Date: Wed, 10 Nov 2004 03:25:35 +0100
From: Kay Sievers <kay.sievers@vrfy.org>
To: Greg KH <greg@kroah.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: /sys/devices/system/timer registered twice
Message-ID: <20041110022535.GA10011@vrfy.org>
References: <20041109193043.GA8767@vrfy.org> <20041109193947.GA5758@kroah.com>
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On Tue, Nov 09, 2004 at 11:39:47AM -0800, Greg KH wrote:
> On Tue, Nov 09, 2004 at 08:30:43PM +0100, Kay Sievers wrote:
> > Hi,
> > I got this on a Centrino box with the latest bk:
> > 
> >   [kay@pim linux.kay]$ ls -l /sys/devices/system/
> >   total 0
> >   drwxr-xr-x  7 root root 0 Nov  8 15:12 .
> >   drwxr-xr-x  5 root root 0 Nov  8 15:12 ..
> >   drwxr-xr-x  3 root root 0 Nov  8 15:12 cpu
> >   drwxr-xr-x  3 root root 0 Nov  8 15:12 i8259
> >   drwxr-xr-x  2 root root 0 Nov  8 15:12 ioapic
> >   drwxr-xr-x  3 root root 0 Nov  8 15:12 irqrouter
> >   ?---------  ? ?    ?    ?            ? timer
> > 
> > 
> > It is caused by registering two devices with the name "timer" from:
> > 
> >   arch/i386/kernel/time.c
> >   arch/i386/kernel/timers/timer_pit.c
> > 
> > If I change one of the names, I get two correct looking sysfs entries.
> > 
> > Greg, shouldn't the driver core prevent the corruption of the first
> > device if another one tries to register with the same name?
> 
> Yes, we should handle this.  Can you try the patch below?  I just sent
> it to Linus, as it fixes a bug that was recently introduced.
> 
> The second registration should fail, and this patch will make it fail,
> and recover properly.

Yes, the registration fails. But it seems that the second call to
create_dir(kobj) with a kobject with the same name and parent corrupts
the dentry from the first call.

To test it, I just called create_dir(kobj) a second time for my video
driver and the sysfs entry of the successful registered kobject was
corrupted:

  [kay@pim ~]$ ls -la /sys/class/video4linux/
  total 0
  drwxr-xr-x   3 root root 0 Nov 10 02:53 .
  drwxr-xr-x  18 root root 0 Nov 10 02:53 ..
  ?---------   ? ?    ?    ?            ? video0

Thanks,
Kay
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