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=-0.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 E7A9CC47254 for ; Wed, 6 May 2020 01:24:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BCBDF20735 for ; Wed, 6 May 2020 01:24:44 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="DeEFxxGc" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729744AbgEFBYo (ORCPT ); Tue, 5 May 2020 21:24:44 -0400 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:48612 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1729457AbgEFBYn (ORCPT ); Tue, 5 May 2020 21:24:43 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1588728282; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=Tt4i4Nh4xWPSAsQ3lja/irt2LqFsTaeYy4zp5iGG8yk=; b=DeEFxxGc+8HDQXdCE1RkRQJLinkXTQE5SB23tlCzMDw0+9DAPxuX3ZnqbILgtA84LYxAGd pqlrz6FjQ52bnQHKWjbdyQ1zMXaeEfSnLvWiu5fuCilG8CjF/fZHBJQYhcsigLMjLOV3q5 qrG8nw3xBoD24cid5dCkSnfzuXth9rQ= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-163-285rhgcbONKCUKzQNhiBeg-1; Tue, 05 May 2020 21:24:40 -0400 X-MC-Unique: 285rhgcbONKCUKzQNhiBeg-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 38CA5800687; Wed, 6 May 2020 01:24:39 +0000 (UTC) Received: from T590 (ovpn-8-23.pek2.redhat.com [10.72.8.23]) by smtp.corp.redhat.com (Postfix) with ESMTPS id CAD8264431; Wed, 6 May 2020 01:24:30 +0000 (UTC) Date: Wed, 6 May 2020 09:24:25 +0800 From: Ming Lei To: Christoph Hellwig Cc: Will Deacon , Peter Zijlstra , Jens Axboe , linux-block@vger.kernel.org, John Garry , Bart Van Assche , Hannes Reinecke , Thomas Gleixner , paulmck@kernel.org Subject: Re: [PATCH V8 07/11] blk-mq: stop to handle IO and drain IO before hctx becomes inactive Message-ID: <20200506012425.GA1177270@T590> References: <20200429021612.GD671522@T590> <20200429080728.GB29143@willie-the-truck> <20200429094616.GB700644@T590> <20200429122757.GA30247@willie-the-truck> <20200429134327.GC700644@T590> <20200429173400.GC30247@willie-the-truck> <20200430003945.GA719313@T590> <20200430110429.GI19932@willie-the-truck> <20200430140254.GA996887@T590> <20200505154618.GA3644@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200505154618.GA3644@lst.de> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Tue, May 05, 2020 at 05:46:18PM +0200, Christoph Hellwig wrote: > On Thu, Apr 30, 2020 at 10:02:54PM +0800, Ming Lei wrote: > > BLK_MQ_S_INACTIVE is only set when the last cpu of this hctx is becoming > > offline, and blk_mq_hctx_notify_offline() is called from cpu hotplug > > handler. So if there is any request of this hctx submitted from somewhere, > > it has to this last cpu. That is done by blk-mq's queue mapping. > > > > In case of direct issue, basically blk_mq_get_driver_tag() is run after > > the request is allocated, that is why I mentioned the chance of > > migration is very small. > > "very small" does not cut it, it has to be zero. And it seems the > new version still has this hack. But smp_mb() is used for ordering the WRITE and READ, so it is correct. barrier() is enough when process migration doesn't happen. thank, Ming