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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C47A9C19F28 for ; Wed, 3 Aug 2022 17:15:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236466AbiHCRPA (ORCPT ); Wed, 3 Aug 2022 13:15:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54164 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231966AbiHCRO5 (ORCPT ); Wed, 3 Aug 2022 13:14:57 -0400 Received: from mail-wm1-x32e.google.com (mail-wm1-x32e.google.com [IPv6:2a00:1450:4864:20::32e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 82C0452DF1 for ; Wed, 3 Aug 2022 10:14:56 -0700 (PDT) Received: by mail-wm1-x32e.google.com with SMTP id i128-20020a1c3b86000000b003a3a22178beso1242844wma.3 for ; Wed, 03 Aug 2022 10:14:56 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=/3dZwuNcVuE6d4zZ4aeM7vczIq122Gxcmf/snpYWoTY=; b=mPMYv2iq+jQ125BM8udKcXg+4UXDUxtCzILO4KDgG2s/BTserP7tB3r3NA5sSNeF8s rk6+S5fx5uPlv3ra/ZnGdMNnTlQNdGFBpfJ41cJOOW2aMpTr/iYT39Xm3EX/TR7Bo4lL KnmmITXsvrMEmT1q3pMchyeyttE7Mrr7bmPKq91MNTApqCV21DIfuCNmU5UBdhgyxmZc yFrvKwYcu+g2e7uz9Cs3Or45aP1Wm7zvr+hFyDAGklIcXAgEIAJLUo9EnvpdtipC9+Fp Ggg0A6FSa7vcTAQhiC3yU3PMjRmcyYxH7L0YP7+coxzPBaavyoCIz/n2eHitOO7QHOcO 1xoQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to; bh=/3dZwuNcVuE6d4zZ4aeM7vczIq122Gxcmf/snpYWoTY=; b=UvKMzxPWQmUcZ45qQ7kowTQPYpQpqIaa5kUGyUteRTeDCV1XRuxo5XAOXBkjO4puqY LqpCpPHW0/4a2EwaXXgWiRS8YT0d9v5YQlKq3fxq0StYeguy8qM+a2YrEru97QPub2DA BzFYNj/q2dfQmVv1+j7qyvZrJafaMVQUmBOzLzID/pko/KECqKocgBQ0rn4HjjBRn++C NWDZq9L+5dA2jh0lVhQiVKi0MuIPeEchcZMB+g0drkSxN5GzJ3LTwtXtBVnNrpDEMt6x yn2dvcZjhFmvjuA4YbvmWA74eK7rdzhE3TIX7SPQXI2EnAvFparWyPm/H4OtkDZlt57u uiQg== X-Gm-Message-State: ACgBeo3nigL8r31H95cQuPOTb0FsNc6LknNNqS5xSs1V0PGrICfX4aF3 1w292KK0CtEkxIBwmZprfZE= X-Google-Smtp-Source: AA6agR5+RQSgYBJ0NnS/al6TqBCjjlkbnQCxVl7Uvy5WWLOldcxAvdFQeWzPgyNRhGVwpiqbpD8hTQ== X-Received: by 2002:a05:600c:1d1b:b0:3a3:e2:42d1 with SMTP id l27-20020a05600c1d1b00b003a300e242d1mr3547004wms.137.1659546895132; Wed, 03 Aug 2022 10:14:55 -0700 (PDT) Received: from gmail.com (84-236-113-167.pool.digikabel.hu. [84.236.113.167]) by smtp.gmail.com with ESMTPSA id u11-20020a05600c19cb00b003a302fb9df7sm3438954wmq.21.2022.08.03.10.14.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 03 Aug 2022 10:14:54 -0700 (PDT) Sender: Ingo Molnar Date: Wed, 3 Aug 2022 19:14:52 +0200 From: Ingo Molnar To: "Paul E. McKenney" Cc: Steven Rostedt , Liu Song , mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, vschneid@redhat.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH] sched/debug: avoid executing show_state and causing rcu stall warning Message-ID: References: <1659489525-82994-1-git-send-email-liusong@linux.alibaba.com> <20220803084235.5d56d1e4@gandalf.local.home> <20220803140653.GD2125313@paulmck-ThinkPad-P17-Gen-1> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220803140653.GD2125313@paulmck-ThinkPad-P17-Gen-1> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Paul E. McKenney wrote: > There is an rcu_sysrq_start() and rcu_sysrq_end() to suppress this. > These are invoked by __handle_sysrq(). The value of > rcu_cpu_stall_suppress should be non-zero during the sysrq execution, and > this should prevent RCU CPU stall warnings from being printed. > > That said, the code currently does not support overlapping calls to the > various functions that suppress RCU CPU stall warnings. Except that the > only other use in current mainline is rcu_panic(), which never > unsuppresses. > > So could you please check the value of rcu_cpu_stall_suppress? Just in > case some other form of suppression was added somewhere that I missed? So instead of supressing the (justified!) RCU stall messages, I'd much rather we apply only the minimal locking necessary for this debug printout. That should also solve the stall warnings as a side effect. Thanks, Ingo