[Devel] [PATCH RFC] slub: do not drop slab_mutex for sysfs_slab_{add, remove}

[Christoph Lameter]

On Thu, 6 Feb 2014, Vladimir Davydov wrote:

> When creating/destroying a kmem cache, we do a lot of work holding the
> slab_mutex, but we drop it for sysfs_slab_{add,remove} for some reason.
> Since __kmem_cache_create and __kmem_cache_shutdown are extremely rare,
> I propose to simplify locking by calling sysfs_slab_{add,remove} w/o
> dropping the slab_mutex.

The problem is that sysfs does nasty things like spawning a process in
user space that may lead to something wanting to create slabs too. The
module may then hang waiting on the lock ...

I would be very thankful, if you can get that actually working reliably
without deadlock issues.