netdev - Re: [PATCH 2.6.30-rc4] r8169: avoid losing MSI interrupts

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Message-Id: <1250897657.23419.5.camel@obelisk.thedillows.org>
Date:	Fri, 21 Aug 2009 19:34:17 -0400
From:	David Dillow <dave@...dillows.org>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Michael Riepe <michael.riepe@...glemail.com>,
	Michael Buesch <mb@...sch.de>,
	Francois Romieu <romieu@...zoreil.com>,
	Rui Santos <rsantos@...popie.com>,
	Michael Büker <m.bueker@...lin.de>,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH 2.6.30-rc4] r8169: avoid losing MSI interrupts

On Fri, 2009-08-21 at 18:59 -0400, David Dillow wrote:
> On Fri, 2009-08-21 at 13:57 -0700, Eric W. Biederman wrote:
> > David Dillow <dave@...dillows.org> writes:
> > I have what at first glance looks like a problem caused by this
> > patch.  For the last month since upgrading one of my machines from
> > 2.6.28 to 2.6.30 it has been becomming inaccessible from the
> > network and I have a few:
> > 
> > NETDEV WATCHDOG: eth0 (r8169): transmit timed out
> > 
> > in my logs and a lot soft lockups that always have rtl8169_interrupt
> > as the thing that is running.   I suspect your patch has introduced
> > a near infinite loop in the interrupt handler and is causing these
> > soft lockups.
> > 
> > Any ideas?
> 
> I would be surprised, but I suppose it is not out of the realm of
> possibility. Can you send me a full dmesg, please?

Re-looking at the code, I'd guess that some IRQ status line is getting
stuck high, but I don't see why -- we should acknowledge all outstanding
interrupts each time through the loop, whether we care about them or
not.

Could reproduce a problem with the following patch applied, and send the
full dmesg, please?

diff --git a/drivers/net/r8169.c b/drivers/net/r8169.c
index b82780d..46cb05a 100644
--- a/drivers/net/r8169.c
+++ b/drivers/net/r8169.c
@@ -3556,6 +3556,7 @@ static irqreturn_t rtl8169_interrupt(int irq, void *dev_instance)
 	void __iomem *ioaddr = tp->mmio_addr;
 	int handled = 0;
 	int status;
+	int count = 0;
 
 	/* loop handling interrupts until we have no new ones or
 	 * we hit a invalid/hotplug case.
@@ -3564,6 +3565,15 @@ static irqreturn_t rtl8169_interrupt(int irq, void *dev_instance)
 	while (status && status != 0xffff) {
 		handled = 1;
 
+		if (count++ > 100) {
+			printk_once("r8169 screaming irq status %08x "
+				"mask %08x event %08x napi %08x\n",
+				status, tp->intr_mask, tp->intr_event,
+				tp->napi_event);
+			break;
+		}
+
+
 		/* Handle all of the error cases first. These will reset
 		 * the chip, so just exit the loop.
 		 */


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