Re: [PATCH] slub: Fix sysfs circular locking dependency

[David Rientjes]

On Thu, 6 Jan 2011, Christoph Lameter wrote:

> slab_mem_going_online_callback() etc already take the slub_lock since they
> have to iterate over the list of slab caches in existence. We could take
> the hotplug lock there as well.
> 
> Kame-san: Can you enlighten us on hotplug locking? And also check this
> patch?
> 

Yeah, I was going to suggest doing the lock_memory_hotplug() before taking 
slub_lock in the callback, but I really think it should be done in 
online_pages().  Since the offline case is already handled, this would 
expand the semantics of lock_memory_hotplug() to serialize the access of 
data structures that can change in a memory hotplug notifier callback 
without locking at the lower level.
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