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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=ham 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 E4FA9C3A5A6 for ; Mon, 23 Sep 2019 14:17:07 +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 BF3C9207FD for ; Mon, 23 Sep 2019 14:17:07 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BF3C9207FD 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]:57150 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iCP9G-0007kg-J9 for qemu-devel@archiver.kernel.org; Mon, 23 Sep 2019 10:17:06 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:36714) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iCP6u-0006Um-F7 for qemu-devel@nongnu.org; Mon, 23 Sep 2019 10:14:42 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1iCP6t-0006QF-61 for qemu-devel@nongnu.org; Mon, 23 Sep 2019 10:14:40 -0400 Received: from mx1.redhat.com ([209.132.183.28]:38348) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1iCP6p-0006PU-Qh; Mon, 23 Sep 2019 10:14:36 -0400 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 mx1.redhat.com (Postfix) with ESMTPS id 21C5410CC1FA; Mon, 23 Sep 2019 14:14:35 +0000 (UTC) Received: from [10.3.116.249] (ovpn-116-249.phx2.redhat.com [10.3.116.249]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 901BB5D9D5; Mon, 23 Sep 2019 14:14:30 +0000 (UTC) Subject: Re: [PATCH] nbd: Grab aio context lock in more places To: Sergio Lopez References: <20190917023917.32226-1-eblake@redhat.com> <87d0frcdd8.fsf@redhat.com> From: Eric Blake Openpgp: preference=signencrypt Autocrypt: addr=eblake@redhat.com; keydata= xsBNBEvHyWwBCACw7DwsQIh0kAbUXyqhfiKAKOTVu6OiMGffw2w90Ggrp4bdVKmCaEXlrVLU xphBM8mb+wsFkU+pq9YR621WXo9REYVIl0FxKeQo9dyQBZ/XvmUMka4NOmHtFg74nvkpJFCD TUNzmqfcjdKhfFV0d7P/ixKQeZr2WP1xMcjmAQY5YvQ2lUoHP43m8TtpB1LkjyYBCodd+LkV GmCx2Bop1LSblbvbrOm2bKpZdBPjncRNob73eTpIXEutvEaHH72LzpzksfcKM+M18cyRH+nP sAd98xIbVjm3Jm4k4d5oQyE2HwOur+trk2EcxTgdp17QapuWPwMfhaNq3runaX7x34zhABEB AAHNHkVyaWMgQmxha2UgPGVibGFrZUByZWRoYXQuY29tPsLAegQTAQgAJAIbAwULCQgHAwUV CgkICwUWAgMBAAIeAQIXgAUCS8fL9QIZAQAKCRCnoWtKJSdDahBHCACbl/5FGkUqJ89GAjeX RjpAeJtdKhujir0iS4CMSIng7fCiGZ0fNJCpL5RpViSo03Q7l37ss+No+dJI8KtAp6ID+PMz wTJe5Egtv/KGUKSDvOLYJ9WIIbftEObekP+GBpWP2+KbpADsc7EsNd70sYxExD3liwVJYqLc Rw7so1PEIFp+Ni9A1DrBR5NaJBnno2PHzHPTS9nmZVYm/4I32qkLXOcdX0XElO8VPDoVobG6 gELf4v/vIImdmxLh/w5WctUpBhWWIfQDvSOW2VZDOihm7pzhQodr3QP/GDLfpK6wI7exeu3P pfPtqwa06s1pae3ad13mZGzkBdNKs1HEm8x6zsBNBEvHyWwBCADGkMFzFjmmyqAEn5D+Mt4P zPdO8NatsDw8Qit3Rmzu+kUygxyYbz52ZO40WUu7EgQ5kDTOeRPnTOd7awWDQcl1gGBXgrkR pAlQ0l0ReO57Q0eglFydLMi5bkwYhfY+TwDPMh3aOP5qBXkm4qIYSsxb8A+i00P72AqFb9Q7 3weG/flxSPApLYQE5qWGSXjOkXJv42NGS6o6gd4RmD6Ap5e8ACo1lSMPfTpGzXlt4aRkBfvb NCfNsQikLZzFYDLbQgKBA33BDeV6vNJ9Cj0SgEGOkYyed4I6AbU0kIy1hHAm1r6+sAnEdIKj cHi3xWH/UPrZW5flM8Kqo14OTDkI9EtlABEBAAHCwF8EGAEIAAkFAkvHyWwCGwwACgkQp6Fr SiUnQ2q03wgAmRFGDeXzc58NX0NrDijUu0zx3Lns/qZ9VrkSWbNZBFjpWKaeL1fdVeE4TDGm I5mRRIsStjQzc2R9b+2VBUhlAqY1nAiBDv0Qnt+9cLiuEICeUwlyl42YdwpmY0ELcy5+u6wz mK/jxrYOpzXKDwLq5k4X+hmGuSNWWAN3gHiJqmJZPkhFPUIozZUCeEc76pS/IUN72NfprZmF Dp6/QDjDFtfS39bHSWXKVZUbqaMPqlj/z6Ugk027/3GUjHHr8WkeL1ezWepYDY7WSoXwfoAL 2UXYsMAr/uUncSKlfjvArhsej0S4zbqim2ZY6S8aRWw94J3bSvJR+Nwbs34GPTD4Pg== Organization: Red Hat, Inc. Message-ID: <821c8483-44b0-0c6b-12af-f72984ed19ff@redhat.com> Date: Mon, 23 Sep 2019 09:14:29 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <87d0frcdd8.fsf@redhat.com> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="dlckrLlSNZ7RQRAZZrCOTQ4Kvu9ebc9HA" X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.6.2 (mx1.redhat.com [10.5.110.65]); Mon, 23 Sep 2019 14:14:35 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 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: kwolf@redhat.com, qemu-devel@nongnu.org, "open list:Network Block Dev..." , Max Reitz Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --dlckrLlSNZ7RQRAZZrCOTQ4Kvu9ebc9HA Content-Type: multipart/mixed; boundary="AbWWABeXBqQlcE8lWJEbuuBYQefpRQ8vk"; protected-headers="v1" From: Eric Blake To: Sergio Lopez Cc: qemu-devel@nongnu.org, kwolf@redhat.com, Max Reitz , "open list:Network Block Dev..." Message-ID: <821c8483-44b0-0c6b-12af-f72984ed19ff@redhat.com> Subject: Re: [PATCH] nbd: Grab aio context lock in more places References: <20190917023917.32226-1-eblake@redhat.com> <87d0frcdd8.fsf@redhat.com> In-Reply-To: <87d0frcdd8.fsf@redhat.com> --AbWWABeXBqQlcE8lWJEbuuBYQefpRQ8vk Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 9/23/19 9:10 AM, Sergio Lopez wrote: >=20 > Eric Blake writes: >=20 >> When iothreads are in use, the failure to grab the aio context results= >> in an assertion failure when trying to unlock things during blk_unref,= >> when trying to unlock a mutex that was not locked. In short, all >> calls to nbd_export_put need to done while within the correct aio >> context. But since nbd_export_put can recursively reach itself via >> nbd_export_close, and recursively grabbing the context would deadlock,= >> we can't do the context grab directly in those functions, but must do >> so in their callers. >> >> Hoist the use of the correct aio_context from nbd_export_new() to its >> caller qmp_nbd_server_add(). Then tweak qmp_nbd_server_remove(), >> nbd_eject_notifier(), and nbd_esport_close_all() to grab the right >> context, so that all callers during qemu now own the context before >> nbd_export_put() can call blk_unref(). >> >> Remaining uses in qemu-nbd don't matter (since that use case does not >> support iothreads). >> >> Suggested-by: Kevin Wolf >> Signed-off-by: Eric Blake >> --- >> >> With this in place, my emailed formula [1] for causing an iothread >> assertion failure no longer hits, and all the -nbd and -qcow2 iotests >> still pass. I would still like to update iotests to cover things (I >> could not quickly figure out how to make iotest 222 use iothreads - >> either we modify that one or add a new one), but wanted to get review >> started on this first. >> >> [1] https://lists.gnu.org/archive/html/qemu-devel/2019-09/msg03383.htm= l I ended up patch 223 instead, as patch 2/1 in reply to the original. >> void nbd_export_close(NBDExport *exp) >> { >> NBDClient *client, *next; >> >> nbd_export_get(exp); >> + >=20 > I'm not sure if this new line was added here on purpose. >=20 Spurious leftovers from an alternative attempt. Will drop this. >> /* >> * TODO: Should we expand QMP NbdServerRemoveNode enum to allow a= >> * close mode that stops advertising the export to new clients bu= t >> @@ -1684,9 +1695,13 @@ BlockBackend *nbd_export_get_blockdev(NBDExport= *exp) >> void nbd_export_close_all(void) >> { >> NBDExport *exp, *next; >> + AioContext *aio_context; >> >> QTAILQ_FOREACH_SAFE(exp, &exports, next, next) { >> + aio_context =3D exp->ctx; >> + aio_context_acquire(aio_context); >> nbd_export_close(exp); >> + aio_context_release(aio_context); >> } >> } >=20 > Otherwise, LGTM. >=20 > Reviewed-by: Sergio Lopez >=20 Thanks; queuing this on my NBD tree, along with the iotest followup (although there's still a bit of time for that to get a review before I send the pull request later today). --=20 Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org --AbWWABeXBqQlcE8lWJEbuuBYQefpRQ8vk-- --dlckrLlSNZ7RQRAZZrCOTQ4Kvu9ebc9HA Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEccLMIrHEYCkn0vOqp6FrSiUnQ2oFAl2I00UACgkQp6FrSiUn Q2p5rgf/XEUgkiZzu29JtqSAzXx0FZrLIQGHKfat0SXCDbb5KAPaGjcanEhPz3ye 2GL8bDhRnYiRMxHPTlStWJsDlWKkMwlPtjYAQEEhg6h4mnpCnykGdqCunnCqo8gY 4yCTC9O3XcHG44EyFKdvltK7qQP2MtR5t4aXa7gzOq0b7HdqYJE7p2mdgNKnHCBg 0P2exSVhNDZFHsJrm137vSUGxM0fPLdfJhb70RcTgYfHsV+nudF8n0XpROckiR75 KwwNdBowfjpaAnSAmTsWg08ZfLA97z1OlRZZgmHf7S27iVP4k71hx4X6BBocLuVE dMmM43xGFCSmP67YEkDpPjqn+NfsCg== =GTVp -----END PGP SIGNATURE----- --dlckrLlSNZ7RQRAZZrCOTQ4Kvu9ebc9HA--