linux-kernel - Re: [PATCH 2/3 v2] fb: udlfb: fix hang at disconnect

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Date:	Tue, 29 Jan 2013 21:56:47 +0100
From:	Alexander Holler <holler@...oftware.de>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	linux-kernel@...r.kernel.org, linux-fbdev@...r.kernel.org,
	Florian Tobias Schandinat <FlorianSchandinat@....de>,
	Bernie Thompson <bernie@...gable.com>,
	Steve Glendinning <steve.glendinning@...well.net>,
	stable@...r.kernel.org
Subject: Re: [PATCH 2/3 v2] fb: udlfb: fix hang at disconnect

Am 29.01.2013 21:35, schrieb Alexander Holler:
>
> So, if the above down_timeout_killable() is only down_interruptible(),
> as in kernel 3.7.5, the  box would not shutdown afterwards, because on
> shutdown no signal would be send to that kernel-thread which called
> dlfb_free_urb_list().
>
> A last note: dlfb_usb_disconnect() (thus dlfb_free_urb_list()) isn't
> called on shutdown if the device would still be connected. So the
> problem only might happen, if the screen will be disconnected before
> shutdown (and an urb gets missed). So the subject of my patch is
> correct. ;)
>
> </monologue>

Hmm, wrong, sorry, I still have something to add: As no signal arrives 
at all, v1 of that patch is enough and the implementation of 
down_timeout_killable() isn't necessary at all.

If there is a chance that the patch would be Acked-by by someone, I 
would made a v3, replacing

+		ret = down_timeout(&dev->urbs.limit_sem, GET_URB_TIMEOUT);

in v1 with

+		ret = down_timeout(&dev->urbs.limit_sem, FREE_URB_TIMEOUT);

as this seems to be what it should be.

Regards,

Alexander
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