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 521E1C6FD1D for ; Wed, 15 Mar 2023 09:57:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230324AbjCOJ5M (ORCPT ); Wed, 15 Mar 2023 05:57:12 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45660 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229727AbjCOJ4l (ORCPT ); Wed, 15 Mar 2023 05:56:41 -0400 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 583BA1632A for ; Wed, 15 Mar 2023 02:55:15 -0700 (PDT) Received: from canpemm500009.china.huawei.com (unknown [172.30.72.57]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4Pc5Mb6SrLzrSjh; Wed, 15 Mar 2023 17:54:19 +0800 (CST) Received: from [10.67.102.169] (10.67.102.169) by canpemm500009.china.huawei.com (7.192.105.203) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.21; Wed, 15 Mar 2023 17:55:13 +0800 CC: , , , , , , , , , , , , , , Subject: Re: [PATCH] sched/fair: Don't balance migration disabled tasks To: Chen Yu References: <20230313065759.39698-1-yangyicong@huawei.com> From: Yicong Yang Message-ID: Date: Wed, 15 Mar 2023 17:55:13 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.5.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.67.102.169] X-ClientProxiedBy: dggems704-chm.china.huawei.com (10.3.19.181) To canpemm500009.china.huawei.com (7.192.105.203) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2023/3/14 11:08, Chen Yu wrote: > On 2023-03-13 at 14:57:59 +0800, Yicong Yang wrote: >> From: Yicong Yang >> >> On load balance we didn't check whether the candidate task is migration >> disabled or not, this may hit the WARN_ON in set_task_cpu() since the >> migration disabled tasks are expected to run on their current CPU. >> We've run into this case several times on our server: >> >> ------------[ cut here ]------------ >> WARNING: CPU: 7 PID: 0 at kernel/sched/core.c:3115 set_task_cpu+0x188/0x240 >> Modules linked in: hclgevf xt_CHECKSUM ipt_REJECT nf_reject_ipv4 <...snip> >> CPU: 7 PID: 0 Comm: swapper/7 Kdump: loaded Tainted: G O 6.1.0-rc4+ #1 >> Hardware name: Huawei TaiShan 2280 V2/BC82AMDC, BIOS 2280-V2 CS V5.B221.01 12/09/2021 >> pstate: 604000c9 (nZCv daIF +PAN -UAO -TCO -DIT -SSBS BTYPE=--) >> pc : set_task_cpu+0x188/0x240 >> lr : load_balance+0x5d0/0xc60 >> sp : ffff80000803bc70 >> x29: ffff80000803bc70 x28: ffff004089e190e8 x27: ffff004089e19040 >> x26: ffff007effcabc38 x25: 0000000000000000 x24: 0000000000000001 >> x23: ffff80000803be84 x22: 000000000000000c x21: ffffb093e79e2a78 >> x20: 000000000000000c x19: ffff004089e19040 x18: 0000000000000000 >> x17: 0000000000001fad x16: 0000000000000030 x15: 0000000000000000 >> x14: 0000000000000003 x13: 0000000000000000 x12: 0000000000000000 >> x11: 0000000000000001 x10: 0000000000000400 x9 : ffffb093e4cee530 >> x8 : 00000000fffffffe x7 : 0000000000ce168a x6 : 000000000000013e >> x5 : 00000000ffffffe1 x4 : 0000000000000001 x3 : 0000000000000b2a >> x2 : 0000000000000b2a x1 : ffffb093e6d6c510 x0 : 0000000000000001 >> Call trace: >> set_task_cpu+0x188/0x240 >> load_balance+0x5d0/0xc60 >> rebalance_domains+0x26c/0x380 >> _nohz_idle_balance.isra.0+0x1e0/0x370 >> run_rebalance_domains+0x6c/0x80 >> __do_softirq+0x128/0x3d8 >> ____do_softirq+0x18/0x24 >> call_on_irq_stack+0x2c/0x38 >> do_softirq_own_stack+0x24/0x3c >> __irq_exit_rcu+0xcc/0xf4 >> irq_exit_rcu+0x18/0x24 >> el1_interrupt+0x4c/0xe4 >> el1h_64_irq_handler+0x18/0x2c >> el1h_64_irq+0x74/0x78 >> arch_cpu_idle+0x18/0x4c >> default_idle_call+0x58/0x194 >> do_idle+0x244/0x2b0 >> cpu_startup_entry+0x30/0x3c >> secondary_start_kernel+0x14c/0x190 >> __secondary_switched+0xb0/0xb4 >> ---[ end trace 0000000000000000 ]--- >> >> Signed-off-by: Yicong Yang >> --- >> kernel/sched/fair.c | 4 ++++ >> 1 file changed, 4 insertions(+) >> >> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c >> index 7a1b1f855b96..8fe767362d22 100644 >> --- a/kernel/sched/fair.c >> +++ b/kernel/sched/fair.c >> @@ -8433,6 +8433,10 @@ int can_migrate_task(struct task_struct *p, struct lb_env *env) >> if (kthread_is_per_cpu(p)) >> return 0; >> >> + /* Migration disabled tasks need to be kept on their running CPU. */ >> + if (is_migration_disabled(p)) >> + return 0; >> + >> if (!cpumask_test_cpu(env->dst_cpu, p->cpus_ptr)) { >> int cpu; >> >> -- >> 2.24.0 >> > Looks reasonable to me. Would it be possible to also update the comments at the beginning of > can_migrate_task() starts with: "We do not migrate tasks that are:" > Thanks for the suggestion! It seems only uncommented conditions are summarized in that graph, otherwise they're mentioned close to there branch like kthread_is_per_cpu(p) case. I can add it in v2 if you think it'll be useful. > Reviewed-by: Chen Yu Thanks, Yicong > > thanks, > Chenyu > > . >