Re: [PATCH] mm: prevent mmap_cache race in find_vma()

[Linus Torvalds]

On Thu, Apr 4, 2013 at 11:35 AM, Hugh Dickins <hughd@xxxxxxxxxx> wrote:
>
> find_vma() can be called by multiple threads with read lock
> held on mm->mmap_sem and any of them can update mm->mmap_cache.
> Prevent compiler from re-fetching mm->mmap_cache, because other
> readers could update it in the meantime:

Ack. I do wonder if we should mark the unlocked update too some way
(also in find_vma()), although it's probably not a problem in practice
since there's no way the compiler can reasonably really do anything
odd with it. We *could* make that an ACCESS_ONCE() write too just to
highlight the fact that it's an unlocked write to this optimistic data
structure.

Anyway, applied.

                  Linus
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