From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Vrabel Subject: Re: [Xen-devel] [PATCHv2 net-next] xen-netback: fix race between napi_complete() and interrupt handler Date: Fri, 16 May 2014 10:53:59 +0100 Message-ID: <5375E037.1050103@citrix.com> References: <1400174228-16572-1-git-send-email-david.vrabel@citrix.com> <1400229009.883.37.camel@kazak.uk.xensource.com> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Cc: , Wei Liu , To: Ian Campbell , David Vrabel Return-path: Received: from smtp02.citrix.com ([66.165.176.63]:14132 "EHLO SMTP02.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756702AbaEPJyB (ORCPT ); Fri, 16 May 2014 05:54:01 -0400 In-Reply-To: <1400229009.883.37.camel@kazak.uk.xensource.com> Sender: netdev-owner@vger.kernel.org List-ID: On 16/05/14 09:30, Ian Campbell wrote: > On Thu, 2014-05-15 at 18:17 +0100, David Vrabel wrote: >> When the NAPI budget was not all used, xenvif_poll() would call >> napi_complete() /after/ enabling the interrupt. This resulted in a >> race between the napi_complete() and the napi_schedule() in the >> interrupt handler. The use of local_irq_save/restore() avoided by >> race iff the handler is running on the same CPU but not if it was >> running on a different CPU. >> >> Fix this properly by calling napi_complete() before reenabling >> interrupts (in the xenvif_napi_schedule_or_enable_irq() call). >> >> Signed-off-by: David Vrabel >> --- >> v2: >> - Rename xenvif_check_rx_xenvif() to >> xenvif_napi_schedule_or_enable_irq() to make it more obvious what it >> does. > > Which is to update the event pointer such that IRQs are generated again > rather than enabling IRQs as such (enable_irq makes me think of > EFLAGS.IF). But given that I can't think of a better way to describe it: > Acked-by: Ian Campbell Would xenvif_napi_schedule_or_enable_event() be better? David