From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932445AbdCWMB6 (ORCPT ); Thu, 23 Mar 2017 08:01:58 -0400 Received: from mx2.suse.de ([195.135.220.15]:34284 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753759AbdCWMBz (ORCPT ); Thu, 23 Mar 2017 08:01:55 -0400 Date: Thu, 23 Mar 2017 13:01:52 +0100 From: Petr Mladek To: Peter Zijlstra Cc: Sergey Senozhatsky , Steven Rostedt , Andrew Morton , Linus Torvalds , "Rafael J . Wysocki" , linux-kernel@vger.kernel.org, Sergey Senozhatsky Subject: Re: [RFC][PATCH 0/4] printk: introduce printing kernel thread Message-ID: <20170323120152.GH4008@pathway.suse.cz> References: <20170306124554.828-1-sergey.senozhatsky@gmail.com> <20170322175920.bcltzwega6dts2n4@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170322175920.bcltzwega6dts2n4@hirez.programming.kicks-ass.net> 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 2017-03-22 18:59:20, Peter Zijlstra wrote: > On Mon, Mar 06, 2017 at 09:45:50PM +0900, Sergey Senozhatsky wrote: > > sysrq is potentially even trickier. can we always wake_up() kernel > > thread from sysrq? there probably might be cases when we can't rely > > on the scheduler. > > sysrq runs from interrupt context, right? Should be able to do wakeups. It would make sense to actually switch to the old mode when handling sysrq. At least for some requests that are used for debugging when the system is not responsible. It is pity that it is the irq context that is prone to softlocks. But this might be the only way to actually see the messages. Tetsuo already suggested to use the old mode for SysRq-t, see https://lkml.kernel.org/r/201612261954.FJE69201.OFLVtFJSQFOHMO@I-love.SAKURA.ne.jp Best Regards, Petr