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=-12.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 689A8C433E0 for ; Mon, 15 Mar 2021 23:12:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3252D64F64 for ; Mon, 15 Mar 2021 23:12:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229867AbhCOXLa (ORCPT ); Mon, 15 Mar 2021 19:11:30 -0400 Received: from mail.kernel.org ([198.145.29.99]:47936 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233397AbhCOXLS (ORCPT ); Mon, 15 Mar 2021 19:11:18 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 06BF364E07; Mon, 15 Mar 2021 23:11:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1615849878; bh=cyt5+m+H54MVA06BZt1j4xvZoJYimo2TbsujhwdmfqY=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=vBsskRe2rS+ejZ+ePVYbUtBliABoidDpSi6G1pcG5gTi4XUX25/C3YC8KV0CbGfEN VUEv/i4iJzDjflOXFzPaXtSPZVy+U6O53VrQI5JSNuEN8+zjOeR5u3Wz8nFBYSzicY LC3Pfj45R4SPIsVs3jZdw84fQpL1M9bQNvyE/D9kAKfUEHVBMiEjQB4PuPLNgEc0SN wh/E1qYUZdhCp+nXCsptsEG29dTJ0OlUSoUsqxWJDO0M+8UTvxOk3vC8evkphEIkUc dpzc/Z3iEElfeZ9qgEY/rTFZmo48JZFEj9SRJGzhYQPC+1gl9tAkmbxpBB1DcoL1iW PlWqOernvxXDg== Received: by paulmck-ThinkPad-P72.home (Postfix, from userid 1000) id C315235239EE; Mon, 15 Mar 2021 16:11:17 -0700 (PDT) Date: Mon, 15 Mar 2021 16:11:17 -0700 From: "Paul E. McKenney" To: Frederic Weisbecker Cc: rcu@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com, mingo@kernel.org, jiangshanlai@gmail.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org Subject: Re: [PATCH tip/core/rcu 06/10] softirq: Don't try waking ksoftirqd before it has been spawned Message-ID: <20210315231117.GP2696@paulmck-ThinkPad-P72> Reply-To: paulmck@kernel.org References: <20210303235958.GA22373@paulmck-ThinkPad-P72> <20210304000019.22459-6-paulmck@kernel.org> <20210312113641.GA3646@lothringen> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210312113641.GA3646@lothringen> User-Agent: Mutt/1.9.4 (2018-02-28) Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org On Fri, Mar 12, 2021 at 12:36:41PM +0100, Frederic Weisbecker wrote: > On Wed, Mar 03, 2021 at 04:00:15PM -0800, paulmck@kernel.org wrote: > > From: "Paul E. McKenney" > > > > If there is heavy softirq activity, the softirq system will attempt > > to awaken ksoftirqd and will stop the traditional back-of-interrupt > > softirq processing. This is all well and good, but only if the > > ksoftirqd kthreads already exist, which is not the case during early > > boot, in which case the system hangs. > > > > One reproducer is as follows: > > > > tools/testing/selftests/rcutorture/bin/kvm.sh --allcpus --duration 2 --configs "TREE03" --kconfig "CONFIG_DEBUG_LOCK_ALLOC=y CONFIG_PROVE_LOCKING=y CONFIG_NO_HZ_IDLE=y CONFIG_HZ_PERIODIC=n" --bootargs "threadirqs=1" --trust-make > > > > This commit therefore adds a couple of existence checks for ksoftirqd > > and forces back-of-interrupt softirq processing when ksoftirqd does not > > yet exist. With this change, the above test passes. > > > > Reported-by: Sebastian Andrzej Siewior > > Reported-by: Uladzislau Rezki > > Cc: Peter Zijlstra > > Cc: Thomas Gleixner > > [ paulmck: Remove unneeded check per Sebastian Siewior feedback. ] > > Signed-off-by: Paul E. McKenney > > Reviewed-by: Frederic Weisbecker Applied, thank you! Thanx, Paul