > of PREEMPT_RCU. The problem was that the code failed to disable preemption > when accessing a per-CPU variable. This is OK when called from code > that already has preemption disabled, but such is not the case from > the suspend/resume code path. Well, rcu_offline_cpu() is called from the cpu-offline callback path, and AFAICS, it doesn't disable preemption. I wonder how we're seeing this only now! Indeed a good catch! Reviewed-by: Gautham R Shenoy > > Reported-by: Dave Young > Tested-by: Dave Young > Signed-off-by: Paul E. McKenney > --- > > rcupreempt.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff -urpNa -X dontdiff linux-2.6.25-rc3/kernel/rcupreempt.c linux-2.6.25-rc3-rcuoffline/kernel/rcupreempt.c > --- linux-2.6.25-rc3/kernel/rcupreempt.c 2008-02-26 16:58:43.000000000 -0800 > +++ linux-2.6.25-rc3-rcuoffline/kernel/rcupreempt.c 2008-02-26 17:04:17.000000000 -0800 > @@ -702,8 +702,9 @@ void rcu_offline_cpu(int cpu) > * fix. > */ > > + local_irq_save(flags); > rdp = RCU_DATA_ME(); > - spin_lock_irqsave(&rdp->lock, flags); > + spin_lock(&rdp->lock); > *rdp->nexttail = list; > if (list) > rdp->nexttail = tail; -- Thanks and Regards gautham -- 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/