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=-6.8 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,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 5E55AC433E6 for ; Mon, 20 Jul 2020 10:03:55 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 2C38921775 for ; Mon, 20 Jul 2020 10:03:55 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Qzb4sQtn" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2C38921775 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:55126 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jxSeI-0005F7-D0 for qemu-devel@archiver.kernel.org; Mon, 20 Jul 2020 06:03:54 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:36856) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jxSdM-0004Ox-4l for qemu-devel@nongnu.org; Mon, 20 Jul 2020 06:02:56 -0400 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:26709 helo=us-smtp-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1jxSdK-0007ou-JT for qemu-devel@nongnu.org; Mon, 20 Jul 2020 06:02:55 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1595239373; 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=AJlrCIn0zLNAOlT71qGNa4prvgmmTm1RhbLt1h0Pd1Q=; b=Qzb4sQtngNrtCFt8JVD6l7Fhp/t83IhoVQww3bL0O+HDuR5olUjaiA+waDFYSM8sQFn9S4 iy26FBj4c4mvyW7DEmfO7eIlX9z+HIWVYJNVZFf5rMisqQ6+5YhFZo12RsF1xC2aGqKRCU dJmgLUEJUw2q+DZXFAebXS/FPUasXWg= 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-121-1u5M7A5CPMGYq21SY-V6iA-1; Mon, 20 Jul 2020 06:02:49 -0400 X-MC-Unique: 1u5M7A5CPMGYq21SY-V6iA-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 7DABD1DE0; Mon, 20 Jul 2020 10:02:48 +0000 (UTC) Received: from localhost (ovpn-114-38.ams2.redhat.com [10.36.114.38]) by smtp.corp.redhat.com (Postfix) with ESMTP id 1247A5D9DD; Mon, 20 Jul 2020 10:02:47 +0000 (UTC) Date: Mon, 20 Jul 2020 11:02:46 +0100 From: Stefan Hajnoczi To: Philippe =?iso-8859-1?Q?Mathieu-Daud=E9?= Subject: Re: [RFC PATCH-for-5.1] hw/ide: Do not block for AIO while resetting a drive Message-ID: <20200720100246.GA24159@stefanha-x1.localdomain> References: <20200717171938.1249-1-f4bug@amsat.org> MIME-Version: 1.0 In-Reply-To: <20200717171938.1249-1-f4bug@amsat.org> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=stefanha@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="EeQfGwPcQSOJBaQU" Content-Disposition: inline Received-SPF: pass client-ip=207.211.31.120; envelope-from=stefanha@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/07/20 03:17:01 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Alexander Bulekov , John Snow , qemu-devel@nongnu.org, qemu-block@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" --EeQfGwPcQSOJBaQU Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, Jul 17, 2020 at 07:19:38PM +0200, Philippe Mathieu-Daud=E9 wrote: > Last minute chat: > 19:01 f4bug: use bdrv_aio_cancel_async() if possible because i= t won't block the current thread. > 19:02 f4bug: For example, in device emulation code where the g= uest has requested to cancel an I/O request it's often possible to use the = async version. > 19:02 f4bug: But in synchronous code like device reset it may = be necessary to use the synchronous (blocking) bdrv_aio_cancel() API instea= d. :( > 19:14 f4bug: The way to decide is: will the current function r= eturn to the event loop and is there someone who will handle the request co= mpletion callback when cancel finishes? > 19:14 f4bug: If the next line of code requires the request to = finished then async cancel cannot be used. > 19:15 f4bug: On the other hand, if the function can return and= it's okay for the request to cancel at some future time then you can use a= sync. >=20 > So I'll revisit this patch :) > --- > hw/ide/core.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) >=20 > diff --git a/hw/ide/core.c b/hw/ide/core.c > index d997a78e47..e3a9ce7d25 100644 > --- a/hw/ide/core.c > +++ b/hw/ide/core.c > @@ -1315,7 +1315,8 @@ static void ide_reset(IDEState *s) > trace_ide_reset(s); > =20 > if (s->pio_aiocb) { > - blk_aio_cancel(s->pio_aiocb); > + /* If there is a pending AIO callback, invoke it now. */ > + blk_aio_cancel_async(s->pio_aiocb); This is a place where an async call is not allowed. The completion function must be called right away (synchronously) before we can continue resetting the device. I sent a patch that allows bdrv_aio_cancel() to find the AioContext so it can call aio_poll(). Stefan --EeQfGwPcQSOJBaQU Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEhpWov9P5fNqsNXdanKSrs4Grc8gFAl8Va8QACgkQnKSrs4Gr c8jUKAgAueuu9GaGkvcRgaEPKb/WwT0G6dI4Lpk6Q5DHxVeLQOA95PeqwGaNtphP SOecf9Ex4f09SjV0m1NK1O7Kqn2K98F+kO3ItyXdy78yyGJLMndhIMUTmjXbkOTR D5a5hWTRwbtpbK1KXQqkbIG0FxxBtDLqaDDyNaJ+kB/t+160MoYLrhzhAwE5GdaX s5TBJaZsjfO7eXkFvxlLQph+msfZyetvRKUCYcKLB9hVGcf6yw3MgGkHDn495zUK gE3vBeHDMhLlwyrCxSsuBdt4KZ+JqaNd/dAQ6YnBCRTnQVO0KJ0UAhUVcxbI5kRd m4/wjQ2rDnSgDQeKWlfg0BjhkReRbg== =fs0p -----END PGP SIGNATURE----- --EeQfGwPcQSOJBaQU--