From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751535AbaAOKhZ (ORCPT ); Wed, 15 Jan 2014 05:37:25 -0500 Received: from smtp.citrix.com ([66.165.176.89]:48773 "EHLO SMTP.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751010AbaAOKhX (ORCPT ); Wed, 15 Jan 2014 05:37:23 -0500 X-IronPort-AV: E=Sophos;i="4.95,662,1384300800"; d="scan'208";a="93031440" Date: Wed, 15 Jan 2014 10:37:07 +0000 From: Wei Liu To: Zoltan Kiss CC: , , , , , Subject: Re: [PATCH net-next] xen-netback: Rework rx_work_todo Message-ID: <20140115103707.GI5698@zion.uk.xensource.com> References: <1389727719-21439-1-git-send-email-zoltan.kiss@citrix.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <1389727719-21439-1-git-send-email-zoltan.kiss@citrix.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-DLP: MIA2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jan 14, 2014 at 07:28:39PM +0000, Zoltan Kiss wrote: > The recent patch to fix receive side flow control (11b57f) solved the spinning > thread problem, however caused an another one. The receive side can stall, if: > - xenvif_rx_action sets rx_queue_stopped to false > - interrupt happens, and sets rx_event to true > - then xenvif_kthread sets rx_event to false > If you mean "rx_work_todo" returns false. In this case (!skb_queue_empty(&vif->rx_queue) && !vif->rx_queue_stopped) || vif->rx_event; can still be true, can't it? > Also, through rx_event a malicious guest can force the RX thread to spin. This > patch ditch that two variable, and rework rx_work_todo. If the thread finds it This seems to be a bigger problem. Can you elaborate? Wei.