From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-11.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8397AC2D0A8 for ; Mon, 28 Sep 2020 07:52:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3813E21775 for ; Mon, 28 Sep 2020 07:52:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726743AbgI1Hwv (ORCPT ); Mon, 28 Sep 2020 03:52:51 -0400 Received: from smtprelay0173.hostedemail.com ([216.40.44.173]:46706 "EHLO smtprelay.hostedemail.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726657AbgI1Hwu (ORCPT ); Mon, 28 Sep 2020 03:52:50 -0400 Received: from smtprelay.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by smtpgrave06.hostedemail.com (Postfix) with ESMTP id 6F562800BE82 for ; Mon, 28 Sep 2020 07:52:49 +0000 (UTC) Received: from filter.hostedemail.com (clb03-v110.bra.tucows.net [216.40.38.60]) by smtprelay07.hostedemail.com (Postfix) with ESMTP id 5652A181D3030; Mon, 28 Sep 2020 07:52:48 +0000 (UTC) X-Session-Marker: 6A6F6540706572636865732E636F6D X-HE-Tag: floor73_2d0ce722717f X-Filterd-Recvd-Size: 3557 Received: from XPS-9350.home (unknown [47.151.133.149]) (Authenticated sender: joe@perches.com) by omf19.hostedemail.com (Postfix) with ESMTPA; Mon, 28 Sep 2020 07:52:46 +0000 (UTC) Message-ID: <0e8e87e25c90339fe790252626855cbb47bc2c08.camel@perches.com> Subject: Re: [PATCH 2/2] sched: mark PRINTK_DEFERRED_CONTEXT_MASK in __schedule() From: Joe Perches To: Peter Zijlstra , Chengming Zhou Cc: linux-kernel@vger.kernel.org, pmladek@suse.com, sergey.senozhatsky@gmail.com, rostedt@goodmis.org, mingo@redhat.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, bsegall@google.com, mgorman@suse.de, songmuchun@bytedance.com Date: Mon, 28 Sep 2020 00:52:44 -0700 In-Reply-To: <20200928073202.GA2611@hirez.programming.kicks-ass.net> References: <20200927161130.33172-1-zhouchengming@bytedance.com> <20200927161130.33172-2-zhouchengming@bytedance.com> <20200928073202.GA2611@hirez.programming.kicks-ass.net> Content-Type: text/plain; charset="ISO-8859-1" User-Agent: Evolution 3.36.4-0ubuntu1 MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2020-09-28 at 09:32 +0200, Peter Zijlstra wrote: > On Mon, Sep 28, 2020 at 12:11:30AM +0800, Chengming Zhou wrote: > > The WARN_ON/WARN_ON_ONCE with rq lock held in __schedule() should be > > deferred by marking the PRINTK_DEFERRED_CONTEXT_MASK, or will cause > > deadlock on rq lock in the printk path. [] > NAK printk_deferred is an abomination, kill that. Didn't you introduce it? Should you be complaining to yourself? --- commit 3ccf3e8306156a28213adc720aba807e9a901ad5 Author: Peter Zijlstra Date: Mon Feb 27 10:47:00 2012 +0100 printk/sched: Introduce special printk_sched() for those awkward moments There's a few awkward printk()s inside of scheduler guts that people prefer to keep but really are rather deadlock prone. Fudge around it by storing the text in a per-cpu buffer and poll it using the existing printk_tick() handler. This will drop output when its more frequent than once a tick, however only the affinity thing could possible go that fast and for that just one should suffice to notify the admin he's done something silly.. Signed-off-by: Peter Zijlstra Cc: Linus Torvalds Cc: Andrew Morton Link: http://lkml.kernel.org/n/tip-wua3lmkt3dg8nfts66o6brne@git.kernel.org Signed-off-by: Ingo Molnar commit aac74dc495456412c4130a1167ce4beb6c1f0b38 Author: John Stultz Date: Wed Jun 4 16:11:40 2014 -0700 printk: rename printk_sched to printk_deferred After learning we'll need some sort of deferred printk functionality in the timekeeping core, Peter suggested we rename the printk_sched function so it can be reused by needed subsystems. This only changes the function name. No logic changes. Signed-off-by: John Stultz Reviewed-by: Steven Rostedt Cc: Jan Kara Cc: Peter Zijlstra Cc: Jiri Bohac Cc: Thomas Gleixner Cc: Ingo Molnar Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds