From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Gallatin Subject: Re: [RFC] net: napi fix Date: Thu, 13 Dec 2007 09:13:54 -0500 Message-ID: <47613E22.6060705@myri.com> References: <47601A73.5010804@myri.com> <20071212.093819.205755031.davem@davemloft.net> <47602B77.2090202@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: "Kok, Auke" , David Miller , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, jgarzik@pobox.com, shemminger@linux-foundation.org, Jesse Brandeburg To: Joonwoo Park Return-path: Received: from mailbox2.myri.com ([64.172.73.26]:1955 "EHLO myri.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754768AbXLMOTp (ORCPT ); Thu, 13 Dec 2007 09:19:45 -0500 In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: Joonwoo Park wrote: > 2007/12/13, Kok, Auke : >> David Miller wrote: >>> From: Andrew Gallatin >>> Date: Wed, 12 Dec 2007 12:29:23 -0500 >>> >>>> Is the netif_running() check even required? >>> No, it is not. >>> >>> When a device is brought down, one of the first things >>> that happens is that we wait for all pending NAPI polls >>> to complete, then block any new polls from starting. >> I think this was previously (pre-2.6.24) not the case, which is why e1000 et al >> has this check as well and that's exactly what is causing most of the >> net_rx_action oopses in the first place. Without the netif_running() check >> previously the drivers were just unusable with NAPI and prone to many races with >> down (i.e. touching some ethtool ioctl which wants to do a reset while routing >> small packets at high numbers). that's why we added the netif_running() check in >> the first place :) >> >> There might be more drivers lurking that need this change... >> >> Auke >> > > Also in my case, without netif_running() check, I cannot do ifconfig down. > It stucked if packet generator was sending packets. If the netif_running() check is indeed required to make a device break out of napi polling and respond to an ifconfig down, then I think the netif_running() check should be moved up into net_rx_action() to avoid potential for driver complexity and bugs like the ones you found. Drew