From: Alexander Holler <holler@ahsoftware.de>
To: Greg KH <gregkh@linuxfoundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org, linux-fbdev@vger.kernel.org,
Florian Tobias Schandinat <FlorianSchandinat@gmx.de>,
Bernie Thompson <bernie@plugable.com>,
Steve Glendinning <steve.glendinning@shawell.net>,
stable@vger.kernel.org
Subject: Re: [PATCH 2/3 v2] fb: udlfb: fix hang at disconnect
Date: Tue, 05 Feb 2013 07:08:28 +0000 [thread overview]
Message-ID: <5110AFEC.8020406@ahsoftware.de> (raw)
In-Reply-To: <20130204192514.GA32318@kroah.com>
Am 04.02.2013 20:25, schrieb Greg KH:
> On Mon, Feb 04, 2013 at 08:17:04PM +0100, Alexander Holler wrote:
>> Am 04.02.2013 13:05, schrieb Alexander Holler:
>>> Am 04.02.2013 02:14, schrieb Greg KH:
>>>
>>>> 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
next prev parent reply other threads:[~2013-02-05 7:08 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-01-12 13:20 [PATCH] fb: udlfb: fix hang at disconnect Alexander Holler
2013-01-12 22:22 ` Bernie Thompson
2013-01-13 12:05 ` Alexander Holler
2013-01-13 12:24 ` Alexander Holler
2013-01-25 18:49 ` [PATCH 1/3] semaphore: introduce down_timeout_killable() Alexander Holler
2013-01-25 18:49 ` [PATCH 2/3 v2] fb: udlfb: fix hang at disconnect Alexander Holler
2013-01-29 0:22 ` Andrew Morton
2013-01-29 0:56 ` Alexander Holler
2013-01-29 10:35 ` Alexander Holler
2013-01-29 11:11 ` Alexander Holler
2013-01-29 15:51 ` Alexander Holler
2013-01-29 20:35 ` Alexander Holler
2013-01-29 20:56 ` Alexander Holler
2013-02-04 1:14 ` Greg KH
2013-02-04 12:05 ` Alexander Holler
2013-02-04 19:17 ` Alexander Holler
2013-02-04 19:25 ` Greg KH
2013-02-05 7:08 ` Alexander Holler [this message]
2013-02-05 17:22 ` Greg KH
2013-02-05 17:36 ` Alexander Holler
2013-02-08 4:07 ` Dave Airlie
2013-02-08 9:53 ` Alexander Holler
2013-01-25 18:49 ` [PATCH 3/3] fb: smscufx: " Alexander Holler
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