From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: Re: [GIT]: Networking Date: Fri, 03 Jul 2009 00:32:54 +0200 Message-ID: <4A4D3596.8060209@gmail.com> References: <20090630.213927.180401151.davem@davemloft.net> <20090702075724.GA10608@elte.hu> <4A4C9125.8020705@gmail.com> <4A4CBE7D.2060603@gmail.com> <4A4CDCA4.3040505@nvidia.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: David Miller , "netdev@vger.kernel.org" , "linux-kernel@vger.kernel.org" To: Ayaz Abdulla Return-path: Received: from gw1.cosmosbay.com ([212.99.114.194]:39494 "EHLO gw1.cosmosbay.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755022AbZGBWdB (ORCPT ); Thu, 2 Jul 2009 18:33:01 -0400 In-Reply-To: <4A4CDCA4.3040505@nvidia.com> Sender: netdev-owner@vger.kernel.org List-ID: Ayaz Abdulla a =E9crit : >=20 >=20 > Eric Dumazet wrote: >> Eric Dumazet a =E9crit : >> >>> Ingo Molnar a =E9crit : >>> >>>>> The following changes since commit >>>>> 52989765629e7d182b4f146050ebba0abf2cb0b7: >>>>> Linus Torvalds (1): >>>>> Merge git://git.kernel.org/.../davem/net-2.6 >>>>> >>>>> are available in the git repository at: >>>>> >>>>> master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6.git ma= ster >>>> >>>> Hm, something in this lot quickly wrecked networking here - see th= e >>>> tx timeout dump below. It starts with: >>>> >>>> [ 351.004596] WARNING: at net/sched/sch_generic.c:246 >>>> dev_watchdog+0x10b/0x19c() >>>> [ 351.011815] Hardware name: System Product Name >>>> [ 351.016220] NETDEV WATCHDOG: eth0 (forcedeth): transmit queue 0 >>>> timed out >>>> >>>> Config attached. Unfortunately i've got no time to do bisection to= day. >>> >>> >>> >>> forcedeth might have a problem, in its netif_wake_queue() logic, bu= t >>> I could not see why a recent patch could make this problem visible = now. >>> >>> CPU0/1: AMD Athlon(tm) 64 X2 Dual Core Processor 3800+ stepping 02 >>> is not a new cpu either :) >>> >>> forcedeth uses an internal tx_stop without appropriate barrier. >>> >>> Could you try following patch ? >>> >>> (random guess as I dont have much time right now) >> >> >> Oh well this patch was soooo stupid, sorry Ingo. >> >> >> We might have a race in napi_schedule(), leaving interrupts disabled >> forever. >> I cannot test this patch, I dont have the hardware... >> >> Thanks >> >> diff --git a/drivers/net/forcedeth.c b/drivers/net/forcedeth.c >> index 1094d29..3b4e076 100644 >> --- a/drivers/net/forcedeth.c >> +++ b/drivers/net/forcedeth.c >> @@ -3514,11 +3514,13 @@ static irqreturn_t nv_nic_irq(int foo, void >> *data) >> nv_msi_workaround(np); >> =20 >> #ifdef CONFIG_FORCEDETH_NAPI >> - napi_schedule(&np->napi); >> - >> - /* Disable furthur irq's >> - (msix not enabled with napi) */ >> - writel(0, base + NvRegIrqMask); >> + if (napi_schedule_prep(&np->napi)) { >> + /* >> + * Disable further irq's (msix not enabled with napi) >> + */ >> + writel(0, base + NvRegIrqMask); >> + __napi_schedule(&np->napi); >> + } >=20 > Yes, good catch. There is a race condition here with napi poll. >=20 > I would prefer to do the following to keep the code simple and clean. >=20 > writel(0, base + NvRegIrqMask); > napi_schedule(&np->napi); CC trimmed down to network devs only :) It would be racy too ... check drivers/net/amd8111e.c, drivers/net/natsemi.c ... If this cpu inconditionaly calls writel(0, base + NvRegIrqMask);=20 while another cpu just called writel(np->irqmask, base + NvRegIrqMask), we end with disabled interrupts ?