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

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Date:	Mon, 04 Jul 2011 17:12:03 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Michael Büsch <m@...s.ch>
Cc:	Alexey Zaytsev <alexey.zaytsev@...il.com>,
	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 lundi 04 juillet 2011 à 16:43 +0200, Michael Büsch a écrit :
> On Mon, 4 Jul 2011 16:27:26 +0200
> Michael Büsch <m@...s.ch> wrote:
> > We do this in b43, which has exactly the same DMA engine.
> 
> (Ok, it turns out we don't do this in b43 (We only do it on the TX side).
>  But that's a bug. We should do a wmb() on the RX side before advancing the
>  descriptor ring pointer.)

I am wondering what happens if RX ring is set to 64, and we receive
exactly 64 buffers in one round, B44_DMARX_PTR wont change at all ?

Alexey, could you try this patch please ?

diff --git a/drivers/net/b44.c b/drivers/net/b44.c
index a69331e..51072a3 100644
--- a/drivers/net/b44.c
+++ b/drivers/net/b44.c
@@ -829,6 +829,7 @@ static int b44_rx(struct b44 *bp, int budget)
 	}
 
 	bp->rx_cons = cons;
+	wmb();
 	bw32(bp, B44_DMARX_PTR, cons * sizeof(struct dma_desc));
 
 	return received;


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