From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from buildserver.ru.mvista.com (unknown [213.79.90.228]) by ozlabs.org (Postfix) with ESMTP id 1F325B70B3 for ; Tue, 10 Nov 2009 00:32:35 +1100 (EST) Date: Mon, 9 Nov 2009 16:32:31 +0300 From: Anton Vorontsov To: David Miller Subject: Re: [PATCH RFC] gianfar: Make polling safe with IRQs disabled Message-ID: <20091109133231.GA26965@oksana.dev.rtsoft.ru> References: <20091104225711.GA30844@oksana.dev.rtsoft.ru> <20091108.010533.212571001.davem@davemloft.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 In-Reply-To: <20091108.010533.212571001.davem@davemloft.net> Cc: linuxppc-dev@ozlabs.org, netdev@vger.kernel.org, afleming@freescale.com, jason.wessel@windriver.com Reply-To: avorontsov@ru.mvista.com List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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