linux-kernel - Re: 2.6.19-rc1-mm1 - locks when using "dd bs=1M" from card reader

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Date:	Thu, 12 Oct 2006 11:29:38 -0700
From:	Andrew Morton <akpm@...l.org>
To:	Helge Hafting <helge.hafting@...el.hist.no>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: 2.6.19-rc1-mm1 - locks when using "dd bs=1M" from card reader

On Thu, 12 Oct 2006 14:18:04 +0200
Helge Hafting <helge.hafting@...el.hist.no> wrote:

> I found an easy way to hang the kernel when copying a SD-card:
> 
> dd if=/dev/sdc of=file bs=1048576
> 
> I.e. copy the entire 256MB card in 1MB chunks.  I got about
> 160MB before the kernel hung.  Not even sysrq+B worked, I needed
> the reset button.  The pc has a total of 512MB memory if that matters.
> 
> Using bs=4096 instead let me copy the entire card with no problems,
> but that seems to progress slower.
> 
> The above 'dd' command hangs my office pc every time. So I can repeat
> it for debugging purposes. 
> 

What device driver is providing /dev/sdc?

Did any previous kernels work correctly?  If so, which?
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