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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id A2A1DC7EE2E for ; Wed, 7 Jun 2023 18:20:43 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1q6xlA-0005eG-Rj; Wed, 07 Jun 2023 14:19:52 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1q6xl9-0005dk-8E for qemu-devel@nongnu.org; Wed, 07 Jun 2023 14:19:51 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1q6xl7-0003hv-My for qemu-devel@nongnu.org; Wed, 07 Jun 2023 14:19:50 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1686161988; 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=wGVtEoqBAl8lwptyFmXJk6BJGB0qFKkr4ZFuvw51r0Q=; b=AqedxIuQfcyxM5GX6psV3tj+WPmSvpj8PMHb1LJQkK0Hzh8bc33y4i/8XWfu0EH68JvyhW qO1nib+vIDm/ui8gdhearcgZ9uyvEIv9N/6pHVM+qLmjMixOOpwxeCLbL1r/zWRjNs0pdH SwAS+iPJcCQR4NSaVlkt1oMqrJVzso0= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-540-M9_KrGU4O_etW2pFzX5xUw-1; Wed, 07 Jun 2023 14:19:44 -0400 X-MC-Unique: M9_KrGU4O_etW2pFzX5xUw-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id ED5C33802138; Wed, 7 Jun 2023 18:19:43 +0000 (UTC) Received: from localhost (unknown [10.39.192.9]) by smtp.corp.redhat.com (Postfix) with ESMTP id 6CBC81121314; Wed, 7 Jun 2023 18:19:43 +0000 (UTC) Date: Wed, 7 Jun 2023 14:19:41 -0400 From: Stefan Hajnoczi To: Kevin Wolf Cc: qemu-block@nongnu.org, hreitz@redhat.com, eblake@redhat.com, qemu-devel@nongnu.org Subject: Re: [PATCH v2 00/11] block: Re-enable the graph lock Message-ID: <20230607181941.GH2138915@fedora> References: <20230605085711.21261-1-kwolf@redhat.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="G0B+TaaRmkzvaMsb" Content-Disposition: inline In-Reply-To: <20230605085711.21261-1-kwolf@redhat.com> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.3 Received-SPF: pass client-ip=170.10.133.124; envelope-from=stefanha@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, 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, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org --G0B+TaaRmkzvaMsb Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Jun 05, 2023 at 10:57:00AM +0200, Kevin Wolf wrote: > This series fixes the deadlock that was observed before commit ad128dff > ('graph-lock: Disable locking for now'), which just disabled the graph > lock completely as a workaround to get 8.0.1 stable. >=20 > In theory the problem is simple: We can't poll while still holding the > lock of a different AioContext. So bdrv_graph_wrlock() just needs to > drop that lock before it polls. However, there are a number of callers > that don't even hold the AioContext lock they are supposed to hold, so > temporarily unlocking tries to unlock a mutex that isn't locked, > resulting in assertion failures. >=20 > Therefore, much of this series is just for fixing AioContext locking > correctness. It is only the last two patches that actually fix the > deadlock and reenable the graph locking. >=20 > v2: > - Fixed patch 2 to actually lock the correct AioContext even if the > device doesn't support iothreads > - Improved the commit message for patch 7 [Eric] > - Fixed mismerge in patch 11 (v1 incorrectly left an #if 0 around) >=20 > Kevin Wolf (11): > iotests: Test active commit with iothread and background I/O > qdev-properties-system: Lock AioContext for blk_insert_bs() > test-block-iothread: Lock AioContext for blk_insert_bs() > block: Fix AioContext locking in bdrv_open_child() > block: Fix AioContext locking in bdrv_attach_child_common() > block: Fix AioContext locking in bdrv_reopen_parse_file_or_backing() > block: Fix AioContext locking in bdrv_open_inherit() > block: Fix AioContext locking in bdrv_open_backing_file() > blockjob: Fix AioContext locking in block_job_add_bdrv() > graph-lock: Unlock the AioContext while polling > Revert "graph-lock: Disable locking for now" >=20 > include/block/graph-lock.h | 6 +- > block.c | 103 ++++++++++++++++-- > block/graph-lock.c | 42 ++++--- > blockjob.c | 17 ++- > hw/core/qdev-properties-system.c | 8 +- > tests/unit/test-block-iothread.c | 7 +- > .../tests/iothreads-commit-active | 85 +++++++++++++++ > .../tests/iothreads-commit-active.out | 23 ++++ > 8 files changed, 250 insertions(+), 41 deletions(-) > create mode 100755 tests/qemu-iotests/tests/iothreads-commit-active > create mode 100644 tests/qemu-iotests/tests/iothreads-commit-active.out >=20 > --=20 > 2.40.1 >=20 Reviewed-by: Stefan Hajnoczi --G0B+TaaRmkzvaMsb Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEhpWov9P5fNqsNXdanKSrs4Grc8gFAmSAyj0ACgkQnKSrs4Gr c8jS0AgAwDBhT+DO0ipY1k/RRdcAohljk2ITacM1aN101RH5nksVvmEaKHE3tJXW 96BTVp/uBzqwQuzRltSLTPjWa6ZpWLNH0TV6nl6iIRXQrJWDEIsfhae/FQ5PYULi YAYr5Ehz6vUwaLNgG79taFcSK6n+5ZaBaKFp6S9BjaPVtcly9sFtA9Gns3jMw9Rp vtrA/hYCVGykJ4ykO4jXRx2Q4fxVN5nj0etvoULubWrhoZfTgWuCXN/yX+D2agaw AZifX7BbCUz+Etf+iqK+h+SfVqsi0qBonGXDFeah3fIo674vulKqHqIPncu8Dcp6 Hx/O9/tuIgB9qkWrOQIYBPtTnJGATw== =Xzta -----END PGP SIGNATURE----- --G0B+TaaRmkzvaMsb--