From patchwork Tue Oct 31 18:59:02 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kevin Wolf X-Patchwork-Id: 1857732 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@legolas.ozlabs.org Authentication-Results: legolas.ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=Hua0SdeO; dkim-atps=neutral Authentication-Results: legolas.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org (client-ip=209.51.188.17; helo=lists.gnu.org; envelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org; receiver=patchwork.ozlabs.org) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-ECDSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by legolas.ozlabs.org (Postfix) with ESMTPS id 4SKfjL23Lfz1yQ6 for ; Wed, 1 Nov 2023 06:05:26 +1100 (AEDT) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qxtyX-0004Q0-Pd; Tue, 31 Oct 2023 15:00:29 -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 1qxtyA-0004Ck-BI for qemu-devel@nongnu.org; Tue, 31 Oct 2023 15:00:09 -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 1qxtxm-00068u-Bo for qemu-devel@nongnu.org; Tue, 31 Oct 2023 15:00:03 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1698778781; 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=lpinoL1G2q5CE1NDLmmev9agQismCJOSxfaHubnK3hY=; b=Hua0SdeO1GEYjZtsaNURUCdT1ejaQ+7MkR1N/n1f9jEaE6H01dVPgsr6D4Un9Y9UpABswQ rc3UCMwlX49bpJPj2HxSaQCnlVSHDUtf1Xba8cUpihdbUtK2WHNUAz7t9UPhOebUpb4Te1 gZyY4r9FvMze5R/S9hWdcxkV2DrqBZA= 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-645-B09XwH2WNIKdNmSelFPqRQ-1; Tue, 31 Oct 2023 14:59:29 -0400 X-MC-Unique: B09XwH2WNIKdNmSelFPqRQ-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 9872A185A78F; Tue, 31 Oct 2023 18:59:29 +0000 (UTC) Received: from merkur.fritz.box (unknown [10.39.194.218]) by smtp.corp.redhat.com (Postfix) with ESMTP id 0882B25C0; Tue, 31 Oct 2023 18:59:28 +0000 (UTC) From: Kevin Wolf To: qemu-block@nongnu.org Cc: kwolf@redhat.com, qemu-devel@nongnu.org Subject: [PULL 11/27] blockjob: drop AioContext lock before calling bdrv_graph_wrlock() Date: Tue, 31 Oct 2023 19:59:02 +0100 Message-ID: <20231031185918.346940-12-kwolf@redhat.com> In-Reply-To: <20231031185918.346940-1-kwolf@redhat.com> References: <20231031185918.346940-1-kwolf@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.1 Received-SPF: pass client-ip=170.10.129.124; envelope-from=kwolf@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -25 X-Spam_score: -2.6 X-Spam_bar: -- X-Spam_report: (-2.6 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.481, 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_H4=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+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org From: Fiona Ebner Same rationale as in 31b2ddfea3 ("graph-lock: Unlock the AioContext while polling"). Otherwise, a deadlock can happen. The alternative would be to pass a BlockDriverState along to bdrv_graph_wrlock(), but there is no BlockDriverState readily available and it's also better conceptually, because the lock is held for the job. The function is always called with the job's AioContext lock held, via one of the .abort, .clean, .free or .prepare job driver functions. Thus, it's safe to drop it. While mirror_exit_common() does hold a second AioContext lock while calling block_job_remove_all_bdrv(), that is for the main thread's AioContext and does not need to be dropped (bdrv_graph_wrlock(bs) also skips dropping the lock if bdrv_get_aio_context(bs) == qemu_get_aio_context()). Suggested-by: Paolo Bonzini Signed-off-by: Fiona Ebner Message-ID: <20231019131936.414246-2-f.ebner@proxmox.com> Reviewed-by: Kevin Wolf Signed-off-by: Kevin Wolf --- blockjob.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/blockjob.c b/blockjob.c index 807f992b59..953dc1b6dc 100644 --- a/blockjob.c +++ b/blockjob.c @@ -198,7 +198,9 @@ void block_job_remove_all_bdrv(BlockJob *job) * one to make sure that such a concurrent access does not attempt * to process an already freed BdrvChild. */ + aio_context_release(job->job.aio_context); bdrv_graph_wrlock(NULL); + aio_context_acquire(job->job.aio_context); while (job->nodes) { GSList *l = job->nodes; BdrvChild *c = l->data;