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 16730CD4F2C for ; Thu, 13 Nov 2025 01:19:35 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1vJLyK-0004dQ-Ny; Wed, 12 Nov 2025 20:18:00 -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 1vJLxP-0002iy-HQ for qemu-devel@nongnu.org; Wed, 12 Nov 2025 20:17:03 -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 1vJLxM-0005rp-SM for qemu-devel@nongnu.org; Wed, 12 Nov 2025 20:17:02 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1762996620; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=4B12cEQrDwPWjzA13TdS34zZbWrTYxvI42/uYIj4SNY=; b=PDq00vXForPGLHftBh8Os5pTPq9mRQidxvue2zAJFai5gtilYd4KM5WcSqNTh5flAyWBMf kg+p1txwThIH4KeOtxg8iqT5u9gaPcz3egydSBBv3iHKny9flHpmGQ7Zx7SHJaplCjk6Fj wRnKKlzBbl/oRFkWc3trQ+p8QytZL6A= Received: from mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-478-H6WUqjoOOK-SfyKbDLtJvg-1; Wed, 12 Nov 2025 20:16:58 -0500 X-MC-Unique: H6WUqjoOOK-SfyKbDLtJvg-1 X-Mimecast-MFC-AGG-ID: H6WUqjoOOK-SfyKbDLtJvg_1762996617 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (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-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id A63631800452; Thu, 13 Nov 2025 01:16:56 +0000 (UTC) Received: from green.redhat.com (unknown [10.2.16.87]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id DEBEF180049F; Thu, 13 Nov 2025 01:16:54 +0000 (UTC) From: Eric Blake To: qemu-devel@nongnu.org Cc: qemu-block@nongnu.org, kwolf@redhat.com, berrange@redhat.com, Vladimir Sementsov-Ogievskiy , Hanna Reitz Subject: [PATCH v3 12/13] nbd: Avoid deadlock in client connecting to same-process server Date: Wed, 12 Nov 2025 19:11:37 -0600 Message-ID: <20251113011625.878876-27-eblake@redhat.com> In-Reply-To: <20251113011625.878876-15-eblake@redhat.com> References: <20251113011625.878876-15-eblake@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 Received-SPF: pass client-ip=170.10.133.124; envelope-from=eblake@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, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_PASS=-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 See the previous patch for a longer description of the deadlock. Now that QIONetListener supports waiting for clients in the main loop AioContext, NBD can use that to ensure that the server can make progress even when a client is intentionally starving the GMainContext from any activity not tied to an AioContext. Note that command-line arguments and QMP commands like nbd-server-start or nbd-server-stop that manipulate whether the NBD server exists are serviced in the main loop; and therefore, this patch does not fall foul of the restrictions in the previous patch about the inherent unsafe race possible if a QIONetListener can have its async callback modified by a different thread than the one servicing polls. Fixes: https://gitlab.com/qemu-project/qemu/-/issues/3169 Signed-off-by: Eric Blake Reviewed-by: Daniel P. Berrangé --- v2: new patch v3: enhance commit message --- blockdev-nbd.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/blockdev-nbd.c b/blockdev-nbd.c index 1e3e634b87d..696474aea93 100644 --- a/blockdev-nbd.c +++ b/blockdev-nbd.c @@ -94,10 +94,10 @@ static void nbd_update_server_watch(NBDServerData *s) { if (s->listener) { if (!s->max_connections || s->connections < s->max_connections) { - qio_net_listener_set_client_func(s->listener, nbd_accept, NULL, + qio_net_listener_set_client_aio_func(s->listener, nbd_accept, NULL, NULL); } else { - qio_net_listener_set_client_func(s->listener, NULL, NULL, NULL); + qio_net_listener_set_client_aio_func(s->listener, NULL, NULL, NULL); } } } -- 2.51.1