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=-9.8 required=3.0 tests=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,USER_AGENT_GIT 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 B3176C433E0 for ; Wed, 20 May 2020 22:48:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8E52120873 for ; Wed, 20 May 2020 22:48:28 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=joelfernandes.org header.i=@joelfernandes.org header.b="HMo1TGmo" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728651AbgETWs2 (ORCPT ); Wed, 20 May 2020 18:48:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49822 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728424AbgETWs0 (ORCPT ); Wed, 20 May 2020 18:48:26 -0400 Received: from mail-qv1-xf41.google.com (mail-qv1-xf41.google.com [IPv6:2607:f8b0:4864:20::f41]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AF07BC061A0E for ; Wed, 20 May 2020 15:48:26 -0700 (PDT) Received: by mail-qv1-xf41.google.com with SMTP id er16so2230599qvb.0 for ; Wed, 20 May 2020 15:48:26 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=joelfernandes.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=RStaSzm0BE79LxWHy0r6BH6gCPvj9qWnIh+kjRrtDqs=; b=HMo1TGmoIadolO348/feUnNKreceXmNKSpkmSSZBAfVlijoSVb7QdgroRmplfbn43Q fRlJiTkyVCaEUr2sZuc7m3WQVaJC6ui1ntFR0I5Os/tIeou8a10HOEjN4v6OW0QjFezt VZyINWgAw8VPK+6riAK0tl6vVs4lAnSmPjXr8= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=RStaSzm0BE79LxWHy0r6BH6gCPvj9qWnIh+kjRrtDqs=; b=o6ma8TYdqyFt6Kf79sufuYGp1RCYojrM+bu2aO3Qydwrx4F0LQXhX1Ts52mCp1O4bo d+s30TA4XrCdonV7wfMNNO8NlljPeTlAZKuMaQYc0RsFeUXS9jFTZTqssBhACzjFb9wQ Talt7bE6TUbc8cbD9QXb0rLSK+83V/XPdeL8LyNdeEze4A/11rithtqT33ociLcuZKWb qN7P1+bipr4N+ZPgVozoBxT/X2v/INZMsnck+NkSpEul6WNWNjeARXlQfzaoHXm9xBRf 8cILjx9be+xGcYf5dODCGex3He8v8iG4BsmFtXlyn6R9OUCDZ2/tlrWU0Zow1iACqBcE pqNQ== X-Gm-Message-State: AOAM530twvJ98I6WkOaL1aCzTwNW+weR0bwwE96dNUupFdGgDBQaSTNN D3HbHb4zZmtzj9X3Hn/j7A3MRg== X-Google-Smtp-Source: ABdhPJx6kwE258pbhfEt1te9GYfBlCarhExCr10+mjpGezARIkHTrNcpY3adcrfm7+5RiLYQTARiKg== X-Received: by 2002:a0c:b78a:: with SMTP id l10mr7528048qve.121.1590014905916; Wed, 20 May 2020 15:48:25 -0700 (PDT) Received: from joelaf.cam.corp.google.com ([2620:15c:6:12:9c46:e0da:efbf:69cc]) by smtp.gmail.com with ESMTPSA id c3sm3451258qtp.24.2020.05.20.15.48.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 20 May 2020 15:48:25 -0700 (PDT) From: "Joel Fernandes (Google)" To: Nishanth Aravamudan , Julien Desfossez , Peter Zijlstra , Tim Chen , mingo@kernel.org, tglx@linutronix.de, pjt@google.com, torvalds@linux-foundation.org Cc: vpillai , linux-kernel@vger.kernel.org, fweisbec@gmail.com, keescook@chromium.org, kerrnel@google.com, Phil Auld , Aaron Lu , Aubrey Li , aubrey.li@linux.intel.com, Valentin Schneider , Mel Gorman , Pawan Gupta , Paolo Bonzini , Joel Fernandes , joel@joelfernandes.org, paulmck@kernel.org Subject: [PATCH RFC] sched: Use sched-RCU in core-scheduling balancing logic Date: Wed, 20 May 2020 18:48:18 -0400 Message-Id: <20200520224818.78930-1-joel@joelfernandes.org> X-Mailer: git-send-email 2.26.2.761.g0e0b3e54be-goog In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org rcu_read_unlock() can incur an infrequent deadlock in sched_core_balance(). Fix this by using sched-RCU instead. This fixes the following spinlock recursion observed when testing the core scheduling patches on PREEMPT=y kernel on ChromeOS: [ 3.240891] BUG: spinlock recursion on CPU#2, swapper/2/0 [ 3.240900] lock: 0xffff9cd1eeb28e40, .magic: dead4ead, .owner: swapper/2/0, .owner_cpu: 2 [ 3.240905] CPU: 2 PID: 0 Comm: swapper/2 Not tainted 5.4.22htcore #4 [ 3.240908] Hardware name: Google Eve/Eve, BIOS Google_Eve.9584.174.0 05/29/2018 [ 3.240910] Call Trace: [ 3.240919] dump_stack+0x97/0xdb [ 3.240924] ? spin_bug+0xa4/0xb1 [ 3.240927] do_raw_spin_lock+0x79/0x98 [ 3.240931] try_to_wake_up+0x367/0x61b [ 3.240935] rcu_read_unlock_special+0xde/0x169 [ 3.240938] ? sched_core_balance+0xd9/0x11e [ 3.240941] __rcu_read_unlock+0x48/0x4a [ 3.240945] __balance_callback+0x50/0xa1 [ 3.240949] __schedule+0x55a/0x61e [ 3.240952] schedule_idle+0x21/0x2d [ 3.240956] do_idle+0x1d5/0x1f8 [ 3.240960] cpu_startup_entry+0x1d/0x1f [ 3.240964] start_secondary+0x159/0x174 [ 3.240967] secondary_startup_64+0xa4/0xb0 [ 14.998590] watchdog: BUG: soft lockup - CPU#0 stuck for 11s! [kworker/0:10:965] Cc: vpillai Cc: Aaron Lu Cc: Aubrey Li Cc: peterz@infradead.org Cc: paulmck@kernel.org Signed-off-by: Joel Fernandes (Google) Change-Id: I1a4bf0cd1426b3c21ad5de44719813ad4ee5805e --- kernel/sched/core.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 780514d03da47..b8ca6fcaaaf06 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -4897,7 +4897,7 @@ static void sched_core_balance(struct rq *rq) struct sched_domain *sd; int cpu = cpu_of(rq); - rcu_read_lock(); + rcu_read_lock_sched(); raw_spin_unlock_irq(rq_lockp(rq)); for_each_domain(cpu, sd) { if (!(sd->flags & SD_LOAD_BALANCE)) @@ -4910,7 +4910,7 @@ static void sched_core_balance(struct rq *rq) break; } raw_spin_lock_irq(rq_lockp(rq)); - rcu_read_unlock(); + rcu_read_unlock_sched(); } static DEFINE_PER_CPU(struct callback_head, core_balance_head); -- 2.26.2.761.g0e0b3e54be-goog