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=-7.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, SPF_HELO_NONE,SPF_PASS autolearn=no 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 9932CC4320E for ; Tue, 31 Aug 2021 17:12:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7DC116109E for ; Tue, 31 Aug 2021 17:12:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238832AbhHaRNL (ORCPT ); Tue, 31 Aug 2021 13:13:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47372 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229602AbhHaRNK (ORCPT ); Tue, 31 Aug 2021 13:13:10 -0400 Received: from mail-ed1-x532.google.com (mail-ed1-x532.google.com [IPv6:2a00:1450:4864:20::532]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 49F4AC061575 for ; Tue, 31 Aug 2021 10:12:15 -0700 (PDT) Received: by mail-ed1-x532.google.com with SMTP id u19so11230126edb.3 for ; Tue, 31 Aug 2021 10:12:15 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=ZbHfXvVhh4iun/ZRNpYXmFxLkzcbeoToQ9hWGOmo5g4=; b=SlgmD1ij7i7ApMQIQnKt+oOIsZZimChZMMREL2RjDMOQeorqxFNgv5Rt42zIMg9imj 9F+xu1dMp/14lQ/u2iuCRIboetcCjLV2NGcyw70Xy/3k2c+L/mmvRhainUbtolfAc1ZQ MhdC1Wl9oDnUaMcgseUbF2snLbMgvA/+xjwjLZIVWR3dQ1AxlLCstD8PZpLLA+U9DICR KarL2dtMUiPRSBE1aQ1ZUPffzltOVRe56equE8xKTJRxtICz9ZR3ABIk6wZpWLQzyudN OjGmSZTS3DK47zgZDNn7e3b+2mDRdZteuTVJ9I5gmrJAxly//ZiXFGg/Tcd6gaIv2cDn Ze2A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=ZbHfXvVhh4iun/ZRNpYXmFxLkzcbeoToQ9hWGOmo5g4=; b=s8elgD9Il5UpikA/cY783SpwQj14K65/4VSg/xCSeyaMfP4JJilEpQ9rIuFiCf+IkL Vv5gkCnhze7Y8gW0ug8ayHkKq4i3PhoC1xtxvguzG4S0LSPpgiKQhuzk+ZibzW4MYTV7 zKZS8SmA02bQsPtT/bpeopYzfUFD+h13SWElPX4tryG3GVShYzlxHj5Z/6Go5I/a4G9a A7jpuw39ONWdrbwjImm7dMH92UWdEkAcnsfh/0P0ZsS76Wv5dWPAL7Xif0t0nhosTpAl tJ94lTZQ1KU1Qn0a7KCN39iz9T4XN9ahHi6soJHr4TLogGuyXb9c3vBWTXnNast+yTEx tvxw== X-Gm-Message-State: AOAM533sKrEhwyJDOXhnHXO94wSv8ClmR6w81jWlmrgfFoF9POInC8d9 KoE2DvNpQ2z/978LX7uXr3Nwmo6vDNSRLBlydTI= X-Google-Smtp-Source: ABdhPJykAyAX75ZlSvAzih6ZHrougq8MBknQsYjWB5ZbxRRItoWAMaMQWvYbyCb6guNARJMVDBXxl1uHrjsAQF6A+EQ= X-Received: by 2002:aa7:d6d1:: with SMTP id x17mr31085378edr.64.1630429933895; Tue, 31 Aug 2021 10:12:13 -0700 (PDT) MIME-Version: 1.0 References: <20210831152144.GA28128@trex> In-Reply-To: From: Zhouyi Zhou Date: Wed, 1 Sep 2021 01:11:59 +0800 Message-ID: Subject: Re: rcu_preempt detected stalls To: "Jorge Ramirez-Ortiz, Foundries" List-Id: Cc: paulmck@kernel.org, Josh Triplett , rostedt , Mathieu Desnoyers , Lai Jiangshan , "Joel Fernandes, Google" , rcu , soc@kernel.org, linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org Message-ID: <20210831171159.Caiy93dta2elfXEUStSbVXz6SIVAGVd8q_RXZaHHxrA@z> followings are some of my kernel config options: CONFIG_PREEMPT=y CONFIG_PREEMPT_COUNT=y CONFIG_PREEMPTION=y CONFIG_PREEMPT_DYNAMIC=y CONFIG_PREEMPT_RCU=y CONFIG_HAVE_PREEMPT_DYNAMIC=y CONFIG_TREE_RCU=y CONFIG_PREEMPT_RCU=y CONFIG_RCU_EXPERT=y CONFIG_SRCU=y CONFIG_TREE_SRCU=y CONFIG_TASKS_RCU_GENERIC=y CONFIG_TASKS_RCU=y CONFIG_TASKS_RUDE_RCU=y CONFIG_TASKS_TRACE_RCU=y CONFIG_RCU_STALL_COMMON=y CONFIG_RCU_NEED_SEGCBLIST=y CONFIG_RCU_FANOUT=64 CONFIG_RCU_FANOUT_LEAF=16 # CONFIG_RCU_FAST_NO_HZ is not set # CONFIG_RCU_BOOST is not set CONFIG_RCU_NOCB_CPU=y # CONFIG_TASKS_TRACE_RCU_READ_MB is not set # end of RCU Subsystem CONFIG_MMU_GATHER_RCU_TABLE_FREE=y CONFIG_LOCKDEP_CIRCULAR_QUEUE_BITS=12 # RCU Debugging CONFIG_PROVE_RCU=y # CONFIG_PROVE_RCU_LIST is not set # CONFIG_RCU_SCALE_TEST is not set CONFIG_RCU_TORTURE_TEST=m # CONFIG_RCU_REF_SCALE_TEST is not set CONFIG_RCU_CPU_STALL_TIMEOUT=21 # CONFIG_RCU_TRACE is not set # CONFIG_RCU_EQS_DEBUG is not set Thanks Zhouyi On Wed, Sep 1, 2021 at 1:01 AM Zhouyi Zhou wrote: > > I did an experiment just now on x86_64 virtual machines, rcu did not > complain after 10 minutes's test, I hope my effort can provide some > clue. > > 1. I clone the fresh new linux kernel (git clone > https://kernel.source.codeaurora.cn/pub/scm/linux/kernel/git/torvalds/linux.git) > 2. compile the kernel without CONFIG_RCU_BOOST (: # CONFIG_RCU_BOOST is not set) > 3. boot the kernel on a x86_64 VM (kvm -cpu host -smp 16 -hda > ./debian10.qcow2 -m 4096 -net > user,hostfwd=tcp::5556-:22,hostfwd=tcp::5555-:19 -net nic,model=e1000 > -vnc :30) > 4. run the test (stress-ng --sequential 16 --class scheduler -t 5m --times) > 5. monitor the system by constantly typing top and dmesg > 6. after 10 minutes, nothing else happens except that the dmesg report > following two messages > [ 672.528192] sched: DL replenish lagged too much > [ 751.127790] hrtimer: interrupt took 12143 ns > > So, I guess CONFIG_RCU_BOOST is not necessary for x86_64 virtual machines > > Zhouyi > > On Tue, Aug 31, 2021 at 11:24 PM Jorge Ramirez-Ortiz, Foundries > wrote: > > > > Hi > > > > When enabling CONFIG_PREEMPT and running the stress-ng scheduler class > > tests on arm64 (xilinx zynqmp and imx imx8mm SoCs) we are observing the following. > > > > [ 62.578917] rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: > > [ 62.585015] (detected by 0, t=5253 jiffies, g=3017, q=2972) > > [ 62.590663] rcu: All QSes seen, last rcu_preempt kthread activity 5254 (4294907943-4294902689), jiffies_till_next_fqs=1, root > > +->qsmask 0x0 > > [ 62.603086] rcu: rcu_preempt kthread starved for 5258 jiffies! g3017 f0x2 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=1 > > [ 62.613246] rcu: Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior. > > [ 62.622359] rcu: RCU grace-period kthread stack dump: > > [ 62.627395] task:rcu_preempt state:R running task stack: 0 pid: 14 ppid: 2 flags:0x00000028 > > [ 62.637308] Call trace: > > [ 62.639748] __switch_to+0x11c/0x190 > > [ 62.643319] __schedule+0x3b8/0x8d8 > > [ 62.646796] schedule+0x4c/0x108 > > [ 62.650018] schedule_timeout+0x1ac/0x358 > > [ 62.654021] rcu_gp_kthread+0x6a8/0x12b8 > > [ 62.657933] kthread+0x14c/0x158 > > [ 62.661153] ret_from_fork+0x10/0x18 > > [ 62.682919] BUG: scheduling while atomic: stress-ng-hrtim/831/0x00000002 > > [ 62.689604] Preemption disabled at: > > [ 62.689614] [] irq_enter_rcu+0x30/0x58 > > [ 62.698393] CPU: 0 PID: 831 Comm: stress-ng-hrtim Not tainted 5.10.42+ #5 > > [ 62.706296] Hardware name: Zynqmp new (DT) > > [ 62.710115] Call trace: > > [ 62.712548] dump_backtrace+0x0/0x240 > > [ 62.716202] show_stack+0x2c/0x38 > > [ 62.719510] dump_stack+0xcc/0x104 > > [ 62.722904] __schedule_bug+0x78/0xc8 > > [ 62.726556] __schedule+0x70c/0x8d8 > > [ 62.730037] schedule+0x4c/0x108 > > [ 62.733259] do_notify_resume+0x224/0x5d8 > > [ 62.737259] work_pending+0xc/0x2a4 > > > > The error results in OOM eventually. > > > > RCU priority boosting does work around this issue but it seems to me > > a workaround more than a fix (otherwise boosting would be enabled > > by CONFIG_PREEMPT for arm64 I guess?). > > > > The question is: is this an arm64 bug that should be investigated? or > > is this some known corner case of running stress-ng that is already > > understood? > > > > thanks > > Jorge > > > > > > 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=-5.7 required=3.0 tests=BAYES_00,DKIM_ADSP_CUSTOM_MED, DKIM_SIGNED,DKIM_VALID,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, SPF_HELO_NONE,SPF_PASS autolearn=no 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 A7155C432BE for ; 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Tue, 31 Aug 2021 10:12:13 -0700 (PDT) MIME-Version: 1.0 References: <20210831152144.GA28128@trex> In-Reply-To: From: Zhouyi Zhou Date: Wed, 1 Sep 2021 01:11:59 +0800 Message-ID: Subject: Re: rcu_preempt detected stalls To: "Jorge Ramirez-Ortiz, Foundries" List-Id: Cc: paulmck@kernel.org, Josh Triplett , rostedt , Mathieu Desnoyers , Lai Jiangshan , "Joel Fernandes, Google" , rcu , soc@kernel.org, linux-arm-kernel@lists.infradead.org X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210831_101216_592888_A43E7EA9 X-CRM114-Status: GOOD ( 25.06 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Message-ID: <20210831171159.L6GWokiqRdP6iR7ifyRwmK4o4zLRDfv695oAA6v1sWc@z> followings are some of my kernel config options: CONFIG_PREEMPT=y CONFIG_PREEMPT_COUNT=y CONFIG_PREEMPTION=y CONFIG_PREEMPT_DYNAMIC=y CONFIG_PREEMPT_RCU=y CONFIG_HAVE_PREEMPT_DYNAMIC=y CONFIG_TREE_RCU=y CONFIG_PREEMPT_RCU=y CONFIG_RCU_EXPERT=y CONFIG_SRCU=y CONFIG_TREE_SRCU=y CONFIG_TASKS_RCU_GENERIC=y CONFIG_TASKS_RCU=y CONFIG_TASKS_RUDE_RCU=y CONFIG_TASKS_TRACE_RCU=y CONFIG_RCU_STALL_COMMON=y CONFIG_RCU_NEED_SEGCBLIST=y CONFIG_RCU_FANOUT=64 CONFIG_RCU_FANOUT_LEAF=16 # CONFIG_RCU_FAST_NO_HZ is not set # CONFIG_RCU_BOOST is not set CONFIG_RCU_NOCB_CPU=y # CONFIG_TASKS_TRACE_RCU_READ_MB is not set # end of RCU Subsystem CONFIG_MMU_GATHER_RCU_TABLE_FREE=y CONFIG_LOCKDEP_CIRCULAR_QUEUE_BITS=12 # RCU Debugging CONFIG_PROVE_RCU=y # CONFIG_PROVE_RCU_LIST is not set # CONFIG_RCU_SCALE_TEST is not set CONFIG_RCU_TORTURE_TEST=m # CONFIG_RCU_REF_SCALE_TEST is not set CONFIG_RCU_CPU_STALL_TIMEOUT=21 # CONFIG_RCU_TRACE is not set # CONFIG_RCU_EQS_DEBUG is not set Thanks Zhouyi On Wed, Sep 1, 2021 at 1:01 AM Zhouyi Zhou wrote: > > I did an experiment just now on x86_64 virtual machines, rcu did not > complain after 10 minutes's test, I hope my effort can provide some > clue. > > 1. I clone the fresh new linux kernel (git clone > https://kernel.source.codeaurora.cn/pub/scm/linux/kernel/git/torvalds/linux.git) > 2. compile the kernel without CONFIG_RCU_BOOST (: # CONFIG_RCU_BOOST is not set) > 3. boot the kernel on a x86_64 VM (kvm -cpu host -smp 16 -hda > ./debian10.qcow2 -m 4096 -net > user,hostfwd=tcp::5556-:22,hostfwd=tcp::5555-:19 -net nic,model=e1000 > -vnc :30) > 4. run the test (stress-ng --sequential 16 --class scheduler -t 5m --times) > 5. monitor the system by constantly typing top and dmesg > 6. after 10 minutes, nothing else happens except that the dmesg report > following two messages > [ 672.528192] sched: DL replenish lagged too much > [ 751.127790] hrtimer: interrupt took 12143 ns > > So, I guess CONFIG_RCU_BOOST is not necessary for x86_64 virtual machines > > Zhouyi > > On Tue, Aug 31, 2021 at 11:24 PM Jorge Ramirez-Ortiz, Foundries > wrote: > > > > Hi > > > > When enabling CONFIG_PREEMPT and running the stress-ng scheduler class > > tests on arm64 (xilinx zynqmp and imx imx8mm SoCs) we are observing the following. > > > > [ 62.578917] rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: > > [ 62.585015] (detected by 0, t=5253 jiffies, g=3017, q=2972) > > [ 62.590663] rcu: All QSes seen, last rcu_preempt kthread activity 5254 (4294907943-4294902689), jiffies_till_next_fqs=1, root > > +->qsmask 0x0 > > [ 62.603086] rcu: rcu_preempt kthread starved for 5258 jiffies! g3017 f0x2 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=1 > > [ 62.613246] rcu: Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior. > > [ 62.622359] rcu: RCU grace-period kthread stack dump: > > [ 62.627395] task:rcu_preempt state:R running task stack: 0 pid: 14 ppid: 2 flags:0x00000028 > > [ 62.637308] Call trace: > > [ 62.639748] __switch_to+0x11c/0x190 > > [ 62.643319] __schedule+0x3b8/0x8d8 > > [ 62.646796] schedule+0x4c/0x108 > > [ 62.650018] schedule_timeout+0x1ac/0x358 > > [ 62.654021] rcu_gp_kthread+0x6a8/0x12b8 > > [ 62.657933] kthread+0x14c/0x158 > > [ 62.661153] ret_from_fork+0x10/0x18 > > [ 62.682919] BUG: scheduling while atomic: stress-ng-hrtim/831/0x00000002 > > [ 62.689604] Preemption disabled at: > > [ 62.689614] [] irq_enter_rcu+0x30/0x58 > > [ 62.698393] CPU: 0 PID: 831 Comm: stress-ng-hrtim Not tainted 5.10.42+ #5 > > [ 62.706296] Hardware name: Zynqmp new (DT) > > [ 62.710115] Call trace: > > [ 62.712548] dump_backtrace+0x0/0x240 > > [ 62.716202] show_stack+0x2c/0x38 > > [ 62.719510] dump_stack+0xcc/0x104 > > [ 62.722904] __schedule_bug+0x78/0xc8 > > [ 62.726556] __schedule+0x70c/0x8d8 > > [ 62.730037] schedule+0x4c/0x108 > > [ 62.733259] do_notify_resume+0x224/0x5d8 > > [ 62.737259] work_pending+0xc/0x2a4 > > > > The error results in OOM eventually. > > > > RCU priority boosting does work around this issue but it seems to me > > a workaround more than a fix (otherwise boosting would be enabled > > by CONFIG_PREEMPT for arm64 I guess?). > > > > The question is: is this an arm64 bug that should be investigated? or > > is this some known corner case of running stress-ng that is already > > understood? > > > > thanks > > Jorge > > > > > > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel