From mboxrd@z Thu Jan 1 00:00:00 1970 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753335AbeAJSmC (ORCPT + 1 other); Wed, 10 Jan 2018 13:42:02 -0500 Received: from mail.kernel.org ([198.145.29.99]:57732 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752785AbeAJSmA (ORCPT ); Wed, 10 Jan 2018 13:42:00 -0500 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 614CE20834 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=goodmis.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=rostedt@goodmis.org Date: Wed, 10 Jan 2018 13:41:57 -0500 From: Steven Rostedt To: Tejun Heo Cc: Petr Mladek , Sergey Senozhatsky , 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@home.goodmis.org, Byungchul Park , Sergey Senozhatsky , Pavel Machek , linux-kernel@vger.kernel.org Subject: Re: [PATCH v5 0/2] printk: Console owner and waiter logic cleanup Message-ID: <20180110134157.1c3ce4b9@vmware.local.home> In-Reply-To: <20180110181252.GK3668920@devbig577.frc2.facebook.com> References: <20180110132418.7080-1-pmladek@suse.com> <20180110140547.GZ3668920@devbig577.frc2.facebook.com> <20180110130517.6ff91716@vmware.local.home> <20180110181252.GK3668920@devbig577.frc2.facebook.com> X-Mailer: Claws Mail 3.15.1 (GTK+ 2.24.31; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: On Wed, 10 Jan 2018 10:12:52 -0800 Tejun Heo wrote: > Hello, Steven. > > So, everything else on your message, sure. You do what you have to > do, but I really don't understand the following part, and this has > been the main source of frustration in the whole discussion. > > On Wed, Jan 10, 2018 at 01:05:17PM -0500, Steven Rostedt wrote: > > You on the other hand are showing unrealistic scenarios, and crying > > that it's what you see in production, with no proof of it. > > I've explained the same scenario multiple times. Unless you're > assuming that I'm lying, it should be amply clear that the scenario is > unrealistic - we've been seeing them taking place repeatedly for quite > a while. The one scenario you did show was the recursive OOM messages, and as Peter Zijlstra pointed out that's more of a bug in the net console than a printk bug. > > What I don't understand is why we can't address this seemingly obvious > problem. If there are technical reasons and the consensus is to not > solve this within flushing logic, sure, we can deal with it otherwise, > but we at least have to be able to agree that there are actual issues > here, no? The issue with the solution you want to do with printk is that it can break existing printk usages. As Petr said, people want printk to do two things. 1 - print out data ASAP, 2 - not lock up the system. The two are fighting each other. You care more about 2 where I (and others, like Peter Zijlstra and Linus) care more about 1. My solution can help with 2 without doing anything to hurt 1. You are NACKing my solution because it doesn't solve this bug with net console. I believe net console should be fixed. You believe that printk should have a work around to not let net console type bugs occur. Which to me is papering over the real bugs. -- Steve From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f70.google.com (mail-pg0-f70.google.com [74.125.83.70]) by kanga.kvack.org (Postfix) with ESMTP id C6A906B0033 for ; Wed, 10 Jan 2018 13:42:01 -0500 (EST) Received: by mail-pg0-f70.google.com with SMTP id f8so11921694pgs.9 for ; Wed, 10 Jan 2018 10:42:01 -0800 (PST) Received: from mail.kernel.org (mail.kernel.org. [198.145.29.99]) by mx.google.com with ESMTPS id f64si12516602plf.473.2018.01.10.10.42.00 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 10 Jan 2018 10:42:00 -0800 (PST) Date: Wed, 10 Jan 2018 13:41:57 -0500 From: Steven Rostedt Subject: Re: [PATCH v5 0/2] printk: Console owner and waiter logic cleanup Message-ID: <20180110134157.1c3ce4b9@vmware.local.home> In-Reply-To: <20180110181252.GK3668920@devbig577.frc2.facebook.com> References: <20180110132418.7080-1-pmladek@suse.com> <20180110140547.GZ3668920@devbig577.frc2.facebook.com> <20180110130517.6ff91716@vmware.local.home> <20180110181252.GK3668920@devbig577.frc2.facebook.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Tejun Heo Cc: Petr Mladek , Sergey Senozhatsky , 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@home.goodmis.org, Byungchul Park , Sergey Senozhatsky , Pavel Machek , linux-kernel@vger.kernel.org On Wed, 10 Jan 2018 10:12:52 -0800 Tejun Heo wrote: > Hello, Steven. > > So, everything else on your message, sure. You do what you have to > do, but I really don't understand the following part, and this has > been the main source of frustration in the whole discussion. > > On Wed, Jan 10, 2018 at 01:05:17PM -0500, Steven Rostedt wrote: > > You on the other hand are showing unrealistic scenarios, and crying > > that it's what you see in production, with no proof of it. > > I've explained the same scenario multiple times. Unless you're > assuming that I'm lying, it should be amply clear that the scenario is > unrealistic - we've been seeing them taking place repeatedly for quite > a while. The one scenario you did show was the recursive OOM messages, and as Peter Zijlstra pointed out that's more of a bug in the net console than a printk bug. > > What I don't understand is why we can't address this seemingly obvious > problem. If there are technical reasons and the consensus is to not > solve this within flushing logic, sure, we can deal with it otherwise, > but we at least have to be able to agree that there are actual issues > here, no? The issue with the solution you want to do with printk is that it can break existing printk usages. As Petr said, people want printk to do two things. 1 - print out data ASAP, 2 - not lock up the system. The two are fighting each other. You care more about 2 where I (and others, like Peter Zijlstra and Linus) care more about 1. My solution can help with 2 without doing anything to hurt 1. You are NACKing my solution because it doesn't solve this bug with net console. I believe net console should be fixed. You believe that printk should have a work around to not let net console type bugs occur. Which to me is papering over the real bugs. -- Steve -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. 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