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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 678FCC433EF for ; Thu, 14 Jul 2022 01:31:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232096AbiGNBbx (ORCPT ); Wed, 13 Jul 2022 21:31:53 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33930 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229990AbiGNBbr (ORCPT ); Wed, 13 Jul 2022 21:31:47 -0400 Received: from mail-pj1-x102f.google.com (mail-pj1-x102f.google.com [IPv6:2607:f8b0:4864:20::102f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3FF9F14D30; Wed, 13 Jul 2022 18:31:47 -0700 (PDT) Received: by mail-pj1-x102f.google.com with SMTP id o15so978798pjh.1; Wed, 13 Jul 2022 18:31:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=ilqttwPjepFmD0kTfN75XWGy4SipmcKZuxYQ1eii/xY=; b=GKRliKCwtnaD66A0Ae+OyYbPImmQaG2tNrTZKV1gZ52F3r1bLvcAc3Hr4mw3TrnmLD 9gQViN1fPPKUqykFkbr5g84/3mclhW118fP8W9N3SDEakHX8XD0ccUOjfFzMPCcJ2e/Q CD8wWNELZvy37nwwMaUw7ShL16oSQARG6pHoWktW9MtbDvy6XHPHzqXxFmurZ3Slqz5G 4IZn3OoVCmF9me5jujxBy6bzz41aA/BFGIkmwEatV76QLX1dbWWHpSOippyHaisKom0U xBezwhqpglnHNTor5kRqsZMg7q18+Qpq1wNmnQZ7rkZICTNRp48kliBXk6OWtxYpKFvz 41pg== 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:mime-version :content-transfer-encoding; bh=ilqttwPjepFmD0kTfN75XWGy4SipmcKZuxYQ1eii/xY=; b=NKd7/wPWeHKibpmN1j7nO0seENEAPGcmoTYCGLMkb27eREURBKpsInf2PJjOjjTy81 AzWm5/bBBmlHRxh4vr5L2u78TIyBR4DTcZzt9uFuYxrThZNz18XV/nR2bfoRZ7KHCVUg tXRcalQXgPCUBuuqPlgNmmYy9yRqVfSJZ9Lb/lad4XWIWF7wCcdjFTbMG+/3cu3WcgZA N6AVUXm7H5z9vMJjoLqt281xIwesTLVxAbASmHnF2RaR4g6EXR8xZ6aAGAGWJyYcAZZk hs/3VayELe1paDsXD5Cqn7WcSjRuNWT/NTtVIzpyIcSnfaRhVJ+aWK4/uBHpBMD4HlQN fWxQ== X-Gm-Message-State: AJIora+8Ct30as3E03JYIEO0jGIoqAcpR/V6jDsgZPM0P3Onivay4/jY yWQU5GBSGr90tzd2ZTaLp0I= X-Google-Smtp-Source: AGRyM1veZQifNlI6HlJ1G5RFvwADsMIqAt4I7Ix+cZ73sqMaCWOau4H+HR4whROaPJKbCpwYRJGREw== X-Received: by 2002:a17:90a:2c0d:b0:1ef:c839:c34b with SMTP id m13-20020a17090a2c0d00b001efc839c34bmr13481892pjd.39.1657762306790; Wed, 13 Jul 2022 18:31:46 -0700 (PDT) Received: from localhost.localdomain ([85.203.23.27]) by smtp.gmail.com with ESMTPSA id r14-20020a63ec4e000000b004150a28a56fsm21912pgj.53.2022.07.13.18.31.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 13 Jul 2022 18:31:46 -0700 (PDT) From: Zhouyi Zhou To: mpe@ellerman.id.au, benh@kernel.crashing.org, paulus@samba.org, npiggin@gmail.com, ldufour@linux.ibm.com, pmladek@suse.com, john.ogness@linutronix.de, Julia.Lawall@inria.fr, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, lance@osuosl.org, paulmck@kernel.org, rcu@vger.kernel.org Cc: Zhouyi Zhou Subject: [PATCH linux-next] powerpc: use raw_smp_processor_id in arch_touch_nmi_watchdog Date: Thu, 14 Jul 2022 09:31:31 +0800 Message-Id: <20220714013131.12648-1-zhouzhouyi@gmail.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org use raw_smp_processor_id() in arch_touch_nmi_watchdog because when called from watchdog, the cpu is preemptible. Signed-off-by: Zhouyi Zhou --- Dear PPC developers I found this bug when trying to do rcutorture tests in ppc VM of Open Source Lab of Oregon State University. qemu-system-ppc64 -nographic -smp cores=4,threads=1 -net none -M pseries -nodefaults -device spapr-vscsi -serial file:/tmp/console.log -m 2G -kernel /home/ubuntu/linux-next/tools/testing/selftests/rcutorture/res/2022.07.08-22.36.11-torture/results-rcuscale-kvfree/TREE/vmlinux -append "debug_boot_weak_hash panic=-1 console=ttyS0 rcuscale.kfree_rcu_test=1 rcuscale.kfree_nthreads=16 rcuscale.holdoff=20 rcuscale.kfree_loops=10000 torture.disable_onoff_at_boot rcuscale.shutdown=1 rcuscale.verbose=0" tail /tmp/console.log [ 1232.433552][ T41] BUG: using smp_processor_id() in preemptible [00000000] code: khungtaskd/41 [ 1232.439751][ T41] caller is arch_touch_nmi_watchdog+0x34/0xd0 [ 1232.440934][ T41] CPU: 3 PID: 41 Comm: khungtaskd Not tainted 5.19.0-rc5-next-20220708-dirty #106 [ 1232.442684][ T41] Call Trace: [ 1232.443343][ T41] [c0000000029cbbb0] [c0000000006df360] dump_stack_lvl+0x74/0xa8 (unreliable) [ 1232.445237][ T41] [c0000000029cbbf0] [c000000000d04f30] check_preemption_disabled+0x150/0x160 [ 1232.446926][ T41] [c0000000029cbc80] [c000000000035584] arch_touch_nmi_watchdog+0x34/0xd0 [ 1232.448532][ T41] [c0000000029cbcb0] [c0000000002068ac] watchdog+0x40c/0x5b0 [ 1232.451449][ T41] [c0000000029cbdc0] [c000000000139df4] kthread+0x144/0x170 [ 1232.452896][ T41] [c0000000029cbe10] [c00000000000cd54] ret_from_kernel_thread+0x5c/0x64 After this fix, "BUG: using smp_processor_id() in preemptible [00000000] code: khungtaskd/41" does not appear again. I also examined other places in watchdog.c where smp_processor_id() are used, but they are well protected by preempt disable. Kind Regards Zhouyi -- arch/powerpc/kernel/watchdog.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/powerpc/kernel/watchdog.c b/arch/powerpc/kernel/watchdog.c index 7d28b9553654..ab6b84e00311 100644 --- a/arch/powerpc/kernel/watchdog.c +++ b/arch/powerpc/kernel/watchdog.c @@ -450,7 +450,7 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer) void arch_touch_nmi_watchdog(void) { unsigned long ticks = tb_ticks_per_usec * wd_timer_period_ms * 1000; - int cpu = smp_processor_id(); + int cpu = raw_smp_processor_id(); u64 tb; if (!cpumask_test_cpu(cpu, &watchdog_cpumask)) -- 2.25.1