From patchwork Thu Feb 9 13:01:09 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Gerd Hoffmann X-Patchwork-Id: 9564531 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 2FC47601C3 for ; Thu, 9 Feb 2017 13:15:09 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 18645284E7 for ; Thu, 9 Feb 2017 13:15:09 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 0D05228517; Thu, 9 Feb 2017 13:15:09 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 69FE8284E7 for ; Thu, 9 Feb 2017 13:15:07 +0000 (UTC) Received: from localhost ([::1]:37838 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cboZ0-0003Pi-Hi for patchwork-qemu-devel@patchwork.kernel.org; Thu, 09 Feb 2017 08:15:06 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:34067) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cboMF-0000Pf-G3 for qemu-devel@nongnu.org; Thu, 09 Feb 2017 08:01:56 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cboME-00029l-Hu for qemu-devel@nongnu.org; Thu, 09 Feb 2017 08:01:55 -0500 Received: from mx1.redhat.com ([209.132.183.28]:49388) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1cboME-00029O-AB; Thu, 09 Feb 2017 08:01:54 -0500 Received: from smtp.corp.redhat.com (int-mx16.intmail.prod.int.phx2.redhat.com [10.5.11.28]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 5FEC0C01B149; Thu, 9 Feb 2017 13:01:54 +0000 (UTC) Received: from nilsson.home.kraxel.org (ovpn-117-196.ams2.redhat.com [10.36.117.196]) by smtp.corp.redhat.com (Postfix) with ESMTP id EE9C06377B; Thu, 9 Feb 2017 13:01:51 +0000 (UTC) Received: by nilsson.home.kraxel.org (Postfix, from userid 500) id 7CCE480D46; Thu, 9 Feb 2017 14:01:19 +0100 (CET) From: Gerd Hoffmann To: qemu-devel@nongnu.org Date: Thu, 9 Feb 2017 14:01:09 +0100 Message-Id: <1486645277-4724-3-git-send-email-kraxel@redhat.com> In-Reply-To: <1486645277-4724-1-git-send-email-kraxel@redhat.com> References: <1486645277-4724-1-git-send-email-kraxel@redhat.com> X-Scanned-By: MIMEDefang 2.74 on 10.5.11.28 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.31]); Thu, 09 Feb 2017 13:01:54 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 209.132.183.28 Subject: [Qemu-devel] [PULL 02/10] vnc: do not disconnect on EAGAIN X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Michael Tokarev , Gerd Hoffmann , qemu-stable@nongnu.org Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" X-Virus-Scanned: ClamAV using ClamSMTP From: Michael Tokarev When qemu vnc server is trying to send large update to clients, there might be a situation when system responds with something like EAGAIN, indicating that there's no system memory to send that much data (depending on the network speed, client and server and what is happening). In this case, something like this happens on qemu side (from strace): sendmsg(16, {msg_name(0)=NULL, msg_iov(1)=[{"\244\"..., 729186}], msg_controllen=0, msg_flags=0}, 0) = 103950 sendmsg(16, {msg_name(0)=NULL, msg_iov(1)=[{"lz\346"..., 1559618}], msg_controllen=0, msg_flags=0}, 0) = -1 EAGAIN sendmsg(-1, {msg_name(0)=NULL, msg_iov(1)=[{"lz\346"..., 1559618}], msg_controllen=0, msg_flags=0}, 0) = -1 EBADF qemu closes the socket before the retry, and obviously it gets EBADF when trying to send to -1. This is because there WAS a special handling for EAGAIN, but now it doesn't work anymore, after commit 04d2529da27db512dcbd5e99d0e26d333f16efcc, because now in all error-like cases we initiate vnc disconnect. This change were introduced in qemu 2.6, and caused numerous grief for many people, resulting in their vnc clients reporting sporadic random disconnects from vnc server. Fix that by doing the disconnect only when necessary, i.e. omitting this very case of EAGAIN. Hopefully the existing condition (comparing with QIO_CHANNEL_ERR_BLOCK) is sufficient, as the original code (before the above commit) were checking for other errno values too. Apparently there's another (semi?)bug exist somewhere here, since the code tries to write to fd# -1, it probably should check if the connection is open before. But this isn't important. Signed-off-by: Michael Tokarev Reviewed-by: Daniel P. Berrange Message-id: 1486115549-9398-1-git-send-email-mjt@msgid.tls.msk.ru Fixes: 04d2529da27db512dcbd5e99d0e26d333f16efcc Cc: Daniel P. Berrange Cc: Gerd Hoffmann Cc: qemu-stable@nongnu.org Signed-off-by: Gerd Hoffmann --- ui/vnc.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/ui/vnc.c b/ui/vnc.c index cdeb79c..f2701e5 100644 --- a/ui/vnc.c +++ b/ui/vnc.c @@ -1256,12 +1256,13 @@ ssize_t vnc_client_io_error(VncState *vs, ssize_t ret, Error **errp) if (ret <= 0) { if (ret == 0) { VNC_DEBUG("Closing down client sock: EOF\n"); + vnc_disconnect_start(vs); } else if (ret != QIO_CHANNEL_ERR_BLOCK) { VNC_DEBUG("Closing down client sock: ret %zd (%s)\n", ret, errp ? error_get_pretty(*errp) : "Unknown"); + vnc_disconnect_start(vs); } - vnc_disconnect_start(vs); if (errp) { error_free(*errp); *errp = NULL;