Re: md deadlock (was Re: 2.6.18-mm2)

Peter Zijlstra
2006-09-29T14:04:36Z

On Fri, 2006-09-29 at 22:52 +1000, Neil Brown wrote:
> On Friday September 29, a.p.zijlstra@chello.nl wrote:
> > On Thu, 2006-09-28 at 13:54 +0200, Michal Piotrowski wrote:
> >
> > Looks like a real deadlock here. It seems to me #2 is the easiest to
> > break.
>
> I guess it could deadlock if you tried to add /dev/md0 as a component
> of /dev/md0. I should probably check for that somewhere.
> In other cases the array->member ordering ensures there is no
> deadlock.
>

1 2

open(/dev/md0)

open(/dev/md0)
- do_open() -> bdev->bd_mutex
ioctl(/dev/md0, hotadd)
- md_ioctl() -> mddev->reconfig_mutex
-- hot_add_disk()
--- bind_rdev_to_array()
---- bd_claim_by_disk()
----- bd_claim_by_kobject()
-- md_open()
--- mddev_lock()
---- mutex_lock(mddev->reconfig_mutex)
------ mutex_lock(bdev->bd_mutex)

looks like an AB-BA deadlock to me