Re: EMM: disable other notifiers before register and unregister

[Christoph Lameter]

On Thu, 3 Apr 2008, Andrea Arcangeli wrote:

> My attempt to fix this once and for all is to walk all vmas of the
> "mm" inside mmu_notifier_register and take all anon_vma locks and
> i_mmap_locks in virtual address order in a row. It's ok to take those
> inside the mmap_sem. Supposedly if anybody will ever take a double
> lock it'll do in order too. Then I can dump all the other locking and

What about concurrent mmu_notifier registrations from two mm_structs 
that have shared mappings? Isnt there a potential deadlock situation?

> faults). So it should be ok to take all those locks inside the
> mmap_sem and implement a lock_vm(mm) unlock_vm(mm). I'll think more
> about this hammer approach while I try to implement it...

Well good luck. Hopefully we will get to something that works.

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