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: Wed, 04 Aug 2010 18:33:50 +1000
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To: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: 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>, Jason Wessel <jason.wessel@windriver.com>, 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 00:59 -0700, Dmitry Torokhov wrote:
> Noone is using tty argument so let's get rid of it.

While talking about sysrq...

I noticed that serial drivers call sysrq with the uart lock held.

I've seen deadlocks caused by that, for example, when entering the
debugger, it waits forever for a CPU which is itself waiting on the UART
lock.

I have a patch to drop the lock in serial_core.h, I'll post that
tomorrow hopefully, just checking if there's any objection there ? The
serial drivers might need to be audited a bit to make sure they cope
with the lock being dropped and re-acquired around the sysrq call.

Cheers,
Ben.