From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ayaz Abdulla Subject: Re: [GIT]: Networking Date: Thu, 02 Jul 2009 13:29:35 -0400 Message-ID: <4A4CEE7F.9060705@nvidia.com> References: <20090630.213927.180401151.davem@davemloft.net> <20090702075724.GA10608@elte.hu> <4A4C9125.8020705@gmail.com> <4A4CBE7D.2060603@gmail.com> <4A4CDCA4.3040505@nvidia.com> <4A4D3596.8060209@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: David Miller , "netdev@vger.kernel.org" To: Eric Dumazet Return-path: Received: from hqemgate03.nvidia.com ([216.228.112.145]:2507 "EHLO hqemgate03.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751139AbZGBW75 (ORCPT ); Thu, 2 Jul 2009 18:59:57 -0400 In-Reply-To: <4A4D3596.8060209@gmail.com> Sender: netdev-owner@vger.kernel.org List-ID: Eric Dumazet wrote: > Ayaz Abdulla a =E9crit : >=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); >>>+ } >> >>Yes, good catch. There is a race condition here with napi poll. >> >>I would prefer to do the following to keep the code simple and clean. >> >>writel(0, base + NvRegIrqMask); >>napi_schedule(&np->napi); >=20 >=20 >=20 > CC trimmed down to network devs only :) >=20 > It would be racy too ... >=20 > check drivers/net/amd8111e.c, drivers/net/natsemi.c ... >=20 > 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 ? Yes, but the next instruction is to call napi_schedule() which will=20 re-enable interrupts in napi function. >=20