Re: /sys/devices/system/timer registered twice

Greg KH
2004-11-12T21:31:51Z

On Wed, Nov 10, 2004 at 04:36:29PM -0600, Maneesh Soni wrote:
> On Wed, Nov 10, 2004 at 03:25:35AM +0100, Kay Sievers wrote:
> > 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 for reporting this bug. I think the problem here is doing d_drop()
> for the existing directory dentry in create_dir() for error case. It should
> not be done for EEXIST. Could you please try the same test with the following
> patch applied.
>
> Thanks
> Maneesh
>
> o Do not release existing directory if the new directory happens to be a
> duplicate directory. Thanks to Kay Sievers for the testcase.
>
> Signed-off-by: <maneesh@in.ibm.com>

Applied, thanks.

greg k-h