From nobody Sun Jun 28 00:09:00 2026 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C45F7C433EF for ; Thu, 17 Feb 2022 15:26:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242447AbiBQP0O (ORCPT ); Thu, 17 Feb 2022 10:26:14 -0500 Received: from mxb-00190b01.gslb.pphosted.com ([23.128.96.19]:57354 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239847AbiBQP0N (ORCPT ); Thu, 17 Feb 2022 10:26:13 -0500 Received: from mail-ed1-x529.google.com (mail-ed1-x529.google.com [IPv6:2a00:1450:4864:20::529]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5F4CD2B1033; Thu, 17 Feb 2022 07:25:58 -0800 (PST) Received: by mail-ed1-x529.google.com with SMTP id q17so10327403edd.4; Thu, 17 Feb 2022 07:25:58 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=from:to:cc:subject:date:message-id; bh=bSgOxeSJt8cnP/CvpA9EZuXcjXeTNEZw5hWUR2FJOtw=; b=knv+NhjnXGyBJIi09/apBOogAjT2DKC0QydwlHLDILQomKWlu94vMKxxbb4AMcvCA3 t6IXryVR67bURYkM+ftwM//3YFuYG34J70iuB6oVRF0nqFpyhqcr0cLBSWW/uCAG3lOH raVlS1+7ZAdOC8M6kZVvbHk454OUnX8dxBSX7kxRJ5OBJVxGlUGw2zXiHEvEmMLvp8+c SlBYcEkXC751fDkwgp7a69dsPc+Gu5JCbHb3nx8BHJ6/xkZqhaKQf9GjJfIUr/f/Xg84 Y9d/YSKH9HXndyP++Sm82w2yaOtuyN3cUWW/24F4laqiC8htRkKSWqqTv8EqVGuMiZDW ngNg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id; bh=bSgOxeSJt8cnP/CvpA9EZuXcjXeTNEZw5hWUR2FJOtw=; b=pdmBaGSXllmtB7N7uzc4Ml+addKXNtFY9Wl1ZhYZTQVZYVcmvk98pglygeNoCpCY2t rixBJSP0uheQTlsVI7pabstEWcJ2YD/RYhDWeCYywYQ1pZp0mrAi65XlJwWDYOuxossg coxvTaXWp5zgSLpDN5f3uzMtLkOgImoQEY8v6TcMB5ol6LAO2pXE2v0b9idmhALKhV2k ZcVjy1FA3M9vbIDssMl8lAVKU4v11UIyabC1nnxUKHYAIfMtYA3xMmU+BhpX7CvfnQPR /4xe5WfL2aqb67uOgNxcVUJLPkgl/mDGy3awGOOfxxCjGneXG/wlEg7wFo5Y62dDlqnJ 9riA== X-Gm-Message-State: AOAM530pFgHj8V2He7yOuBrsS0x7vzDoRyHdkUwKMBBZ10cDKPfFXSYk PTieWybzSfEhj+tzoIV2lPPMWqu/bmZ3bsC0flk= X-Google-Smtp-Source: ABdhPJyDg2YG+jgpUvKAM5eSQ1s/iyvGB+fIFJzwD9Wcn8vEx9tLJxQsdJwflK0kfQwFUnkehPJuLA== X-Received: by 2002:aa7:cc02:0:b0:411:487e:36fe with SMTP id q2-20020aa7cc02000000b00411487e36femr3156305edt.338.1645111556805; Thu, 17 Feb 2022 07:25:56 -0800 (PST) Received: from localhost.localdomain ([62.96.250.75]) by smtp.gmail.com with ESMTPSA id u23sm928964edo.64.2022.02.17.07.25.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 17 Feb 2022 07:25:56 -0800 (PST) From: Padmanabha Srinivasaiah To: paulmck@kernel.org, josh@joshtriplett.org, rostedt@goodmis.org, mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com, joel@joelfernandes.org, rcu@vger.kernel.org, linux-kernel@vger.kernel.org Cc: tj@kernel.org, treasure4paddy@gmail.com, linux-rpi-kernel@lists.infradead.org, linux-arm-kernel@lists.infradead.org Subject: [PATCH] rcu-tasks: Fix race in schedule and flush work Date: Thu, 17 Feb 2022 16:25:19 +0100 Message-Id: <20220217152520.18972-1-treasure4paddy@gmail.com> X-Mailer: git-send-email 2.17.1 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" While booting secondary CPUs, cpus_read_[lock/unlock] not keeping online cpumask stable. The transient online mask results in below calltrace. [ 0.324121] CPU1: Booted secondary processor 0x0000000001 [0x410fd083] [ 0.346652] Detected PIPT I-cache on CPU2 [ 0.347212] CPU2: Booted secondary processor 0x0000000002 [0x410fd083] [ 0.377255] Detected PIPT I-cache on CPU3 [ 0.377823] CPU3: Booted secondary processor 0x0000000003 [0x410fd083] [ 0.379040] ------------[ cut here ]------------ [ 0.383662] WARNING: CPU: 0 PID: 10 at kernel/workqueue.c:3084 __flush_w= ork+0x12c/0x138 [ 0.384850] Modules linked in: [ 0.385403] CPU: 0 PID: 10 Comm: rcu_tasks_rude_ Not tainted 5.17.0-rc3-= v8+ #13 [ 0.386473] Hardware name: Raspberry Pi 4 Model B Rev 1.4 (DT) [ 0.387289] pstate: 20000005 (nzCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE= =3D--) [ 0.388308] pc : __flush_work+0x12c/0x138 [ 0.388970] lr : __flush_work+0x80/0x138 [ 0.389620] sp : ffffffc00aaf3c60 [ 0.390139] x29: ffffffc00aaf3d20 x28: ffffffc009c16af0 x27: ffffff80f76= 1df48 [ 0.391316] x26: 0000000000000004 x25: 0000000000000003 x24: 00000000000= 00100 [ 0.392493] x23: ffffffffffffffff x22: ffffffc009c16b10 x21: ffffffc009c= 16b28 [ 0.393668] x20: ffffffc009e53861 x19: ffffff80f77fbf40 x18: 00000000d74= 4fcc9 [ 0.394842] x17: 000000000000000b x16: 00000000000001c2 x15: ffffffc009e= 57550 [ 0.396016] x14: 0000000000000000 x13: ffffffffffffffff x12: 00000001000= 00000 [ 0.397190] x11: 0000000000000462 x10: ffffff8040258008 x9 : 00000001000= 00000 [ 0.398364] x8 : 0000000000000000 x7 : ffffffc0093c8bf4 x6 : 00000000000= 00000 [ 0.399538] x5 : 0000000000000000 x4 : ffffffc00a976e40 x3 : ffffffc0081= 0444c [ 0.400711] x2 : 0000000000000004 x1 : 0000000000000000 x0 : 00000000000= 00000 [ 0.401886] Call trace: [ 0.402309] __flush_work+0x12c/0x138 [ 0.402941] schedule_on_each_cpu+0x228/0x278 [ 0.403693] rcu_tasks_rude_wait_gp+0x130/0x144 [ 0.404502] rcu_tasks_kthread+0x220/0x254 [ 0.405264] kthread+0x174/0x1ac [ 0.405837] ret_from_fork+0x10/0x20 [ 0.406456] irq event stamp: 102 [ 0.406966] hardirqs last enabled at (101): [] _raw_s= pin_unlock_irq+0x78/0xb4 [ 0.408304] hardirqs last disabled at (102): [] el1_db= g+0x24/0x5c [ 0.409410] softirqs last enabled at (54): [] local_b= h_enable+0xc/0x2c [ 0.410645] softirqs last disabled at (50): [] local_b= h_disable+0xc/0x2c [ 0.411890] ---[ end trace 0000000000000000 ]--- [ 0.413000] smp: Brought up 1 node, 4 CPUs [ 0.413762] SMP: Total of 4 processors activated. [ 0.414566] CPU features: detected: 32-bit EL0 Support [ 0.415414] CPU features: detected: 32-bit EL1 Support [ 0.416278] CPU features: detected: CRC32 instructions [ 0.447021] Callback from call_rcu_tasks_rude() invoked. [ 0.506693] Callback from call_rcu_tasks() invoked. Link: https://lore.kernel.org/lkml/20220210184319.25009-1-treasure4paddy@gm= ail.com/T/ Suggested-by: Paul E. McKenney Signed-off-by: Padmanabha Srinivasaiah Tested-by: Padmanabha Srinivasaiah --- kernel/rcu/tasks.h | 3 +++ 1 file changed, 3 insertions(+) diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h index d64f0b1d8cd3..30c42797f53b 100644 --- a/kernel/rcu/tasks.h +++ b/kernel/rcu/tasks.h @@ -950,6 +950,9 @@ static void rcu_tasks_be_rude(struct work_struct *work) // Wait for one rude RCU-tasks grace period. static void rcu_tasks_rude_wait_gp(struct rcu_tasks *rtp) { + if (num_online_cpus() <=3D 1) + return; // Fastpath for only one CPU. + rtp->n_ipis +=3D cpumask_weight(cpu_online_mask); schedule_on_each_cpu(rcu_tasks_be_rude); } --=20 2.17.1