From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anton Vorontsov Subject: Re: [PATCH RFC] gianfar: Make polling safe with IRQs disabled Date: Mon, 9 Nov 2009 16:32:31 +0300 Message-ID: <20091109133231.GA26965@oksana.dev.rtsoft.ru> References: <20091104225711.GA30844@oksana.dev.rtsoft.ru> <20091108.010533.212571001.davem@davemloft.net> Reply-To: avorontsov@ru.mvista.com Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Cc: afleming@freescale.com, jason.wessel@windriver.com, netdev@vger.kernel.org, linuxppc-dev@ozlabs.org To: David Miller Return-path: Received: from imap.ru.mvista.com ([213.79.90.228]:14855 "EHLO buildserver.ru.mvista.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1755713AbZKINc1 (ORCPT ); Mon, 9 Nov 2009 08:32:27 -0500 Content-Disposition: inline In-Reply-To: <20091108.010533.212571001.davem@davemloft.net> Sender: netdev-owner@vger.kernel.org List-ID: On Sun, Nov 08, 2009 at 01:05:33AM -0800, David Miller wrote: ... > > When using KGDBoE, gianfar driver spits 'Interrupt problem' messages, > > which appears to be a legitimate warning, i.e. we may end up calling > > netif_receive_skb() or vlan_hwaccel_receive_skb() with IRQs disabled. > > > > This patch reworks the RX path so that if netpoll is enabled (the > > only case when the driver don't know from what context the polling > > may be called), we check whether IRQs are disabled, and if so we > > fall back to safe variants of skb receiving functions. > > This is bogus, I'll tell you why. > > When you go into netif_receive_skb() we have a special check, > "if (netpoll_receive_skb(..." that takes care of all of the > details concerning doing a ->poll() from IRQ disabled context > via netpoll. > > So this code you're adding should not be necessary. > > Or, explain to me why no other driver needs special logic in their > ->poll() handler like this and does not run into any kinds of netpoll > problems :-) Hm, I was confused by the following note: /** * netif_receive_skb - process receive buffer from network * @skb: buffer to process ... * This function may only be called from softirq context and interrupts * should be enabled. Looking into the code though, I can indeed see that there are netpoll checks, and __netpoll_rx() is actually called with irqs disabled. So, in the end it appears that we should just remove the 'Interrupt problem' message. Thanks! -- Anton Vorontsov email: cbouatmailru@gmail.com irc://irc.freenode.net/bd2