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=-9.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 9F5BFC433E1 for ; Fri, 19 Jun 2020 14:59:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7127821941 for ; Fri, 19 Jun 2020 14:59:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1592578742; bh=d3O9zOtYniC+zJb0zbzXf97OfdLaMig2KROpDOE/psc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=Db1XhMeXzayCkqzk2SYt9SyjT6r/B9DDq/mPWM6wuEcUEg4DnaV9PAy8CNrMdkMax UGPRMm+5e49otl52ruP4nY26PvcVE9lxX2COvGlP26z1w7Qclh1nQipu4XLHMbF+SR OikFWrtDcbSEORfaoUazyomAH/ToFuE68UB5HuBk= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390452AbgFSO7A (ORCPT ); Fri, 19 Jun 2020 10:59:00 -0400 Received: from mail.kernel.org ([198.145.29.99]:54828 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2390442AbgFSO6y (ORCPT ); Fri, 19 Jun 2020 10:58:54 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 9E6E8218AC; Fri, 19 Jun 2020 14:58:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1592578733; bh=d3O9zOtYniC+zJb0zbzXf97OfdLaMig2KROpDOE/psc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=lYMYXTG88uS3kfFk6P3F37KEDu32gQsHB4DXy2GnFOxNuwMVxaoAXl89ux9Hq7jgt 7h4WDdD8BYFPXgWyYPt+A2uOUwEGvVRVsK+sxzsm8cdtNP7KPjBePRqqhdLQV6MIoY +T55ePkyrEZWcYTfAB3bicTYWQY/fWf8rBUhy6os= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, "Peter Zijlstra (Intel)" , Qian Cai , Sasha Levin , Michael Ellerman Subject: [PATCH 4.19 136/267] sched/core: Fix illegal RCU from offline CPUs Date: Fri, 19 Jun 2020 16:32:01 +0200 Message-Id: <20200619141655.349082479@linuxfoundation.org> X-Mailer: git-send-email 2.27.0 In-Reply-To: <20200619141648.840376470@linuxfoundation.org> References: <20200619141648.840376470@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Peter Zijlstra [ Upstream commit bf2c59fce4074e55d622089b34be3a6bc95484fb ] In the CPU-offline process, it calls mmdrop() after idle entry and the subsequent call to cpuhp_report_idle_dead(). Once execution passes the call to rcu_report_dead(), RCU is ignoring the CPU, which results in lockdep complaining when mmdrop() uses RCU from either memcg or debugobjects below. Fix it by cleaning up the active_mm state from BP instead. Every arch which has CONFIG_HOTPLUG_CPU should have already called idle_task_exit() from AP. The only exception is parisc because it switches them to &init_mm unconditionally (see smp_boot_one_cpu() and smp_cpu_init()), but the patch will still work there because it calls mmgrab(&init_mm) in smp_cpu_init() and then should call mmdrop(&init_mm) in finish_cpu(). WARNING: suspicious RCU usage ----------------------------- kernel/workqueue.c:710 RCU or wq_pool_mutex should be held! other info that might help us debug this: RCU used illegally from offline CPU! Call Trace: dump_stack+0xf4/0x164 (unreliable) lockdep_rcu_suspicious+0x140/0x164 get_work_pool+0x110/0x150 __queue_work+0x1bc/0xca0 queue_work_on+0x114/0x120 css_release+0x9c/0xc0 percpu_ref_put_many+0x204/0x230 free_pcp_prepare+0x264/0x570 free_unref_page+0x38/0xf0 __mmdrop+0x21c/0x2c0 idle_task_exit+0x170/0x1b0 pnv_smp_cpu_kill_self+0x38/0x2e0 cpu_die+0x48/0x64 arch_cpu_idle_dead+0x30/0x50 do_idle+0x2f4/0x470 cpu_startup_entry+0x38/0x40 start_secondary+0x7a8/0xa80 start_secondary_resume+0x10/0x14 Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Qian Cai Signed-off-by: Peter Zijlstra (Intel) Acked-by: Michael Ellerman (powerpc) Link: https://lkml.kernel.org/r/20200401214033.8448-1-cai@lca.pw Signed-off-by: Sasha Levin --- arch/powerpc/platforms/powernv/smp.c | 1 - include/linux/sched/mm.h | 2 ++ kernel/cpu.c | 18 +++++++++++++++++- kernel/sched/core.c | 5 +++-- 4 files changed, 22 insertions(+), 4 deletions(-) diff --git a/arch/powerpc/platforms/powernv/smp.c b/arch/powerpc/platforms/powernv/smp.c index 3d3c989e44dd..8d49ba370c50 100644 --- a/arch/powerpc/platforms/powernv/smp.c +++ b/arch/powerpc/platforms/powernv/smp.c @@ -171,7 +171,6 @@ static void pnv_smp_cpu_kill_self(void) /* Standard hot unplug procedure */ idle_task_exit(); - current->active_mm = NULL; /* for sanity */ cpu = smp_processor_id(); DBG("CPU%d offline\n", cpu); generic_set_cpu_dead(cpu); diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h index e9d4e389aed9..766bbe813861 100644 --- a/include/linux/sched/mm.h +++ b/include/linux/sched/mm.h @@ -49,6 +49,8 @@ static inline void mmdrop(struct mm_struct *mm) __mmdrop(mm); } +void mmdrop(struct mm_struct *mm); + /* * This has to be called after a get_task_mm()/mmget_not_zero() * followed by taking the mmap_sem for writing before modifying the diff --git a/kernel/cpu.c b/kernel/cpu.c index 6d6c106a495c..08b9d6ba0807 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -3,6 +3,7 @@ * * This code is licenced under the GPL. */ +#include #include #include #include @@ -532,6 +533,21 @@ static int bringup_cpu(unsigned int cpu) return bringup_wait_for_ap(cpu); } +static int finish_cpu(unsigned int cpu) +{ + struct task_struct *idle = idle_thread_get(cpu); + struct mm_struct *mm = idle->active_mm; + + /* + * idle_task_exit() will have switched to &init_mm, now + * clean up any remaining active_mm state. + */ + if (mm != &init_mm) + idle->active_mm = &init_mm; + mmdrop(mm); + return 0; +} + /* * Hotplug state machine related functions */ @@ -1379,7 +1395,7 @@ static struct cpuhp_step cpuhp_hp_states[] = { [CPUHP_BRINGUP_CPU] = { .name = "cpu:bringup", .startup.single = bringup_cpu, - .teardown.single = NULL, + .teardown.single = finish_cpu, .cant_stop = true, }, /* Final state before CPU kills itself */ diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 2befd2c4ce9e..0325ccf3a8e4 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -5571,13 +5571,14 @@ void idle_task_exit(void) struct mm_struct *mm = current->active_mm; BUG_ON(cpu_online(smp_processor_id())); + BUG_ON(current != this_rq()->idle); if (mm != &init_mm) { switch_mm(mm, &init_mm, current); - current->active_mm = &init_mm; finish_arch_post_lock_switch(); } - mmdrop(mm); + + /* finish_cpu(), as ran on the BP, will clean up the active_mm state */ } /* -- 2.25.1