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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DE9A9C433EF for ; Wed, 10 Nov 2021 10:45:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C273C611AD for ; Wed, 10 Nov 2021 10:45:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231229AbhKJKsB (ORCPT ); Wed, 10 Nov 2021 05:48:01 -0500 Received: from smtp-out2.suse.de ([195.135.220.29]:39196 "EHLO smtp-out2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229653AbhKJKsA (ORCPT ); Wed, 10 Nov 2021 05:48:00 -0500 Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id AE4A31FD3F; Wed, 10 Nov 2021 10:45:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1636541111; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=GUpTvZNhgXgXObp506QhXsYR81By+iDPFzAbaJOpy7E=; b=TnHZI7aCI7ViBAvgZ+UQC9O8UDlyQVUJBgV0QPZ0nOaVXq6ntU/j3fSteNuQoFjxEp4pqA sB7sLjxYQF6EqJg+SNCJbDVuQgSjEdwqUYMaWjVeLKGDZj1qhnwUo1wveJNtfIjldukL/C KQp3O7Wh6+WSEy66KMHjfi9VSa6x7u0= Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 6A92A13BEA; Wed, 10 Nov 2021 10:45:11 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id JyhlGbeii2GhQAAAMHmgww (envelope-from ); Wed, 10 Nov 2021 10:45:11 +0000 Date: Wed, 10 Nov 2021 11:45:10 +0100 From: Michal =?iso-8859-1?Q?Koutn=FD?= To: Vincent Guittot Cc: Peter Zijlstra , Sultan Alsawaf , Anton Vorontsov , Ben Segall , Colin Cross , Daniel Bristot de Oliveira , Daniel Vetter , David Airlie , Dietmar Eggemann , dri-devel@lists.freedesktop.org, Ingo Molnar , John Ogness , Juri Lelli , Kees Cook , linux-kernel@vger.kernel.org, Maarten Lankhorst , Maxime Ripard , Mel Gorman , Petr Mladek , Sergey Senozhatsky , Steven Rostedt , Thomas Zimmermann , Tony Luck Subject: Re: printk deadlock due to double lock attempt on current CPU's runqueue Message-ID: <20211110104510.GB20566@blackbody.suse.cz> References: <20211109213847.GY174703@worktop.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Nov 10, 2021 at 10:00:35AM +0100, Vincent Guittot wrote: > Is it the same SCHED_WARN_ON(rq->tmp_alone_branch != > &rq->leaf_cfs_rq_list); that generates the deadlock on v5.15 too ? > > one remaining tmp_alone_branch warning has been fixed in v5.15 with > 2630cde26711 ("sched/fair: Add ancestors of unthrottled undecayed cfs_rq") AFAIK, the warning is typically triggered on v5.13 when CPU throttling is employeed. The cfs_rq list is mis-ordered but it shouldn't be fatal. But the throttling currently (since v5.13 too) also exposes a race on task_group removal that can lead to corrupting the cfs_rq list (another thread [1], I'll leave this thread for printk (non)-locking). HTH, Michal [1] https://lore.kernel.org/r/20211011172236.11223-1-mkoutny@suse.com/