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 3EFF1C54F30 for ; Tue, 27 May 2025 15:13:05 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1uJvyf-0003hP-DV; Tue, 27 May 2025 11:12:29 -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 1uJvyd-0003gb-MM for qemu-devel@nongnu.org; Tue, 27 May 2025 11:12:27 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1uJvya-0007Wg-2l for qemu-devel@nongnu.org; Tue, 27 May 2025 11:12:27 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1748358742; 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=y5/MjKW2RSK2RfT7kIJyxwxdk910yYMl/AleLTjg/9Q=; b=cUDONCAxCFokdnQzOI6MKmzGxlzPwSp4sPm6xsXoLb4Votvt41K4JiqnTWltfPXoclIxq2 fEKYS7vu+f7rtH1rBS0xER1IKazUWHqVp+HSSVstGj6z7uKmzUEQO3SR9h87iKdJOz4akI hMkX4UMRT0c9n1RN3BQ19Z0oqC90vL4= Received: from mx-prod-mc-04.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-235-3ZPULxalNuS2I2hVMf919w-1; Tue, 27 May 2025 11:12:18 -0400 X-MC-Unique: 3ZPULxalNuS2I2hVMf919w-1 X-Mimecast-MFC-AGG-ID: 3ZPULxalNuS2I2hVMf919w_1748358733 Received: from mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.4]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id BACAC194510A; Tue, 27 May 2025 15:12:12 +0000 (UTC) Received: from redhat.com (unknown [10.44.34.20]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 1599330001B0; Tue, 27 May 2025 15:12:06 +0000 (UTC) Date: Tue, 27 May 2025 17:12:04 +0200 From: Kevin Wolf To: Fiona Ebner Cc: qemu-block@nongnu.org, qemu-devel@nongnu.org, den@virtuozzo.com, andrey.drobyshev@virtuozzo.com, hreitz@redhat.com, stefanha@redhat.com, eblake@redhat.com, jsnow@redhat.com, vsementsov@yandex-team.ru, xiechanglong.d@gmail.com, wencongyang2@huawei.com, berto@igalia.com, fam@euphon.net, ari@tuxera.com Subject: Re: [PATCH v3 09/24] block: move drain outside of bdrv_try_change_aio_context() Message-ID: References: <20250526132140.1641377-1-f.ebner@proxmox.com> <20250526132140.1641377-10-f.ebner@proxmox.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250526132140.1641377-10-f.ebner@proxmox.com> X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 Received-SPF: pass client-ip=170.10.129.124; envelope-from=kwolf@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -49 X-Spam_score: -5.0 X-Spam_bar: ----- X-Spam_report: (-5.0 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-2.907, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 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 Am 26.05.2025 um 15:21 hat Fiona Ebner geschrieben: > This is part of resolving the deadlock mentioned in commit "block: > move draining out of bdrv_change_aio_context() and mark GRAPH_RDLOCK". > > Convert the function to a _locked() version that has to be called with > the graph lock held and add a convenience wrapper that has to be > called with the graph unlocked, which drains and takes the lock > itself. Since bdrv_try_change_aio_context() is global state code, the > wrapper is too. > > Callers are adapted to use the appropriate variant, depending on > whether the caller already holds the lock. In the > test_set_aio_context() unit test, prior drains can be removed, because > draining already happens inside the new wrapper. > > Note that bdrv_attach_child_common_abort(), bdrv_attach_child_common() > and bdrv_root_unref_child() hold the graph lock and are not actually > allowed to drain either. This will be addressed in the following > commits. > > Functions like qmp_blockdev_mirror() query the nodes to act on before > draining and locking. In theory, draining could invalidate those nodes. > This kind of issue is not addressed by these commits. > > Signed-off-by: Fiona Ebner Reviewed-by: Kevin Wolf