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 5DEBFC433DF for ; Wed, 20 May 2020 03:04:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1D02F2070A for ; Wed, 20 May 2020 03:04:44 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="OI8xrvd+" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726379AbgETDEn (ORCPT ); Tue, 19 May 2020 23:04:43 -0400 Received: from us-smtp-1.mimecast.com ([205.139.110.61]:34355 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726318AbgETDEn (ORCPT ); Tue, 19 May 2020 23:04:43 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1589943882; 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=R73O4aUb2p7w01cdPQS1ezbGo2TrRH6uTOtAEoGytJg=; b=OI8xrvd+rtFND7NoO6/+gGZtTr09IlPCATW572Ei3lxtXSZdJTaZ3aimZ5ovZdBjS8JN3c gfKknmZt8/SLZrDMOUFRAktmvoxSbza9dqbhAe9zV2gNDtHPdnH1CiGnHnG9y1KU/tJg2a 6yPrJMFvj13Iam0czFPccRmT+JWC19s= 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-100-zX1buEnGN9Ke__JvbqtseA-1; Tue, 19 May 2020 23:04:37 -0400 X-MC-Unique: zX1buEnGN9Ke__JvbqtseA-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 9539C8018A2; Wed, 20 May 2020 03:04:36 +0000 (UTC) Received: from T590 (ovpn-12-217.pek2.redhat.com [10.72.12.217]) by smtp.corp.redhat.com (Postfix) with ESMTPS id C6085261A1; Wed, 20 May 2020 03:04:29 +0000 (UTC) Date: Wed, 20 May 2020 11:04:24 +0800 From: Ming Lei To: Christoph Hellwig , linux-kernel@vger.kernel.org Cc: Thomas Gleixner , 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 Message-ID: <20200520030424.GI416136@T590> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200520011823.GA415158@T590> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Wed, May 20, 2020 at 09:18:23AM +0800, Ming Lei wrote: > On Tue, May 19, 2020 at 05:30:00PM +0200, Christoph Hellwig wrote: > > On Tue, May 19, 2020 at 09:54:20AM +0800, Ming Lei wrote: > > > As Thomas clarified, workqueue hasn't such issue any more, and only other > > > per CPU kthreads can run until the CPU clears the online bit. > > > > > > So the question is if IO can be submitted from such kernel context? > > > > What other per-CPU kthreads even exist? > > I don't know, so expose to wider audiences. One user is io uring with IORING_SETUP_SQPOLL & IORING_SETUP_SQ_AFF, see io_sq_offload_start(), and it is a IO submission kthread. Thanks, Ming