Thread (23 messages) 23 messages, 5 authors, 2013-02-08

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

From: Alexander Holler <hidden>
Date: 2013-02-05 07:08:50
Also in: lkml, stable

Am 04.02.2013 20:25, schrieb Greg KH:
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. I just know that
_interruptible doesn't make any sense and _timeout is necessary here.
But as nobody else seems to have a problem, nobody else see seems to see
the problem there and I seem to be unable to explain it, just ignore
that patch.

Regards,

Alexander
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