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=-3.9 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no 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 08300C2D0A8 for ; Mon, 28 Sep 2020 08:06:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8AA0122262 for ; Mon, 28 Sep 2020 08:06:32 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="CLA0jGvl" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726615AbgI1IGb (ORCPT ); Mon, 28 Sep 2020 04:06:31 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37156 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726500AbgI1IGa (ORCPT ); Mon, 28 Sep 2020 04:06:30 -0400 Received: from merlin.infradead.org (merlin.infradead.org [IPv6:2001:8b0:10b:1231::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A21E5C0613CE for ; Mon, 28 Sep 2020 01:06:30 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=nSb+Zj16S/95FquhSwPKCI8PgeOwt43+2Fh6BPMBmGY=; b=CLA0jGvlYBclgRTcwwuxVFFBgn AfbbKySnhTOmpEUZyMMAXItCD6H6/45h94bicfeJ1PrRm+JUuOMfyH/IROHwZZyfWpXx7DQVqZdD9 ZSioSKOUr+JcD1JbXY3o1SCcuEVFmACh0WDjSF/fHd5rDFfB/3veji9cJk7dEkS0q/BJM4MCz171A n/FOGLdbIXzJiL92DN4RC8Agp86fqImQOtOI3NcaZukH5CYndYm4/vO0bLKzSXyMiJ0bRMYIkpRQJ Ggbuy84EDRWa/ah0qPMDiIHXtGw7rmFawYCGeSIYSTAlXP2Fl4uiBwgNnArm/WXzj4YN7nSEbkleI VI1hGdLA==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1kMoAp-0002BI-3z; Mon, 28 Sep 2020 08:06:15 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id BA292302753; Mon, 28 Sep 2020 10:06:13 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 9D0A7200D90B3; Mon, 28 Sep 2020 10:06:13 +0200 (CEST) Date: Mon, 28 Sep 2020 10:06:13 +0200 From: Peter Zijlstra To: Joe Perches Cc: Chengming Zhou , 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 Subject: Re: [PATCH 2/2] sched: mark PRINTK_DEFERRED_CONTEXT_MASK in __schedule() Message-ID: <20200928080613.GB2651@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> <0e8e87e25c90339fe790252626855cbb47bc2c08.camel@perches.com> <20200928080022.GD2611@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200928080022.GD2611@hirez.programming.kicks-ass.net> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Sep 28, 2020 at 10:00:22AM +0200, Peter Zijlstra wrote: > On Mon, Sep 28, 2020 at 12:52:44AM -0700, Joe Perches wrote: > > 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? > > Yeah. I should've hacked around it then I suppose. Still, no reason to > proliferate that crap. Afaik the new printk should be able to deal with > this at some point. > > The thing we're not going to do it add a cache-miss to schedule just > because. Also, using deferred for WARN/BUG is fundamentally wrong, you want that splat _NOW_, there might not be a later.