Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751390AbaLESPU (ORCPT ); Fri, 5 Dec 2014 13:15:20 -0500 Received: from mail-qg0-f46.google.com ([209.85.192.46]:58162 "EHLO mail-qg0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750862AbaLESPS (ORCPT ); Fri, 5 Dec 2014 13:15:18 -0500 MIME-Version: 1.0 In-Reply-To: <5481C92E.6020805@oracle.com> References: <20141127225637.GA24019@redhat.com> <547b8a45.6e608c0a.20f9.1002@mx.google.com> <547bbe36.48548c0a.105c.779c@mx.google.com> <20141201191431.GA17385@linux.vnet.ibm.com> <547ccf74.a5198c0a.25de.26d9@mx.google.com> <20141201230339.GA20487@ret.masoncoding.com> <20141202193252.GB17595@redhat.com> <547E4C14.6040509@oracle.com> <54813C03.8040009@oracle.com> <5481C92E.6020805@oracle.com> Date: Fri, 5 Dec 2014 10:15:17 -0800 X-Google-Sender-Auth: nM2CVXblQ3RPRyHWXbJw6uYv6gc Message-ID: Subject: Re: frequent lockups in 3.18rc4 From: Linus Torvalds To: Sasha Levin Cc: Dave Jones , Chris Mason , =?UTF-8?Q?D=C3=A2niel_Fraga?= , "Paul E. McKenney" , Linux Kernel Mailing List Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Dec 5, 2014 at 7:03 AM, Sasha Levin wrote: > > Yes, it's going to a serial line, but it's only about 100 lines/second on > average. I wouldn't expect it to cause anything to hang! A regular 16650 serial chip? Running at 115kbps, I assume? So that's about 11kB/s. And the serial console is polling, since it can't sleep or depend on interrupts. At a average line length of what, 40 characters? At less than 300 lines/s, you'd be using up 100% of one CPU. And since the printouts are serialized, that would be all other CPU's too.. 100 lines/s _average_ means that I can easily see it be 300lines/s for a while. So yeah. The serial console is simply not designed to handle continuous output. It's for the "occasional" stuff. The fact that your rcu lockups go away when you make the fault injection be quiet makes me really suspect this is related. Linus -- 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/