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=-9.9 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,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 09897C10DCE for ; Fri, 13 Mar 2020 23:29:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D081620658 for ; Fri, 13 Mar 2020 23:29:29 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=joelfernandes.org header.i=@joelfernandes.org header.b="vpaN+NIS" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727186AbgCMX32 (ORCPT ); Fri, 13 Mar 2020 19:29:28 -0400 Received: from mail-qv1-f66.google.com ([209.85.219.66]:44184 "EHLO mail-qv1-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726591AbgCMX32 (ORCPT ); Fri, 13 Mar 2020 19:29:28 -0400 Received: by mail-qv1-f66.google.com with SMTP id w5so5619654qvp.11 for ; Fri, 13 Mar 2020 16:29:27 -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:mime-version :content-transfer-encoding; bh=69w0IAqxf9mqjiQh6d+eU21vBcUH24Ogd6Z5EgYS968=; b=vpaN+NISRDEGC/3fS1vQcHRYNTL4vGCwS15Hgl8FWFc6Ey+vgruYdyK1G397WSjtFO /wgShAnlT0fhRpFyTcruxZXNAn3fLqLG8SQ/A/hIBsUKS54YDgxIRXVJVBNNsqkZIIXT ve9RBOYuJRonGCuGe/NVoTBrCHHVLn21KC0Ag= 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:mime-version :content-transfer-encoding; bh=69w0IAqxf9mqjiQh6d+eU21vBcUH24Ogd6Z5EgYS968=; b=OXwzshbklgttF4VKzcGKBwDfqgTx186N/snkf8ZODK0GZnk2+SVQpqjSlCVqjeEiqH Zqd10LdpDf2+kjE9JpquZxa8K1dHB/gNQL0qK7tYuOXCqlZcUC+vg07p6pjSB6gfx8fy tbWzaVh7CmAKkpW5wPxNzdbckKMq5FlsBLrd6XJuvb96oIZSzYTspb3pqE/djCiWEPnT QQMR33hg/UmKxQbi1w50vQ9Qv/ph9seBAT5mzEPxk2Gf2TB2kvxW6hwywWZ2k7txbyES N75FblciSdvg1I/gwiuLA/o0tStv87VR/qXRyAX1XVLFdxca9E+0ReQdz1jQFkQfUag1 yGjw== X-Gm-Message-State: ANhLgQ39SzCQsvrHbLRD5FMr0JPTFzeYfu2xHit88M5InBogwLyKIYcv qszFlrQt+oApfQyJTUzuXL6BuS+vwMA= X-Google-Smtp-Source: ADFU+vt5J5Ut4zQIOZV7bmd7wASp+G/ZaYwfScA2MWJpW94XAiNWPdq8ud62G5O2ql9Q76zhEZF4bg== X-Received: by 2002:a0c:ebcc:: with SMTP id k12mr13538558qvq.69.1584142167093; Fri, 13 Mar 2020 16:29:27 -0700 (PDT) Received: from joelaf.cam.corp.google.com ([2620:15c:6:12:9c46:e0da:efbf:69cc]) by smtp.gmail.com with ESMTPSA id x51sm10143593qtj.82.2020.03.13.16.29.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 13 Mar 2020 16:29:26 -0700 (PDT) From: "Joel Fernandes (Google)" To: linux-kernel@vger.kernel.org Cc: "Joel Fernandes (Google)" , vpillai , Aaron Lu , Aubrey Li , peterz@infradead.org, paulmck@kernel.org, Ben Segall , Dietmar Eggemann , Ingo Molnar , Juri Lelli , Mel Gorman , Steven Rostedt , Vincent Guittot Subject: [PATCH] sched: Use RCU-sched in core-scheduling balancing logic Date: Fri, 13 Mar 2020 19:29:18 -0400 Message-Id: <20200313232918.62303-1-joel@joelfernandes.org> X-Mailer: git-send-email 2.25.1.481.gfbce0eb801-goog 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 the RCU-sched flavor 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) --- 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 3045bd50e249..037e8f2e2686 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -4735,7 +4735,7 @@ 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)) @@ -4748,7 +4748,7 @@ 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); -- 2.25.1.481.gfbce0eb801-goog