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=-9.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,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 D1A39C43381 for ; Mon, 18 Feb 2019 14:05:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A4DE32190C for ; Mon, 18 Feb 2019 14:05:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1550498713; bh=m0xPj6jvTZcAKAV/6fKyEBSAgdw+WVmBWOi2eEFi+QY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=wiwzZg6vRleiinJHUbTuBGhB5yJeUsuaokrMfphtdnxrlubrurBxWTfOzbJ4N/lrQ yvyabeu2Y4aCQK0lzbJ4nxJAypVXDQuI6w2sxd7p5aqLA55VtudIlX0O0RZXAgaBRI lte7POpP39E3eQ1O6Q4vrqyYRUbLkEC4sBJRVx/M= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390100AbfBROFM (ORCPT ); Mon, 18 Feb 2019 09:05:12 -0500 Received: from mail.kernel.org ([198.145.29.99]:47876 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389556AbfBROFK (ORCPT ); Mon, 18 Feb 2019 09:05:10 -0500 Received: from localhost (5356596B.cm-6-7b.dynamic.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 2B4B821901; Mon, 18 Feb 2019 14:05:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1550498708; bh=m0xPj6jvTZcAKAV/6fKyEBSAgdw+WVmBWOi2eEFi+QY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=mfGExCJqgBjMr05sRccBMf91rmw9x1Ygdf35keYtSWACOlR1R8lRG7TShzG6nKJLS 5Qsg+bIOx6JR9yTzNxhQU0E6/8y9NkE25s4n3AZFHp7QmevROACAQhb4/PKuZjRedX URI9+ISxr+TePZ2y8I/0D0nYDXmLkHTHoYYulAM4= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Tetsuo Handa , "Paul E. McKenney" , Petr Mladek , Sergey Senozhatsky , Dmitry Vyukov , "Rafael J. Wysocki" , Vitaly Kuznetsov , Andrew Morton , Linus Torvalds , Sasha Levin Subject: [PATCH 4.4 070/143] kernel/hung_task.c: break RCU locks based on jiffies Date: Mon, 18 Feb 2019 14:43:18 +0100 Message-Id: <20190218133531.653139117@linuxfoundation.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190218133529.099444112@linuxfoundation.org> References: <20190218133529.099444112@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review X-Patchwork-Hint: ignore MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ [ Upstream commit 304ae42739b108305f8d7b3eb3c1aec7c2b643a9 ] check_hung_uninterruptible_tasks() is currently calling rcu_lock_break() for every 1024 threads. But check_hung_task() is very slow if printk() was called, and is very fast otherwise. If many threads within some 1024 threads called printk(), the RCU grace period might be extended enough to trigger RCU stall warnings. Therefore, calling rcu_lock_break() for every some fixed jiffies will be safer. Link: http://lkml.kernel.org/r/1544800658-11423-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp Signed-off-by: Tetsuo Handa Acked-by: Paul E. McKenney Cc: Petr Mladek Cc: Sergey Senozhatsky Cc: Dmitry Vyukov Cc: "Rafael J. Wysocki" Cc: Vitaly Kuznetsov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin --- kernel/hung_task.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/kernel/hung_task.c b/kernel/hung_task.c index e0f90c2b57aa..cc05b97ba569 100644 --- a/kernel/hung_task.c +++ b/kernel/hung_task.c @@ -30,7 +30,7 @@ int __read_mostly sysctl_hung_task_check_count = PID_MAX_LIMIT; * is disabled during the critical section. It also controls the size of * the RCU grace period. So it needs to be upper-bound. */ -#define HUNG_TASK_BATCHING 1024 +#define HUNG_TASK_LOCK_BREAK (HZ / 10) /* * Zero means infinite timeout - no checking done: @@ -158,7 +158,7 @@ static bool rcu_lock_break(struct task_struct *g, struct task_struct *t) static void check_hung_uninterruptible_tasks(unsigned long timeout) { int max_count = sysctl_hung_task_check_count; - int batch_count = HUNG_TASK_BATCHING; + unsigned long last_break = jiffies; struct task_struct *g, *t; /* @@ -172,10 +172,10 @@ static void check_hung_uninterruptible_tasks(unsigned long timeout) for_each_process_thread(g, t) { if (!max_count--) goto unlock; - if (!--batch_count) { - batch_count = HUNG_TASK_BATCHING; + if (time_after(jiffies, last_break + HUNG_TASK_LOCK_BREAK)) { if (!rcu_lock_break(g, t)) goto unlock; + last_break = jiffies; } /* use "==" to skip the TASK_KILLABLE tasks waiting on NFS */ if (t->state == TASK_UNINTERRUPTIBLE) -- 2.19.1