From patchwork Wed Apr 1 21:40:33 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Qian Cai X-Patchwork-Id: 1265371 Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 48t0Q50HVvz9sPF for ; Thu, 2 Apr 2020 08:56:13 +1100 (AEDT) Authentication-Results: ozlabs.org; dmarc=none (p=none dis=none) header.from=lca.pw Authentication-Results: ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=lca.pw header.i=@lca.pw header.a=rsa-sha256 header.s=google header.b=s8lq9KtN; dkim-atps=neutral Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 48t0Q45vxfzDqyJ for ; Thu, 2 Apr 2020 08:56:12 +1100 (AEDT) X-Original-To: linuxppc-dev@lists.ozlabs.org Delivered-To: linuxppc-dev@lists.ozlabs.org Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=lca.pw (client-ip=2607:f8b0:4864:20::744; helo=mail-qk1-x744.google.com; envelope-from=cai@lca.pw; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=lca.pw Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=lca.pw header.i=@lca.pw header.a=rsa-sha256 header.s=google header.b=s8lq9KtN; dkim-atps=neutral Received: from mail-qk1-x744.google.com (mail-qk1-x744.google.com [IPv6:2607:f8b0:4864:20::744]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 48t04d3LRHzDqnG for ; Thu, 2 Apr 2020 08:41:04 +1100 (AEDT) Received: by mail-qk1-x744.google.com with SMTP id c145so1738534qke.12 for ; Wed, 01 Apr 2020 14:41:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=lca.pw; s=google; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=0RdWMZB6RJn98FXdUSZnSjFG7Se9Mrq9epKZxJ4TlZU=; b=s8lq9KtNGitOmED9ThaQGTb5+/x0rpr3TJKyVHk/V41WssZvfEWTggpVH2Qs+oUCXQ 3zhK1WERFaKh2wtJ8usMb18qkenhhMbR6eEUemwBPcyrjYt0sJ5KDo1VpH86xwfB7zid ugcuvNqf8khkGAEZ0WtHEHdhh0tN07ePRggoKzQa3bocnLkfVVfGKEt3fFN6lOSej2IT cIpt8G9f9DnV5fLPC5Ctvsc0/ghdGF018LKW6vNrTQALlHX5wZ6O+/E7rzWH7OIQ66w5 /isdkpjq0WzlYNkOrWlcADEiGMujKBbHE+ByHfdaRm18AxBexuz/yBeUoOD1kdzWMDW9 vabA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=0RdWMZB6RJn98FXdUSZnSjFG7Se9Mrq9epKZxJ4TlZU=; b=Uy3glt1TlnXH0UZPkrf8GFS0xdLgPKrWERNcEE1iKZFhJ6mvFRJFYNjnJnUacPd5nk +y90RemuXdKsynkYn5S8KG96iC5fvQtFLYXPrpsaLaHERelDpShw/fMpkRQbOhxfXq0J A9B6uFTLoiGssiQT7UzCbqK62ts1u80J9AFps/iFItMs/ABshtSxqruYJrG11XjIZxjj 5sFeuUbI4C5TWKzh9XB6VuOTRMxAdB4NCwYSOo2THTPEa8AShPWqkCELzhI8H/HUVM3B rjc93Ryco9lzJGlA6o17HGNmxrNY5B3pKO9ddfHfvndbXJ96b6naN7kjKx9Rm5/e0JSZ YiTA== X-Gm-Message-State: AGi0PuYLlaGHeIsyHkLsVI4+yepfGX4e8HFPXLxAP9lohDMNkU3AH618 NkpaymWQPpjrvErph9CQoVGw1Q== X-Google-Smtp-Source: APiQypIxrxO6hwyk+9NdzKlR3uKKCXFELr9z5SQnOCvSSKC8X1SAAg+Q+tEpT2bf897wOLX9h+OxAg== X-Received: by 2002:a37:87c7:: with SMTP id j190mr434836qkd.66.1585777261160; Wed, 01 Apr 2020 14:41:01 -0700 (PDT) Received: from ovpn-113-105.phx2.redhat.com (pool-71-184-117-43.bstnma.fios.verizon.net. [71.184.117.43]) by smtp.gmail.com with ESMTPSA id s56sm2456990qtk.9.2020.04.01.14.40.58 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 01 Apr 2020 14:41:00 -0700 (PDT) From: Qian Cai To: peterz@infradead.org, mingo@redhat.com Subject: [PATCH v2] sched/core: fix illegal RCU from offline CPUs Date: Wed, 1 Apr 2020 17:40:33 -0400 Message-Id: <20200401214033.8448-1-cai@lca.pw> X-Mailer: git-send-email 2.21.0 (Apple Git-122.2) MIME-Version: 1.0 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: juri.lelli@redhat.com, James.Bottomley@HansenPartnership.com, vincent.guittot@linaro.org, linux-parisc@vger.kernel.org, paulmck@kernel.org, deller@gmx.de, linux-kernel@vger.kernel.org, rostedt@goodmis.org, bsegall@google.com, linux-mm@kvack.org, Qian Cai , mgorman@suse.de, tglx@linutronix.de, linuxppc-dev@lists.ozlabs.org, dietmar.eggemann@arm.com Errors-To: linuxppc-dev-bounces+patchwork-incoming=ozlabs.org@lists.ozlabs.org Sender: "Linuxppc-dev" From: Peter Zijlstra 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: Qian Cai Acked-by: Michael Ellerman (powerpc) --- 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 13e251699346..b2ba3e95bda7 100644 --- a/arch/powerpc/platforms/powernv/smp.c +++ b/arch/powerpc/platforms/powernv/smp.c @@ -167,7 +167,6 @@ 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 c49257a3b510..a132d875d351 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 2371292f30b0..244d30544377 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -3,6 +3,7 @@ * * This code is licenced under the GPL. */ +#include #include #include #include @@ -564,6 +565,21 @@ 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 */ @@ -1549,7 +1565,7 @@ 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 a2694ba82874..8787958339d5 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -6200,13 +6200,14 @@ 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 */ } /*