Re: [mm][RFC][PATCH 0/11] mm accessor updates.

[Christoph Lameter]

On Thu, 17 Dec 2009, Andi Kleen wrote:

> > There are a few interesting cases like stack extention and hugetlbfs,
> > but I think we could start by falling back to mmap_sem locked behaviour
> > if the speculative thing fails.
>
> You mean fall back to mmap_sem if anything sleeps? Maybe. Would need
> to check how many such points are really there.

You always need some reference on the mm_struct (mm_read_lock) if you are
going to sleep to ensure that mm_struct still exists after waking up (page
fault, page allocation). RCU and other spin locks are not helping there.

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