From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dave Jones Subject: Re: ax25_recvmsg lockup Date: Sun, 4 Aug 2013 12:04:17 -0400 Message-ID: <20130804160417.GA987@redhat.com> References: <20130617142803.GB16732@redhat.com> <20130803.134604.508965748339486186.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: netdev@vger.kernel.org To: David Miller Return-path: Received: from mx1.redhat.com ([209.132.183.28]:33659 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753432Ab3HDQEf (ORCPT ); Sun, 4 Aug 2013 12:04:35 -0400 Content-Disposition: inline In-Reply-To: <20130803.134604.508965748339486186.davem@davemloft.net> Sender: netdev-owner@vger.kernel.org List-ID: On Sat, Aug 03, 2013 at 01:46:04PM -0700, David Miller wrote: > From: Dave Jones > Date: Mon, 17 Jun 2013 10:28:03 -0400 > > > With the right arguments from userspace, reading from an ax25 socket > > can spend long enough in the kernel that it triggers the softlockup > > detector. I hit a bunch of these traces in a trinity run that I > > left running over the weekend. > > I looked at this a bunch of times and am still mystified how this > can happen. > > It should be simple to diagnose since I doubt there is any real > AX25 traffic going to these sockets. > > Any chance you can figure out what the arguments are that cause > this problem? That'll probably help a lot, thanks! thinking about this some more, I wonder if it was related to the problems I was seeing where a bunch of concurrent sync()'s would trip up the soft-lockup detector. Perhaps the ax25 code got preempted and the syncs starved the cpu for a while, so when we eventually got back to the ax25 code, the detector decided it hadn't made progress.. I don't know, it sounds a bit far-fetched, but it's all I can think of. Dave