From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754584Ab3FFUog (ORCPT ); Thu, 6 Jun 2013 16:44:36 -0400 Received: from mail-pa0-f53.google.com ([209.85.220.53]:32768 "EHLO mail-pa0-f53.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752871Ab3FFUoc (ORCPT ); Thu, 6 Jun 2013 16:44:32 -0400 Date: Thu, 6 Jun 2013 13:44:28 -0700 From: Tejun Heo To: Eric Dumazet Cc: greearb@candelatech.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH] Fix lockup related to stop_machine being stuck in __do_softirq. Message-ID: <20130606204428.GA5045@htj.dyndns.org> References: <1370492751-6886-1-git-send-email-greearb@candelatech.com> <1370492994.24311.331.camel@edumazet-glaptop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1370492994.24311.331.camel@edumazet-glaptop> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jun 05, 2013 at 09:29:54PM -0700, Eric Dumazet wrote: > On Wed, 2013-06-05 at 21:25 -0700, greearb@candelatech.com wrote: > > From: Ben Greear > > > diff --git a/kernel/softirq.c b/kernel/softirq.c > > index 14d7758..f150ad6 100644 > > --- a/kernel/softirq.c > > +++ b/kernel/softirq.c > > @@ -204,6 +204,7 @@ EXPORT_SYMBOL(local_bh_enable_ip); > > * should not be able to lock up the box. > > Could you update the comment ? > > I had the following : > > - * We restart softirq processing for at most 2 ms, > - * and if need_resched() is not set. > + * We restart softirq processing for at most MAX_SOFTIRQ_RESTART times, > + * but break the loop if need_resched() is set or after 2 ms. It'd be nice to briefly explain why both protections are necessary in the comment and maybe cite this thread. Also, please cc Linus when posting the next round and I think we still want to find out what's going on with infinite softirq, I'll reply in the original thread. Thanks a lot! -- tejun