From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wei Liu Subject: Re: [PATCHv1 net] xen-netback: release pending index before pushing Tx responses Date: Tue, 24 Feb 2015 12:03:24 +0000 Message-ID: <20150224120324.GH20083@zion.uk.xensource.com> References: <1424776679-7509-1-git-send-email-david.vrabel@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Cc: , , Ian Campbell , Wei Liu To: David Vrabel Return-path: Received: from smtp.citrix.com ([66.165.176.89]:5164 "EHLO SMTP.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752135AbbBXMD0 (ORCPT ); Tue, 24 Feb 2015 07:03:26 -0500 Content-Disposition: inline In-Reply-To: <1424776679-7509-1-git-send-email-david.vrabel@citrix.com> Sender: netdev-owner@vger.kernel.org List-ID: On Tue, Feb 24, 2015 at 11:17:59AM +0000, David Vrabel wrote: > If the pending indexes are released /after/ pushing the Tx response > then a stale pending index may be used if a new Tx request is > immediately pushed by the frontend. The may cause various WARNINGs or > BUGs if the stale pending index is actually still in use. > > Fix this by releasing the pending index before pushing the Tx > response. > > The full barrier for the pending ring update is not required since the > the Tx response push already has a suitable write barrier. > > Signed-off-by: David Vrabel Reviewed-by: Wei Liu