linux-kernel - Re: [BUG] object: is not initialized, yet kobject

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Message-ID: <alpine.LNX.2.00.1008121510180.2702@pobox.suse.cz>
Date:	Thu, 12 Aug 2010 15:11:39 +0200 (CEST)
From:	Jiri Kosina <jkosina@...e.cz>
To:	Alan Ott <alan@...nal11.us>
Cc:	Markus Trippelsdorf <markus@...ppelsdorf.de>,
	Heinz Diehl <htd@...tha.org>, linux-kernel@...r.kernel.org,
	linux-usb@...r.kernel.org, linux-input@...r.kernel.org,
	Arnd Bergmann <arnd@...db.de>
Subject: Re: [BUG] object: is not initialized, yet kobject_put() is being  
 called

On Thu, 12 Aug 2010, Alan Ott wrote:

> > > > > commit bd25f4dd6972755579d0ea50d1a5ace2e9b00d1a
> > > > > Author: Arnd Bergmann<arnd@...db.de>
> > > > > Date:   Sun Jul 11 15:34:05 2010 +0200
> > > > > 
> > > > >      HID: hiddev: use usb_find_interface, get rid of BKL
> > > > > 
> > > > >      This removes the private hiddev_table in the usbhid
> > > > >      driver and changes it to use usb_find_interface
> > > > >      instead.
> > > > > 
> > > > >      The advantage is that we can avoid the race between
> > > > >      usb_register_dev and usb_open and no longer need the
> > > > >      big kernel lock.
> > > > > 
> > > > >      This doesn't introduce race condition -- the intf pointer could
> > > > > be
> > > > >      invalidated only in hiddev_disconnect() through
> > > > > usb_deregister_dev(),
> > > > >      but that will block on minor_rwsem and not actually remove the
> > > > > device
> > > > >      until usb_open().
> > > > > 
> > > > >      Signed-off-by: Arnd Bergmann<arnd@...db.de>
> > > > >      Cc: Jiri Kosina<jkosina@...e.cz>
> > > > >      Cc: "Greg Kroah-Hartman"<gregkh@...e.de>
> > > > >      Signed-off-by: Jiri Kosina<jkosina@...e.cz>
> > > > >          
> > > > Thanks, I had my suspicion about this commit (that's why I asked to you
> > > > verify with CONFIG_USB_HIDDEV turned off as well).
> > > > 
> > > > Adding Arnd to CC and will look into it myself as well soon.
> > > > 
> > > > Arnd, the complete thread can be found at
> > > > http://lkml.org/lkml/2010/8/10/280
> > > >        
> > > Could please those of you, who are able to reproduce the problem, verify
> > > whether the patch below (completely untested) makes everything behave
> > > again? Thanks.
> > >      
> > Yes, everything behaves again. Thanks Jiri.
> >    
> 
> Seconded. Works good. Thanks for your support Jiri.

Thanks for your testing. I still need to think a little bit more about 
whether this is indeed an appropriate fix or there might be still some 
problem.

Once I will be applying this, I will put

	Reported-and-tested-by: 

tag for both of you Alan and Markus, is that fine?

Thanks,

-- 
Jiri Kosina
SUSE Labs, Novell Inc.
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