Messages in this thread | | | From | Nick Piggin <> | Subject | Re: GRU driver feedback | Date | Thu, 31 Jul 2008 17:14:04 +1000 |
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On Wednesday 30 July 2008 15:50, Nick Piggin wrote: > On Wednesday 30 July 2008 04:53, Robin Holt wrote:
> > In the case where unmap_region is clearing page tables, the caller to > > unmap_region is expected to be holding the mmap_sem writably. Jacks > > fault handler will immediately return when it fails on the > > down_read_trylock(). > > No, you are right of course. I had in my mind the problems faced by > lockless get_user_pages, in which case I was worried about the page table > existence, but missed the fact that you're holding mmap_sem to provide > existence (which it would, as you note, although one day we may want to > reclaim page tables or something that doesn't take mmap_sem, so a big > comment would be nice here).
The other thing is... then GRU should get rid of the local_irq_disable in the atomic pte lookup. By definition it is worthless if we can be operating on an mm that is not running on current (and if I understand correctly, sn2 can avoid sending tlb flush IPIs completely sometimes?)
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