From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [PATCH 5/5] net: sh_eth: use NAPI Date: Fri, 16 Mar 2012 02:15:38 -0700 (PDT) Message-ID: <20120316.021538.2022095011493944779.davem@davemloft.net> References: <4F62FDDA.9070708@renesas.com> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, linux-sh@vger.kernel.org To: yoshihiro.shimoda.uh@renesas.com Return-path: In-Reply-To: <4F62FDDA.9070708@renesas.com> Sender: linux-sh-owner@vger.kernel.org List-Id: netdev.vger.kernel.org From: "Shimoda, Yoshihiro" Date: Fri, 16 Mar 2012 17:46:18 +0900 sh_eth_interrupt takes mdp->lock, and: > +static int sh_eth_poll(struct napi_struct *napi, int budget) > +{ > + struct sh_eth_private *mdp = container_of(napi, struct sh_eth_private, > + napi); > + struct net_device *ndev = mdp->ndev; > + struct sh_eth_cpu_data *cd = mdp->cd; > + int work_done = 0, txfree_num; > + u32 intr_status = sh_eth_read(ndev, EESR); > + > + spin_lock(&mdp->lock); sh_eth_poll() runs from software interrupt context, therefore this can deadlock. Even though you turned off interrupts in sh_eth_interrupt to enable NAPI mode, this can still happen, interrupts can be stuck in the interrupt controller, another device can be on the same interrupt line, etc. Therefore you must handle this properly. I would suggest _NOT_ fixing this by taking the lock with interrupts disabled in sh_eth_poll(), that defeats the whole prupose of converting to NAPI and this would also require you to change back the dev_kfree_skb() to dev_kfree_skb_irq(). Instead, do what other drivers do, make your interrupt handler run completely lockless and have a sophisticated quiescence sequence when you want to sync interrupts off and make sure no async contexts are still running in the interrupt handler. See tg3.c for one example of this. I'm toss this entire patch series, it needs a lot more work.