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From: Greg KH <gregkh@linuxfoundation.org>
To: Alexander Holler <holler@ahsoftware.de>
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, 5 Feb 2013 09:22:45 -0800	[thread overview]
Message-ID: <20130205172245.GA1426@kroah.com> (raw)
In-Reply-To: <5110AFEC.8020406@ahsoftware.de>

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

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

WARNING: multiple messages have this Message-ID (diff)
From: Greg KH <gregkh@linuxfoundation.org>
To: Alexander Holler <holler@ahsoftware.de>
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 17:22:45 +0000	[thread overview]
Message-ID: <20130205172245.GA1426@kroah.com> (raw)
In-Reply-To: <5110AFEC.8020406@ahsoftware.de>

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

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

  reply	other threads:[~2013-02-05 17:20 UTC|newest]

Thread overview: 46+ 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 13:20 ` Alexander Holler
2013-01-12 22:22 ` Bernie Thompson
2013-01-12 22:22   ` Bernie Thompson
2013-01-13 12:05   ` Alexander Holler
2013-01-13 12:05     ` Alexander Holler
2013-01-13 12:24     ` 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       ` Alexander Holler
2013-01-25 18:49       ` [PATCH 2/3 v2] fb: udlfb: fix hang at disconnect Alexander Holler
2013-01-25 18:49         ` Alexander Holler
2013-01-29  0:22         ` Andrew Morton
2013-01-29  0:22           ` Andrew Morton
2013-01-29  0:56           ` Alexander Holler
2013-01-29  0:56             ` Alexander Holler
2013-01-29 10:35             ` Alexander Holler
2013-01-29 10:35               ` Alexander Holler
2013-01-29 11:11               ` Alexander Holler
2013-01-29 11:11                 ` Alexander Holler
2013-01-29 15:51                 ` Alexander Holler
2013-01-29 15:51                   ` Alexander Holler
2013-01-29 20:35                   ` Alexander Holler
2013-01-29 20:35                     ` Alexander Holler
2013-01-29 20:56                     ` Alexander Holler
2013-01-29 20:56                       ` Alexander Holler
2013-02-04  1:14                     ` Greg KH
2013-02-04  1:14                       ` Greg KH
2013-02-04 12:05                       ` Alexander Holler
2013-02-04 12:05                         ` Alexander Holler
2013-02-04 19:17                         ` Alexander Holler
2013-02-04 19:17                           ` Alexander Holler
2013-02-04 19:25                           ` Greg KH
2013-02-04 19:25                             ` Greg KH
2013-02-05  7:08                             ` Alexander Holler
2013-02-05  7:08                               ` Alexander Holler
2013-02-05 17:22                               ` Greg KH [this message]
2013-02-05 17:22                                 ` Greg KH
2013-02-05 17:36                                 ` Alexander Holler
2013-02-05 17:36                                   ` Alexander Holler
2013-02-08  4:07                                   ` Dave Airlie
2013-02-08  4:07                                     ` Dave Airlie
2013-02-08  9:53                                     ` Alexander Holler
2013-02-08  9:53                                       ` Alexander Holler
2013-01-25 18:49       ` [PATCH 3/3] fb: smscufx: " Alexander Holler
2013-01-25 18:49         ` Alexander Holler

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