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

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Message-ID: <20110705182703.0bb9eb33@maggie>
Date:	Tue, 5 Jul 2011 18:27:03 +0200
From:	Michael Büsch <m@...s.ch>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Neil Horman <nhorman@...driver.com>,
	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

On Tue, 05 Jul 2011 18:12:32 +0200
Eric Dumazet <eric.dumazet@...il.com> wrote:
> Hmm... We are in a NAPI handler... There wont be a new interrupt.
> 
> Plus, we do at start of b44_rx() :
> 
> prod  = br32(bp, B44_DMARX_STAT) & DMARX_STAT_CDMASK;
> 
> 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.
> 
> IMHO Peeking B44_DMARX_STAT for each packet would be a waste of time.

Yeah I think so, too. We don't need to wait for the _whole_ DMA engine
to go idle, before we can access a buffer in the ring. We just need to make sure
that the device is finished with that buffer. And we do this by reading the current
descriptor pointer.
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