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=-8.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 6044CC388F7 for ; Fri, 13 Nov 2020 17:57:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 12198221EB for ; Fri, 13 Nov 2020 17:57:56 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="l+E3WoS3" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725981AbgKMR54 (ORCPT ); Fri, 13 Nov 2020 12:57:56 -0500 Received: from mail.kernel.org ([198.145.29.99]:54392 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725959AbgKMR5z (ORCPT ); Fri, 13 Nov 2020 12:57:55 -0500 Received: from paulmck-ThinkPad-P72.home (50-39-104-11.bvtn.or.frontiernet.net [50.39.104.11]) (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 9F5A6208D5; Fri, 13 Nov 2020 17:57:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1605290274; bh=SPs6ifdr8H4sMKD7ax8Sx6hzwFG4f+SmdudJwla/AAk=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=l+E3WoS3zzxVRAuAt1Dro8+KxAduqsliRUf/i4u9RcbveIlUEvlzRAYv0H4v0t5TM S7TXa5flyp+i/Gg7uImRgq36p+Cxphb4t0TdcayxoIm3j1qD6DL8Kja1+NAfJSMLEL VS9Y3NA3dfrIXdyc1vkm5e3GlMNmW+r3b8mWsX9M= Received: by paulmck-ThinkPad-P72.home (Postfix, from userid 1000) id 4C48D35212DC; Fri, 13 Nov 2020 09:57:54 -0800 (PST) Date: Fri, 13 Nov 2020 09:57:54 -0800 From: "Paul E. McKenney" To: Marco Elver Cc: Steven Rostedt , Anders Roxell , Andrew Morton , Alexander Potapenko , Dmitry Vyukov , Jann Horn , Mark Rutland , Linux Kernel Mailing List , Linux-MM , kasan-dev , rcu@vger.kernel.org, Peter Zijlstra , Tejun Heo , Lai Jiangshan Subject: Re: [PATCH] kfence: Avoid stalling work queue task without allocations Message-ID: <20201113175754.GA6273@paulmck-ThinkPad-P72> Reply-To: paulmck@kernel.org References: <20201111133813.GA81547@elver.google.com> <20201111130543.27d29462@gandalf.local.home> <20201111182333.GA3249@paulmck-ThinkPad-P72> <20201111183430.GN517454@elver.google.com> <20201111192123.GB3249@paulmck-ThinkPad-P72> <20201111202153.GT517454@elver.google.com> <20201112001129.GD3249@paulmck-ThinkPad-P72> <20201112161439.GA2989297@elver.google.com> <20201112175406.GF3249@paulmck-ThinkPad-P72> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201112175406.GF3249@paulmck-ThinkPad-P72> User-Agent: Mutt/1.9.4 (2018-02-28) Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org On Thu, Nov 12, 2020 at 09:54:06AM -0800, Paul E. McKenney wrote: > On Thu, Nov 12, 2020 at 05:14:39PM +0100, Marco Elver wrote: [ . . . ] > > | [ 334.160218] BUG: workqueue lockup - pool cpus=0 node=0 flags=0x0 nice=0 stuck for 15s! > > It might be instructive to cause this code to provoke a backtrace. > I suggest adding something like "trigger_single_cpu_backtrace(cpu)" > in kernel/workqueue.c's function named wq_watchdog_timer_fn() > somewhere within its "if" statement that is preceded with the "did we > stall?" comment. Or just search for "BUG: workqueue lockup - pool" > within kernel/workqueue.c. And I did get a small but unexpected gift of time, so here is an (untested) patch. Thanx, Paul ------------------------------------------------------------------------ diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 437935e..f3d4ff7 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -5792,6 +5792,7 @@ static void wq_watchdog_timer_fn(struct timer_list *unused) pr_cont_pool_info(pool); pr_cont(" stuck for %us!\n", jiffies_to_msecs(jiffies - pool_ts) / 1000); + trigger_single_cpu_backtrace(cpu); } }