From patchwork Thu Feb 2 14:26:29 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: "Denis V. Lunev" X-Patchwork-Id: 9551975 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 692C460236 for ; Thu, 2 Feb 2017 14:27:02 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 46AC528408 for ; Thu, 2 Feb 2017 14:27:02 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 3B2B728440; Thu, 2 Feb 2017 14:27:02 +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 B1CE028408 for ; Thu, 2 Feb 2017 14:27:01 +0000 (UTC) Received: from localhost ([::1]:56945 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cZILk-0000sQ-F2 for patchwork-qemu-devel@patchwork.kernel.org; Thu, 02 Feb 2017 09:27:00 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:32829) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cZILK-0000gM-GV for qemu-devel@nongnu.org; Thu, 02 Feb 2017 09:26:39 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cZILH-0001sB-A9 for qemu-devel@nongnu.org; Thu, 02 Feb 2017 09:26:34 -0500 Received: from mailhub.sw.ru ([195.214.232.25]:1512 helo=relay.sw.ru) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1cZILG-0001ri-Ug for qemu-devel@nongnu.org; Thu, 02 Feb 2017 09:26:31 -0500 Received: from iris.sw.ru (msk-vpn.virtuozzo.com [195.214.232.6]) by relay.sw.ru (8.13.4/8.13.4) with ESMTP id v12EQTZS007594; Thu, 2 Feb 2017 17:26:29 +0300 (MSK) From: "Denis V. Lunev" To: qemu-devel@nongnu.org Date: Thu, 2 Feb 2017 17:26:29 +0300 Message-Id: <1486045589-8074-1-git-send-email-den@openvz.org> X-Mailer: git-send-email 2.7.4 MIME-Version: 1.0 X-MIME-Autoconverted: from 8bit to quoted-printable by relay.sw.ru id v12EQTZS007594 X-detected-operating-system: by eggs.gnu.org: OpenBSD 3.x [fuzzy] X-Received-From: 195.214.232.25 Subject: [Qemu-devel] [PATCH v3 1/1] qemu-char: socket backend: disconnect on write error 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: "Denis V . Lunev" , Anton Nefedov , =?UTF-8?q?Marc-Andr=C3=A9=20Lureau?= , Paolo Bonzini Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" X-Virus-Scanned: ClamAV using ClamSMTP From: Anton Nefedov Socket backend read handler should normally perform a disconnect, however the read handler may not get a chance to run if the frontend is not ready (qemu_chr_be_can_write() == 0). This means that in virtio-serial frontend case if - the host has disconnected (giving EPIPE on socket write) - and the guest has disconnected (-> frontend not ready -> backend will not read) - and there is still data (frontend->backend) to flush (has to be a really tricky timing but nevertheless, we have observed the case in production) This results in virtio-serial trying to flush this data continiously forming a busy loop. Solution: react on write error in the socket write handler. errno is not reliable after qio_channel_writev_full(), so we may not get the exact EPIPE, so disconnect on any error but QIO_CHANNEL_ERR_BLOCK which io_channel_send_full() converts to errno EAGAIN. We must not disconnect right away though, there still may be data to read (see 4bf1cb0). Signed-off-by: Anton Nefedov Signed-off-by: Denis V. Lunev CC: Paolo Bonzini CC: Daniel P. Berrange CC: Marc-André Lureau --- Changes from v2: - fixed prototype of tcp_chr_disconnect Changes from v1: - we do not rely on EPIPE anynore. Socket should be closed on all errors except EAGAIN chardev/char-socket.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/chardev/char-socket.c b/chardev/char-socket.c index 4068dc5..865c527 100644 --- a/chardev/char-socket.c +++ b/chardev/char-socket.c @@ -97,6 +97,9 @@ static gboolean tcp_chr_accept(QIOChannel *chan, GIOCondition cond, void *opaque); +static int tcp_chr_read_poll(void *opaque); +static void tcp_chr_disconnect(Chardev *chr); + /* Called with chr_write_lock held. */ static int tcp_chr_write(Chardev *chr, const uint8_t *buf, int len) { @@ -114,6 +117,13 @@ static int tcp_chr_write(Chardev *chr, const uint8_t *buf, int len) s->write_msgfds_num = 0; } + if (ret < 0 && errno != EAGAIN) { + if (tcp_chr_read_poll(chr) <= 0) { + tcp_chr_disconnect(chr); + return len; + } /* else let the read handler finish it properly */ + } + return ret; } else { /* XXX: indicate an error ? */