From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754065AbeDWFfn (ORCPT ); Mon, 23 Apr 2018 01:35:43 -0400 Received: from mail-pg0-f67.google.com ([74.125.83.67]:34096 "EHLO mail-pg0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751117AbeDWFfg (ORCPT ); Mon, 23 Apr 2018 01:35:36 -0400 X-Google-Smtp-Source: AIpwx4+6wCrpn+/rStQibRD2+wDWEc9kcUuQIZffH3pTaCUh2zDb5ZkgCYJMUMeUOujt5rtpMiVOtQ== Date: Mon, 23 Apr 2018 14:35:31 +0900 From: Sergey Senozhatsky To: Tejun Heo Cc: Steven Rostedt , Sergey Senozhatsky , Sergey Senozhatsky , Petr Mladek , akpm@linux-foundation.org, linux-mm@kvack.org, Cong Wang , Dave Hansen , Johannes Weiner , Mel Gorman , Michal Hocko , Vlastimil Babka , Peter Zijlstra , Linus Torvalds , Jan Kara , Mathieu Desnoyers , Tetsuo Handa , rostedt@rostedt.homelinux.com, Byungchul Park , Pavel Machek , linux-kernel@vger.kernel.org Subject: Re: [PATCH v5 0/2] printk: Console owner and waiter logic cleanup Message-ID: <20180423053531.GB3643@jagdpanzerIV> References: <20180117134201.0a9cbbbf@gandalf.local.home> <20180119132052.02b89626@gandalf.local.home> <20180120071402.GB8371@jagdpanzerIV> <20180120104931.1942483e@gandalf.local.home> <20180121141521.GA429@tigerII.localdomain> <20180123064023.GA492@jagdpanzerIV> <20180123095652.5e14da85@gandalf.local.home> <20180123152130.GB429@tigerII.localdomain> <20180123104121.2ef96d81@gandalf.local.home> <20180123154347.GE1771050@devbig577.frc2.facebook.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180123154347.GE1771050@devbig577.frc2.facebook.com> User-Agent: Mutt/1.9.5 (2018-04-13) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On (01/23/18 07:43), Tejun Heo wrote: > > > > We can have more. But if printk is causing printks, that's a major bug. > > And work queues are not going to fix it, it will just spread out the > > pain. Have it be 100 printks, it needs to be fixed if it is happening. > > And having all printks just generate more printks is not helpful. Even > > if we slow them down. They will still never end. > > So, at least in the case that we were seeing, it isn't that black and > white. printk keeps causing printks but only because printk buffer > flushing is preventing the printk'ing context from making forward > progress. The key problem there is that a flushing context may get > pinned flushing indefinitely and using a separate context does solve > the problem. Hello Tejun, I'm willing to take a look at those printk()-s from console drivers. Any chance you can send me some of the backtraces you see [the most common/disturbing]? -ss