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=-9.0 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 708D2C169C4 for ; Mon, 11 Feb 2019 15:54:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 407DB21B18 for ; Mon, 11 Feb 2019 15:54:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1549900454; bh=7zFXGWFKElY8btVisTcELi7OwZcrM7Jyo49hRhizidI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=PE+OiMnFUEn1sWvjxyyqPrLUXjL4R1tcbqkz5iVIf8nFppVANJEINvqp6s+W8YgGM +SryKt+zoksmX50Ax+qRR5ziNn7yTXID8d8hbqtG9lyYGlYx7TLK3pb6i/R3VZ2Mlv RFX26LHiZx2RyAjKEDLaNRUW1I4NWedfVYHB2+UY= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731131AbfBKOfy (ORCPT ); Mon, 11 Feb 2019 09:35:54 -0500 Received: from mail.kernel.org ([198.145.29.99]:44616 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731113AbfBKOfv (ORCPT ); Mon, 11 Feb 2019 09:35:51 -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 68D982080F; Mon, 11 Feb 2019 14:35:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1549895749; bh=7zFXGWFKElY8btVisTcELi7OwZcrM7Jyo49hRhizidI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=U6aNGEw9JN9TmQmVV3Pc+twx5ZKjfkEg9peD2y52fiA6Xh4ZUlRD0fwQJ2ImOvTfD YUxZwAVFbRjHT9HpahB3v0fNLkqj92c/4/c2BpRFWwj/IwCqIoStKwNoRh4kuQl51B MBlAXTUxjwn6Ex3AEKAGyRfBoeInALhC/OjtZr1M= 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 4.20 283/352] kernel/hung_task.c: break RCU locks based on jiffies Date: Mon, 11 Feb 2019 15:18:30 +0100 Message-Id: <20190211141904.940859034@linuxfoundation.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190211141846.543045703@linuxfoundation.org> References: <20190211141846.543045703@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 4.20-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 cb8e3e8ac7b9..444b8b5dd69f 100644 --- a/kernel/hung_task.c +++ b/kernel/hung_task.c @@ -34,7 +34,7 @@ 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: @@ -173,7 +173,7 @@ 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; /* @@ -188,10 +188,10 @@ 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