From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752767AbYKSLIP (ORCPT ); Wed, 19 Nov 2008 06:08:15 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751657AbYKSLH6 (ORCPT ); Wed, 19 Nov 2008 06:07:58 -0500 Received: from ug-out-1314.google.com ([66.249.92.173]:49971 "EHLO ug-out-1314.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751328AbYKSLH5 (ORCPT ); Wed, 19 Nov 2008 06:07:57 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:in-reply-to:user-agent; b=LJRNd4YLNY94UGy2hEBeUrMaXGMhwnnsgmlTEA331TPosQyjr0kQWuzItnVcUEMC5Q /y9c3mOV4GCFBTTIvty8gCccHMwLlcAzq85VaCKTEpiI7FCDfm9w+d+sCgwNB+1/8tp7 xw6zZb8eITm9UAEC2nWnN8wFjyCg8h66rv71k= Date: Wed, 19 Nov 2008 11:07:48 +0000 From: Jarek Poplawski To: Ingo Molnar Cc: Johannes Berg , David Miller , Ferenc Wagner , netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] softirq: Fix warnings triggered by netconsole Message-ID: <20081119110748.GA7557@ff.dom.local> References: <87y6zwwy5c.fsf@tac.ki.iif.hu> <20081119084125.GB6699@ff.dom.local> <20081119093224.GE22309@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20081119093224.GE22309@elte.hu> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Nov 19, 2008 at 10:32:24AM +0100, Ingo Molnar wrote: > > * Jarek Poplawski wrote: > > > Consider netconsole case as special in local_bh_enable()/_disable(). > > This patch skips in_irq() and irqs_disabled() warnings for NETPOLL > > configs when it's safe wrt. do_softirq(). > > > > Reported-by: Ferenc Wagner > > Signed-off-by: Jarek Poplawski > > --- > > [apply on top of my first softirq patch in this thread] > > > > diff -Nurp a/kernel/softirq.c b/kernel/softirq.c > > --- a/kernel/softirq.c 2008-11-19 07:33:23.000000000 +0000 > > +++ b/kernel/softirq.c 2008-11-19 07:26:28.000000000 +0000 > > @@ -76,7 +76,12 @@ static void __local_bh_disable(unsigned > > { > > unsigned long flags; > > > > +#ifdef CONFIG_NETPOLL > > + if (!softirq_count()) > > + WARN_ON_ONCE(in_irq()); > > +#else > > WARN_ON_ONCE(in_irq()); > > +#endif > > > > raw_local_irq_save(flags); > > add_preempt_count(SOFTIRQ_OFFSET); > > @@ -138,7 +143,16 @@ static inline void _local_bh_enable_ip(u > > #ifdef CONFIG_TRACE_IRQFLAGS > > unsigned long flags; > > #endif > > +#ifdef CONFIG_NETPOLL > > + /* > > + * Special-case - netconsole runs network code with all interrupts > > + * disabled. Warn only if it can be really dangerous: > > + */ > > + if (softirq_count() == SOFTIRQ_OFFSET) > > + WARN_ON_ONCE(in_irq() || irqs_disabled()); > > +#else > > WARN_ON_ONCE(in_irq() || irqs_disabled()); > > +#endif > > #ifdef CONFIG_TRACE_IRQFLAGS > > local_irq_save(flags); > > #endif > > this is a very ugly patch, not really acceptable. Well, it's a question of taste. Anyway, this patch is only about warnings, so no big deal. But I still think the first patch reverting local_irq_save() -> local_irq_disable() change should be applied. There is no need to give users any additional lockups risk while we know there are unsolved issues. BTW, the current situation with: local_irq_disable() in _local_bh_enable() and local_irq_save() in do_softirq() doesn't make much sense. I know, there is local_irq_disable() in __do_softirq() again, but it can be often skipped on this path because of in_interrupt() test (and there is soon this local_irq_restore() in do_softirq()). Jarek P.