From patchwork Wed Nov 15 17:20:09 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kevin Wolf X-Patchwork-Id: 13457126 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 5A0B8C54FB9 for ; Wed, 15 Nov 2023 17:21:50 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1r3JZ1-0007e0-0n; Wed, 15 Nov 2023 12:20:31 -0500 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 1r3JZ0-0007dl-A4 for qemu-devel@nongnu.org; Wed, 15 Nov 2023 12:20:30 -0500 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 1r3JYy-0003CL-Q4 for qemu-devel@nongnu.org; Wed, 15 Nov 2023 12:20:30 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1700068828; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=70hLchKKDMD2HpZFpzNZq73fWIcmHKXu1vjidAtQ9QA=; b=Ar0BblzNwQuDCg+Yiaup88aFtMovxRWCqvceauJTLbRHIMewfIelUo6oKRTGkLl8d9H2kY VDR3lXUI6WGRZaY9Yhyfawm6/AMG8BVgCh1DJve7g6kJW/NRKvphxicdNb5hDtHwspJbP1 tlF6NB1PMICYwf89kSBonmt9AMMk7ko= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-502-ctUyZJtqPximIYwcBk0V_w-1; Wed, 15 Nov 2023 12:20:26 -0500 X-MC-Unique: ctUyZJtqPximIYwcBk0V_w-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.rdu2.redhat.com [10.11.54.1]) (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 mimecast-mx02.redhat.com (Postfix) with ESMTPS id EBC96185A7AD; Wed, 15 Nov 2023 17:20:19 +0000 (UTC) Received: from merkur.fritz.box (unknown [10.39.194.188]) by smtp.corp.redhat.com (Postfix) with ESMTP id 1E3FE36E; Wed, 15 Nov 2023 17:20:19 +0000 (UTC) From: Kevin Wolf To: qemu-block@nongnu.org Cc: kwolf@redhat.com, hreitz@redhat.com, stefanha@redhat.com, qemu-devel@nongnu.org Subject: [PATCH for-8.2 1/4] block: Fix bdrv_graph_wrlock() call in blk_remove_bs() Date: Wed, 15 Nov 2023 18:20:09 +0100 Message-ID: <20231115172012.112727-2-kwolf@redhat.com> In-Reply-To: <20231115172012.112727-1-kwolf@redhat.com> References: <20231115172012.112727-1-kwolf@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.1 Received-SPF: pass client-ip=170.10.133.124; envelope-from=kwolf@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.099, 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_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, 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 While not all callers of blk_remove_bs() are correct in this respect, the assumption in the function is that callers hold the AioContext lock of the BlockBackend (this is required by the drain calls in it). In order to avoid deadlock in the nested event loop, bdrv_graph_wrlock() has then to be called with the root BlockDriverState as its parameter instead of NULL, so that this AioContext lock is temporarily dropped. Fixes: https://issues.redhat.com/browse/RHEL-1761 Signed-off-by: Kevin Wolf --- block/block-backend.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/block/block-backend.c b/block/block-backend.c index 4053134781..f6f05ead28 100644 --- a/block/block-backend.c +++ b/block/block-backend.c @@ -882,6 +882,8 @@ BlockBackend *blk_by_public(BlockBackendPublic *public) /* * Disassociates the currently associated BlockDriverState from @blk. + * + * The caller must hold the AioContext lock for the BlockBackend. */ void blk_remove_bs(BlockBackend *blk) { @@ -916,7 +918,7 @@ void blk_remove_bs(BlockBackend *blk) root = blk->root; blk->root = NULL; - bdrv_graph_wrlock(NULL); + bdrv_graph_wrlock(root->bs); bdrv_root_unref_child(root); bdrv_graph_wrunlock(); }