Messages in this thread |  | | Date | Fri, 1 Nov 2013 10:29:42 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH 1/4] mm/rmap: per anon_vma lock |
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* Michel Lespinasse <walken@google.com> wrote:
> 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...
By the looks of it it seems to be an unintentional bug, not an intended feature.
Thanks,
Ingo
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