Messages in this thread | | | Date | Fri, 1 Nov 2013 02:22:25 -0700 | Subject | Re: [PATCH 1/4] mm/rmap: per anon_vma lock | From | Michel Lespinasse <> |
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On Fri, Nov 1, 2013 at 1:43 AM, Peter Zijlstra <peterz@infradead.org> wrote: > AFAICT this isn't correct at all. We used to protect the vma interval > tree with the root lock, now we don't. All we've got left is the > mmap_sem, but anon_vma chains can cross address-spaces and thus we're up > some creek without no paddle.
Yes, that was my first thought as well (though I wanted to double check at first).
I also want to point out that lately we've seen several changes sent out that relax locking with no accompanying explanation of why the relaxed locking would be safe. Please don't do that - having a lot of performance data is worthless if you can't explain why the new locking is safe. And I'm not asking to prove a negative ('lack of any possible races') there, but at least in this case one could dig out why the root anon vma locking was introduced and if they think that this reason doesn't apply anymore, explain why...
-- Michel "Walken" Lespinasse A program is never fully debugged until the last user dies.
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