From mboxrd@z Thu Jan  1 00:00:00 1970
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Subject: Re: [PATCH 1/3] Input: sysrq - drop tty argument from sysrq ops
 handlers
Date: Thu, 05 Aug 2010 12:03:05 +1000
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To: Jason Wessel <jason.wessel@windriver.com>
Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>, linux-input@vger.kernel.org, linux-kernel@vger.kernel.org, David Airlie <airlied@linux.ie>, David Miller <davem@davemloft.net>, Fenghua Yu <fenghua.yu@intel.com>, Greg Kroah-Hartman <gregkh@suse.de>, Martin Schwidefsky <schwidefsky@de.ibm.com>, Russell King <linux@arm.linux.org.uk>, Tony Luck <tony.luck@intel.com>

On Wed, 2010-08-04 at 07:03 -0500, Jason Wessel wrote:
> The usb serial has the same kind of problem with all sorts of locks.
> I
> had resorted to using a tasklet or workqueue to get the sysrq to
> execute
> just outside the usb serial driver context.  This work never made it
> upstream because it was part of another series, but the reference is:
> http://lkml.org/lkml/2010/3/9/17
> 
> For the standard serial you might be able to get away with dropping
> the
> lock for the sysrq.
> 
> Did you have a particular way to trigger the problem or was it just
> completely random, because I don't know that I have observed this
> behavior with the typical 8250 driver.

Yes, I do actually :-) A 64-way machine and a bunch of processes
flooding the console will do it just fine :-)

Cheers,
Ben.