linux-kernel - Re: [PATCH] ircomm: release tty before sleeping potentially indefintely

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Date:	Sun, 03 Mar 2013 18:17:38 -0500
From:	Sasha Levin <sasha.levin@...cle.com>
To:	David Miller <davem@...emloft.net>
CC:	samuel@...tiz.org, gregkh@...uxfoundation.org, jslaby@...e.cz,
	peter@...leysoftware.com, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ircomm: release tty before sleeping potentially indefintely

On 03/03/2013 05:47 PM, David Miller wrote:
> From: Sasha Levin <sasha.levin@...cle.com>
> Date: Sun,  3 Mar 2013 17:35:53 -0500
> 
>> ircomm_tty_block_til_ready would hold tty lock while blocking. Since the sleep
>> might take a long time we can prevent other processes from accessing the tty,
>> causing hung tasks and a dead tty.
>>
>> Diagnosed-by: Peter Hurley <peter@...leysoftware.com>
>> Signed-off-by: Sasha Levin <sasha.levin@...cle.com>
> 
> But then you invalidate all of the tty state tests made under
> the lock at the beginning of this function, before enterring
> the loop.  If you drop the lock, those pieces of state could
> change.
> 
> I'm not applying this.

I'm unsure. A similar patch was applied back in 2010 that does the same thing
to a bunch of drivers, including the core tty code (e142a31da "tty: release
BTM while sleeping in block_til_ready").

This IR code looks very much like tty_port_block_til_ready() where it was
okay to do that change, so I should be the same with ircomm_tty_block_til_ready.


Thanks,
Sasha


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