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 71792C433EF for ; Wed, 10 Nov 2021 19:50:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5C26A6113E for ; Wed, 10 Nov 2021 19:50:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232146AbhKJTxZ (ORCPT ); Wed, 10 Nov 2021 14:53:25 -0500 Received: from mail-pj1-f43.google.com ([209.85.216.43]:40684 "EHLO mail-pj1-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231944AbhKJTxW (ORCPT ); Wed, 10 Nov 2021 14:53:22 -0500 Received: by mail-pj1-f43.google.com with SMTP id gf14-20020a17090ac7ce00b001a7a2a0b5c3so2562201pjb.5 for ; Wed, 10 Nov 2021 11:50:35 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=Mo5YZKmHyRzCkm81yC0SP0wa5RXfdbdNjSOonoGLKIQ=; b=iPlvH7gkM6vL/x5YYeCJLXPguV2wcAIAEkwSsz3SQokgyjO/1607TlnoSHHNtGXYP3 w+xt6jpFHustjMqmS3pvTevoigaY5Lx+9ffy+q+W1Gp3w8Z8WalX36t8zFJ/H0vKTsCG nLAyTpwjeawr7V0O+cpCelRNSOzJ2jbKdf67Arxo5gCA/YeMSa3UrCqp0aDrTwBUJWTG 9qjMP/ymVb9RYbPDSSkdhzFMPXhR2p/qNP3mx/+jMoRM5UvmekHkYZwpnhmSIT0kS5KW RbxJd0GxDB/ciN/U5v2nNYkfMZjA5/JqxZLCUoYLySl88jTtkrng2+SsWKNqJrP/EsOj ln2A== X-Gm-Message-State: AOAM533IIcbUHkmHhE7GpS5batG8xSKwsofbQTYvYKQNoqrmhTmVCXsj /z8pkbD8FbvhQElSusxvKy8= X-Google-Smtp-Source: ABdhPJya2DgM3aSAJccMby5bM3ok2fVFwWCNM7NUIHMJrIAqOTjmGRXJZ72if4N5reehWnZR92vzSA== X-Received: by 2002:a17:903:2344:b0:142:25b4:76c1 with SMTP id c4-20020a170903234400b0014225b476c1mr1798630plh.43.1636573834724; Wed, 10 Nov 2021 11:50:34 -0800 (PST) Received: from sultan-box.localdomain ([199.116.118.235]) by smtp.gmail.com with ESMTPSA id ml24sm402251pjb.16.2021.11.10.11.50.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 10 Nov 2021 11:50:34 -0800 (PST) Date: Wed, 10 Nov 2021 11:50:30 -0800 From: Sultan Alsawaf To: Vincent Guittot Cc: Peter Zijlstra , 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 , mkoutny@suse.com Subject: Re: printk deadlock due to double lock attempt on current CPU's runqueue Message-ID: 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: 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") I should clarify that I didn't actually reproduce the issue on v5.15; I just saw that the call chain leading to the deadlock still existed in v5.15 after looking through the code. Failing the SCHED_WARN_ON(rq->tmp_alone_branch != &rq->leaf_cfs_rq_list); assert is extremely rare in my experience, and I don't have a reproducer. It has only happened once after months of heavy usage (with lots of reboots too, so not with crazy high uptime). Sultan