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

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Date:	Fri, 20 Oct 2006 13:44:09 +0200
From:	Helge Hafting <helge.hafting@...el.hist.no>
To:	Alan Stern <stern@...land.harvard.edu>
CC:	Christopher Monty Montgomery <xiphmont@...il.com>,
	Paolo Ornati <ornati@...twebnet.it>,
	Kernel development list <linux-kernel@...r.kernel.org>,
	USB development list <linux-usb-devel@...ts.sourceforge.net>
Subject: Re: [linux-usb-devel] 2.6.19-rc1-mm1 - locks when using "dd bs=1M"
 from card reader

Alan Stern wrote:
[...]
> After looking at the debugging output, no.  That "invalid opcode" is a red 
> herring.  What you encountered this time was a BUG() in the source code of 
> start_unlink_async() in drivers/usb/host/ehci-q.c:
>
> #ifdef DEBUG
> 	assert_spin_locked(&ehci->lock);
> 	if (ehci->reclaim
> 			|| (qh->qh_state != QH_STATE_LINKED
> 				&& qh->qh_state != QH_STATE_UNLINK_WAIT)
> 			)
> 		BUG ();
> #endif
>
> You could try putting a printk() just before the BUG() to display the 
> values of ehci->reclaim and qh->qh_state.  Maybe also change the BUG() to 
>   
ehci->reclaim=0
qh->qh_state=5
> WARN(), which might help prevent your system from crashing so badly.
>   
WARN didn't help much. I then got the warning twice, followed by
another BUG:
process klogd
ehci_irq
usb_hcd_irq
handle_IRQ_event
handle_fasteio_irq
do_IRQ

So I set it back to BUG. Crashing hard isn't so bad when I
know what is coming - I simply remount everything synchronously
before trying.

I hope these printk's help. I can add more of them too, if needed.
Big transfers seems to bring out the worst - I always get the
crash on the first megabyte now. 

During boot I get lots of those "Hardware error, end-of-data detected"
messages, but I've never seen it crash during bootup.

Helge Hafting
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