Re: zap_page_range(): TLB flush race

From: Jamie Lokier (lk@tantalophile.demon.co.uk)
Date: Wed Apr 12 2000 - 05:02:44 EST


Manfred Spraul wrote:
> Can we ignore the munmap+access case?
> I'd say that if 2 threads race with munmap+access, then the behaviour is
> undefined.
> Tlb flushes are expensive, I'd like to avoid the second tlb flush as in
> Kanoj's patch.

No, you can't ignore it. A variation called mprotect+access is used by
garbage collection systems that expect to receive SEGVs when access is
to a protected region.

At very least, you'd have to document the race very clearly, and provide
a workaround.

-- Jamie

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