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

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Message-ID: <m1prajme2y.fsf@fess.ebiederm.org>
Date:	Tue, 25 Aug 2009 20:47:01 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Francois Romieu <romieu@...zoreil.com>
Cc:	David Dillow <dave@...dillows.org>,
	Michael Riepe <michael.riepe@...glemail.com>,
	Michael Buesch <mb@...sch.de>,
	Rui Santos <rsantos@...popie.com>,
	Michael B??ker <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

Francois Romieu <romieu@...zoreil.com> writes:

> Eric W. Biederman <ebiederm@...ssion.com> :
> [...]
>> I am a bit curious about TxDescUnavail.  Perhaps we had a temporary
>> memory shortage and that is what was screaming?  I don't think we do
>> anything at all with that state.
>
> You are not alone, the driver completely ignores this bit.
>
> As far as I remember, the TxDescUnavail event mostly pops up when the
> driver makes an excessive use of TxPoll requests.
>
>> Perhaps the flaw here is simply not masking TxDescUnavail while we are
>> in NAPI mode ?
>
> Yes, it is worth trying.

At first blush things seem better, but it isn't sufficient.
I still have a problem with RxFIFOOver set.
r8169 screaming irq status 00000040 mask 0000ffe2 event 0000803f napi 0000001d

The patch I ran is below.

Eric

---
 drivers/net/r8169.c |   12 ++++++++++++
 1 files changed, 12 insertions(+), 0 deletions(-)

diff --git a/drivers/net/r8169.c b/drivers/net/r8169.c
index 3b19e0c..e144bc1 100644
--- a/drivers/net/r8169.c
+++ b/drivers/net/r8169.c
@@ -3552,6 +3552,7 @@ 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.
@@ -3560,6 +3561,14 @@ 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.
 		 */
@@ -3609,6 +3618,9 @@ static irqreturn_t rtl8169_interrupt(int irq, void *dev_instance)
 		RTL_W16(IntrStatus,
 			(status & RxFIFOOver) ? (status | RxOverflow) : status);
 		status = RTL_R16(IntrStatus);
+		if (status == 0xffff)
+			break;
+		status &= tp->intr_mask;
 	}
 
 	return IRQ_RETVAL(handled);
-- 
1.6.2.5

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