From patchwork Thu Oct 19 13:19:35 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Fiona Ebner X-Patchwork-Id: 13429165 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 EB5ABCDB482 for ; Thu, 19 Oct 2023 13:22:20 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qtSy4-0005ks-BX; Thu, 19 Oct 2023 09:21:42 -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 1qtSwQ-0004UI-9f; Thu, 19 Oct 2023 09:20:05 -0400 Received: from proxmox-new.maurer-it.com ([94.136.29.106]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qtSwM-0004Gc-Vt; Thu, 19 Oct 2023 09:19:58 -0400 Received: from proxmox-new.maurer-it.com (localhost.localdomain [127.0.0.1]) by proxmox-new.maurer-it.com (Proxmox) with ESMTP id 4047E430E7; Thu, 19 Oct 2023 15:19:41 +0200 (CEST) From: Fiona Ebner To: qemu-devel@nongnu.org Cc: qemu-block@nongnu.org, vsementsov@yandex-team.ru, jsnow@redhat.com, hreitz@redhat.com, kwolf@redhat.com, pbonzini@redhat.com, t.lamprecht@proxmox.com Subject: [PATCH 2/3] block: avoid potential deadlock during bdrv_graph_wrlock() in bdrv_close() Date: Thu, 19 Oct 2023 15:19:35 +0200 Message-Id: <20231019131936.414246-3-f.ebner@proxmox.com> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20231019131936.414246-1-f.ebner@proxmox.com> References: <20231019131936.414246-1-f.ebner@proxmox.com> MIME-Version: 1.0 Received-SPF: pass client-ip=94.136.29.106; envelope-from=f.ebner@proxmox.com; helo=proxmox-new.maurer-it.com X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, 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 by passing the BlockDriverState along, so the held AioContext can be dropped before polling. See commit 31b2ddfea3 ("graph-lock: Unlock the AioContext while polling") which introduced this functionality for more information. The only way to reach bdrv_close() is via bdrv_unref() and for calling that the BlockDriverState's AioContext lock is supposed to be held. Signed-off-by: Fiona Ebner --- Is it safe to expect callers of bdrv_unref() to hold the appropriate AioContext lock? block.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/block.c b/block.c index f9cf05ddcf..a527aa1a4c 100644 --- a/block.c +++ b/block.c @@ -5200,7 +5200,7 @@ static void bdrv_close(BlockDriverState *bs) bs->drv = NULL; } - bdrv_graph_wrlock(NULL); + bdrv_graph_wrlock(bs); QLIST_FOREACH_SAFE(child, &bs->children, next, next) { bdrv_unref_child(bs, child); }