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

On Tue, Feb 05, 2013 at 08:08:28AM +0100, Alexander Holler wrote:

Am 04.02.2013 20:25, schrieb Greg KH:

quoted

On Mon, Feb 04, 2013 at 08:17:04PM +0100, Alexander Holler wrote:

quoted

Am 04.02.2013 13:05, schrieb Alexander Holler:

quoted

Am 04.02.2013 02:14, schrieb Greg KH:

quoted

So you are right in that your driver will wait for forever for a
disconnect() to happen, as it will never be called.  I don't understand
the problem that this is causing when it happens.  What's wrong with
udlfb that having the cpu suddently reset as the powerdown happened
without it knowing about it?

There is nothing wrong with that. I've just explained why a problem
doesn't occur on shutdown but on disconnect (of the device).

Maybe my explanation before was just to long and I try to explain it
a bit shorter:

If a device gets disconnected, the disconnect in udlfb might wait
forever in down_interruptible() (because it waits for an urb it
never receives). This even prevents a shutdown afterwards, because
that down_interruptible() never receives a signal (at shutdown,
because kernel threads don't get such).

Where was that urb when the disconnect happened?  The USB core should
call your urb callback for any outstanding urbs at that point in time,
with the proper error flag being set, are you handling that properly?

I don't know where that urb is as I don't handle it.

What do you mean by that?  The urb is being sent back to your driver,
right?  If not, that's a bug, but please be sure that your urb callback
isn't really being called.

thanks,

greg k-h