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=-9.9 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,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 71A94C2D0A8 for ; Mon, 28 Sep 2020 07:32:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F220D20809 for ; Mon, 28 Sep 2020 07:32:22 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="aZUJAjjm" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726630AbgI1HcW (ORCPT ); Mon, 28 Sep 2020 03:32:22 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60084 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726440AbgI1HcV (ORCPT ); Mon, 28 Sep 2020 03:32:21 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1339CC0613CE for ; Mon, 28 Sep 2020 00:32:21 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.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=9a4RQ/cVE8L9jRWNlJ9jl2x1mUr9n344j0WMZjuDA5s=; b=aZUJAjjmdP/OsenQWBHc6mHLmD wUWPfx0OuGGuItQ8dnzsPdhenqd0uKm2ziu731VRm3PGPK1Ajck7Rod1Xag7kANv3RJrg+TDQrR7q 4uXD2+FaPtg9dqtPeeqnLlIdUMY8hncZygc8hy8284KxTntU8ImrhrmCoXG1LGpW8qDsWOm0vhfMt /oXesj5Rf2hfbjpWIkfAv/72ZyuCoaH7nicXiY2A7O9dyeUQftM50dzmttUpdmqruGs2MyF6fNdV8 RmT8/tiGtY4sYeGyXRHSMcaKoolyZTKnWr+vL2v6UmB9Qj/JUOB3YNgdIVh4v6LHS14yfBP4SzSOz jSedQIeQ==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1kMndm-0007Qh-PS; Mon, 28 Sep 2020 07:32:07 +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 5CDE9300F7A; Mon, 28 Sep 2020 09:32:03 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 0AB142019499B; Mon, 28 Sep 2020 09:32:03 +0200 (CEST) Date: Mon, 28 Sep 2020 09:32:02 +0200 From: Peter Zijlstra To: 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 Subject: Re: [PATCH 2/2] sched: mark PRINTK_DEFERRED_CONTEXT_MASK in __schedule() Message-ID: <20200928073202.GA2611@hirez.programming.kicks-ass.net> References: <20200927161130.33172-1-zhouchengming@bytedance.com> <20200927161130.33172-2-zhouchengming@bytedance.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200927161130.33172-2-zhouchengming@bytedance.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. It also shouldn't happen in the first place, so who bloody cares. > Signed-off-by: Chengming Zhou > Signed-off-by: Muchun Song > --- > kernel/sched/core.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index 2d95dc3f4644..81d8bf614225 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -4444,6 +4444,7 @@ static void __sched notrace __schedule(bool preempt) > */ > rq_lock(rq, &rf); > smp_mb__after_spinlock(); > + printk_deferred_enter(); > > /* Promote REQ to ACT */ > rq->clock_update_flags <<= 1; > @@ -4530,6 +4531,7 @@ static void __sched notrace __schedule(bool preempt) > rq_unlock_irq(rq, &rf); > } > > + printk_deferred_exit(); > balance_callback(rq); > } NAK printk_deferred is an abomination, kill that.