Messages in this thread |  | | Date | Fri, 21 Feb 2014 13:24:33 -0800 | Subject | Re: [PATCH] mm: per-thread vma caching | From | Linus Torvalds <> |
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On Fri, Feb 21, 2014 at 12:57 PM, Davidlohr Bueso <davidlohr@hp.com> wrote: > > Btw, one concern I had is regarding seqnum overflows... if such > scenarios should happen we'd end up potentially returning bogus vmas and > getting bus errors and other sorts of issues. So we'd have to flush the > caches, but, do we care? I guess on 32bit systems it could be a bit more > possible to trigger given enough forking.
I guess we should do something like
if (unlikely(!++seqnum)) flush_vma_cache()
just to not have to worry about it.
And we can either use a "#ifndef CONFIG_64BIT" to disable it for the 64-bit case (because no, we really don't need to worry about overflow in 64 bits ;), or just decide that a 32-bit sequence number actually packs better in the structures, and make it be an "u32" even on 64-bit architectures?
It looks like a 32-bit sequence number might pack nicely next to the
unsigned brk_randomized:1;
but I didn't actually go and look at the context there to see what else is there..
Linus
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