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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 9A835C433DF for ; Mon, 18 May 2020 19:00:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7926F207FB for ; Mon, 18 May 2020 19:00:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729199AbgERS7t (ORCPT ); Mon, 18 May 2020 14:59:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43782 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728967AbgERS7k (ORCPT ); Mon, 18 May 2020 14:59:40 -0400 Received: from Galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9421FC061A0C for ; Mon, 18 May 2020 11:59:40 -0700 (PDT) Received: from p5de0bf0b.dip0.t-ipconnect.de ([93.224.191.11] helo=nanos.tec.linutronix.de) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1jakz6-0002L7-67; Mon, 18 May 2020 20:59:32 +0200 Received: by nanos.tec.linutronix.de (Postfix, from userid 1000) id 9E621100606; Mon, 18 May 2020 20:59:31 +0200 (CEST) From: Thomas Gleixner To: Christoph Hellwig Cc: Christoph Hellwig , Ming Lei , linux-block@vger.kernel.org, John Garry , Bart Van Assche , Hannes Reinecke Subject: Re: [PATCH 5/9] blk-mq: don't set data->ctx and data->hctx in blk_mq_alloc_request_hctx In-Reply-To: <20200518184543.GA26157@lst.de> References: <20200518093155.GB35380@T590> <87imgty15d.fsf@nanos.tec.linutronix.de> <20200518115454.GA46364@T590> <20200518131634.GA645@lst.de> <20200518141107.GA50374@T590> <20200518165619.GA17465@lst.de> <87o8qlw0kz.fsf@nanos.tec.linutronix.de> <20200518184543.GA26157@lst.de> Date: Mon, 18 May 2020 20:59:31 +0200 Message-ID: <87eerhvzl8.fsf@nanos.tec.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org Christoph Hellwig writes: > On Mon, May 18, 2020 at 08:38:04PM +0200, Thomas Gleixner wrote: >> > Shouldn't all the per-cpu kthreads also stop as part of the offlining? >> > If they don't quiesce before the new blk-mq stop state I think we need >> > to make sure they do. It is rather pointless to quiesce the requests >> > if a thread that can submit I/O is still live. >> >> Which kthreads are you talking about? > > I think PF_KTHREAD threads bound to single cpu will usually be > workqueues, yes. > >> Workqueues? CPU bound workqueues are shut down in >> CPUHP_AP_WORKQUEUE_ONLINE state. > > That's what I mean. If we shut down I/O before that happend we'd have > a problem, but as I expected your state machine is smarter than that :) It would have been a problem with the old notifier mess to actually figure out what runs when. But with the explicit states it should be pretty easy to find a spot which meets your requirements :) Thanks, tglx