linux-kernel - Re: [PATCH] i2c:at91: Fix a race condition during signal handling in at91_do_twi

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Date:	Tue, 2 Sep 2014 12:56:23 +0200
From:	Wolfram Sang <wsa@...-dreams.de>
To:	Simon Lindgren <simon@...ary.com>
Cc:	ludovic.desroches@...el.com, linux-i2c@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] i2c:at91: Fix a race condition during signal handling in
 at91_do_twi_xfer.

On Tue, Aug 26, 2014 at 09:13:24PM +0200, Simon Lindgren wrote:
> There is a race condition in at91_do_twi_xfer when signals arrive.
> If a signal is recieved while waiting for a transfer to complete
> wait_for_completion_interruptible_timeout() will return -ERESTARTSYS.
> This is not handled correctly resulting in interrupts still being
> enabled and a transfer being in flight when we return.
> 
> Symptoms include a range of oopses and bus lockups. Oopses can happen
> when the transfer completes because the interrupt handler will corrupt
> the stack. If a new transfer is started before the interrupt fires
> the controller will start a new transfer in the middle of the old one,
> resulting in confused slaves and a locked bus.
> 
> To avoid this, use wait_for_completion_io_timeout instead so that we
> don't have to deal with gracefully shutting down the transfer and
> disabling the interrupts.
> 
> Signed-off-by: Simon Lindgren <simon@...ary.com>

Applied to for-current, thanks!


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