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=-10.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 8ABCCC433E0 for ; Thu, 14 Jan 2021 13:13:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3FD8223A59 for ; Thu, 14 Jan 2021 13:13:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728607AbhANNNA (ORCPT ); Thu, 14 Jan 2021 08:13:00 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48440 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725955AbhANNM7 (ORCPT ); Thu, 14 Jan 2021 08:12:59 -0500 Received: from merlin.infradead.org (merlin.infradead.org [IPv6:2001:8b0:10b:1231::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 73B0CC061574 for ; Thu, 14 Jan 2021 05:12:19 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=ebUnZW1AQJPxu5ojrsJH28XYwALDU7JpBf3f9D5JPLU=; b=FXvCqXrgoZHAOqcfePOMT7FEk1 qW4DAd7/juGkGp5obAzy7Gnu9EGmQaNi07iKLs00USXWybUA1jF0flosDvHBMP2y0kbVm4HYYHZnJ Qoh2BJJiTqc/n+Mrnnu1DLEkiDINsU9HK/W4ulQR0MfNWScTt1DGzEmVUnfygf72uaaHvpsMd0HTn zUarKieqWuwgWqRATa3+6jMCQ6dCYoqqCFyIbVMY0ZQJa3ZyYGq4LO2F9Mq0QHYWG4HbeuMU1NiWD 4jc+e6m5CQoGXhCys5J0Aaj28SJ1HNaAaTOu5KE8JhhaDunw4J0B+PAwum20ZFLAh23QAXVc26iKV VqFWUYmQ==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1l02Q2-0005zR-6d; Thu, 14 Jan 2021 13:12:06 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 25CA1301324; Thu, 14 Jan 2021 14:12:04 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id EA8B8200D400B; Thu, 14 Jan 2021 14:12:03 +0100 (CET) Date: Thu, 14 Jan 2021 14:12:03 +0100 From: Peter Zijlstra To: Lai Jiangshan Cc: Ingo Molnar , Thomas Gleixner , LKML , Valentin Schneider , Qian Cai , Vincent Donnefort , Dexuan Cui , "Paul E. McKenney" , Vincent Guittot , Steven Rostedt , Tejun Heo Subject: Re: [PATCH 3/4] workqueue: Tag bound workers with KTHREAD_IS_PER_CPU Message-ID: References: <20210112144344.850850975@infradead.org> <20210112144843.849135905@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 13, 2021 at 09:28:13PM +0800, Lai Jiangshan wrote: > On Tue, Jan 12, 2021 at 10:51 PM Peter Zijlstra wrote: > > @@ -4972,9 +4977,11 @@ static void rebind_workers(struct worker > > * of all workers first and then clear UNBOUND. As we're called > > * from CPU_ONLINE, the following shouldn't fail. > > */ > > - for_each_pool_worker(worker, pool) > > + for_each_pool_worker(worker, pool) { > > WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, > > pool->attrs->cpumask) < 0); > > + kthread_set_per_cpu(worker->task, true); > > Will the schedule break affinity in the middle of these two lines due to > patch4 allowing it and result in Paul's reported splat. So something like the below _should_ work, except i'm seeing odd WARNs. I'll prod at it some more. --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -2371,6 +2371,7 @@ static int worker_thread(void *__worker) /* tell the scheduler that this is a workqueue worker */ set_pf_worker(true); woke_up: + kthread_parkme(); raw_spin_lock_irq(&pool->lock); /* am I supposed to die? */ @@ -2428,6 +2429,7 @@ static int worker_thread(void *__worker) move_linked_works(work, &worker->scheduled, NULL); process_scheduled_works(worker); } + kthread_parkme(); } while (keep_working(pool)); worker_set_flags(worker, WORKER_PREP); @@ -4978,9 +4980,9 @@ static void rebind_workers(struct worker * from CPU_ONLINE, the following shouldn't fail. */ for_each_pool_worker(worker, pool) { - WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, - pool->attrs->cpumask) < 0); + kthread_park(worker->task); kthread_set_per_cpu(worker->task, true); + kthread_unpark(worker->task); } raw_spin_lock_irq(&pool->lock);