netdev - Re: [Bugme-new] [Bug 38102] New: BUG kmalloc-2048: Poison overwritten

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Date:	Tue, 05 Jul 2011 18:57:30 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Neil Horman <nhorman@...driver.com>
Cc:	Alexey Zaytsev <alexey.zaytsev@...il.com>,
	Michael Büsch <m@...s.ch>,
	Andrew Morton <akpm@...ux-foundation.org>,
	netdev@...r.kernel.org, Gary Zambrano <zambrano@...adcom.com>,
	bugme-daemon@...zilla.kernel.org,
	"David S. Miller" <davem@...emloft.net>,
	Pekka Pietikainen <pp@...oulu.fi>,
	Florian Schirmer <jolt@...box.org>,
	Felix Fietkau <nbd@...nwrt.org>, Michael Buesch <mb@...sch.de>
Subject: Re: [Bugme-new] [Bug 38102] New: BUG kmalloc-2048: Poison
 overwritten

Le mardi 05 juillet 2011 à 18:47 +0200, Eric Dumazet a écrit :
> Le mardi 05 juillet 2011 à 12:42 -0400, Neil Horman a écrit :
> > On Tue, Jul 05, 2011 at 06:12:32PM +0200, Eric Dumazet wrote:
> 
> > > So all descriptors before prod are guaranteed to be ready for host
> > > consume... Fact that a dma access is running on 'next descriptor' should
> > > be irrelevant.
> > > 
> > But we handle more than one descriptor per b44_rx call - theres a while loop in
> > there where we do advance to the next descriptor.
> 
> Yes, but we advance up to 'prod', which is the very last safe
> descriptor.
> 
> If hardware advertises descriptor X being ready to be handled by host,
> while DMA on this X descriptor is not yet finished, this would be a
> really useless hardware ;)
> 
> 


BTW the code around line 782 seems really suspect.

We should log an error once, just in case...

diff --git a/drivers/net/b44.c b/drivers/net/b44.c
index 98c977e..bc7ce27 100644
--- a/drivers/net/b44.c
+++ b/drivers/net/b44.c
@@ -781,6 +781,7 @@ static int b44_rx(struct b44 *bp, int budget)
 		if (len == 0) {
 			int i = 0;
 
+			pr_err_once("b44: zero len !\n");
 			do {
 				udelay(2);
 				barrier();


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