Messages in this thread | | | Subject | Re: [mm][RFC][PATCH 0/11] mm accessor updates. | From | Peter Zijlstra <> | Date | Thu, 17 Dec 2009 00:01:55 +0100 |
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On Wed, 2009-12-16 at 10:27 -0600, Christoph Lameter wrote: > On Wed, 16 Dec 2009, Andi Kleen wrote: > > > > Do you have alternative recommendation rather than wrapping all accesses by > > > special functions ? > > > > Work out what changes need to be done for ranged mmap locks and do them all > > in one pass. > > Locking ranges is already possible through the split ptlock and > could be enhanced through placing locks in the vma structures. > > That does nothing solve the basic locking issues of mmap_sem. We need > Kame-sans abstraction layer. A vma based lock or a ptlock still needs to > ensure that the mm struct does not vanish while the lock is held.
It should, you shouldn't be able to remove a mm while there's still vma's around, and you shouldn't be able to remove a vma when there's still pagetables around. And if you rcu-free all of them you're stable enough for lots of speculative behaviour.
No need to retain mmap_sem for any of that.
As for per-vma locks, those are pretty much useless too, there's plenty applications doing lots of work on a few very large vmas.
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