From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932670AbcHKQfw (ORCPT ); Thu, 11 Aug 2016 12:35:52 -0400 Received: from bhuna.collabora.co.uk ([46.235.227.227]:44861 "EHLO bhuna.collabora.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932301AbcHKQfu (ORCPT ); Thu, 11 Aug 2016 12:35:50 -0400 Subject: Re: [PACTH v1] kernel/hung_task.c: Dump all UNINTERUPTIBLE tasks To: Andrew Morton References: <1470151391-16420-1-git-send-email-robert.foss@collabora.com> <20160810154345.f0c34d0936b0835b541405b0@linux-foundation.org> Cc: adurbin@chromium.org, penguin-kernel@I-love.SAKURA.ne.jp, linux-kernel@vger.kernel.org From: Robert Foss Message-ID: <9a55596a-7176-cf88-243d-ad599b6b421f@collabora.com> Date: Thu, 11 Aug 2016 12:35:44 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.2.0 MIME-Version: 1.0 In-Reply-To: <20160810154345.f0c34d0936b0835b541405b0@linux-foundation.org> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2016-08-10 06:43 PM, Andrew Morton wrote: > On Tue, 2 Aug 2016 11:23:11 -0400 robert.foss@collabora.com wrote: > >> From: Aaron Durbin >> >> When the panic path is taken for khungtaskd dump all >> tasks with the UNINTERUPTIBLE state. That way, any >> inter-dependent tasks that caused one another to hang >> will be saved in the crash output. >> >> ... >> >> --- a/kernel/hung_task.c >> +++ b/kernel/hung_task.c >> @@ -122,6 +122,8 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout) >> touch_nmi_watchdog(); >> >> if (sysctl_hung_task_panic) { >> + /* Dump all tasks. */ >> + show_state_filter(TASK_UNINTERRUPTIBLE); >> trigger_all_cpu_backtrace(); >> panic("hung_task: blocked tasks"); >> } > > Well, it's going to produce more gunk for the operator to read through > and understand. > > I'd like to hear a little more about the value of this change: what > particular problem prompted it, etc. > It would indeed provide more gunk. What makes it useful is that is on enabled by default and enables rapid debugging of devices that are not physically accessible or accessible for debugging otherwise. So the primary usecase would be when a user of a device is seeing some issues and submits the logs from the device. Without any further action from the user, the problem could potentially be solved.