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 B931FC433E0 for ; Wed, 20 May 2020 19:41:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 91940207D3 for ; Wed, 20 May 2020 19:41:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726846AbgETTlS (ORCPT ); Wed, 20 May 2020 15:41:18 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48744 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726548AbgETTlS (ORCPT ); Wed, 20 May 2020 15:41:18 -0400 Received: from Galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8A48FC061A0E; Wed, 20 May 2020 12:41:18 -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 1jbUaQ-0001RU-Cr; Wed, 20 May 2020 21:41:06 +0200 Received: by nanos.tec.linutronix.de (Postfix, from userid 1000) id D65F4100C99; Wed, 20 May 2020 21:41:05 +0200 (CEST) From: Thomas Gleixner To: Jens Axboe , Christoph Hellwig , Ming Lei Cc: linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, John Garry , Bart Van Assche , Hannes Reinecke , io-uring@vger.kernel.org Subject: Re: io_uring vs CPU hotplug, was Re: [PATCH 5/9] blk-mq: don't set data->ctx and data->hctx in blk_mq_alloc_request_hctx In-Reply-To: <448d3660-0d83-889b-001f-a09ea53fa117@kernel.dk> References: <20200518093155.GB35380@T590> <87imgty15d.fsf@nanos.tec.linutronix.de> <20200518115454.GA46364@T590> <20200518131634.GA645@lst.de> <20200518141107.GA50374@T590> <20200518165619.GA17465@lst.de> <20200519015420.GA70957@T590> <20200519153000.GB22286@lst.de> <20200520011823.GA415158@T590> <20200520030424.GI416136@T590> <20200520080357.GA4197@lst.de> <8f893bb8-66a9-d311-ebd8-d5ccd8302a0d@kernel.dk> <448d3660-0d83-889b-001f-a09ea53fa117@kernel.dk> Date: Wed, 20 May 2020 21:41:05 +0200 Message-ID: <87tv0av1gu.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 Jens Axboe writes: > On 5/20/20 8:45 AM, Jens Axboe wrote: >> It just uses kthread_create_on_cpu(), nothing home grown. Pretty sure >> they just break affinity if that CPU goes offline. > > Just checked, and it works fine for me. If I create an SQPOLL ring with > SQ_AFF set and bound to CPU 3, if CPU 3 goes offline, then the kthread > just appears unbound but runs just fine. When CPU 3 comes online again, > the mask appears correct. When exactly during the unplug operation is it unbound? Thanks, tglx