On May 7, 2009, at 5:58 PM, Roland Dreier (rdreier) wrote:
> Specifically: the actual dereg of 0x1000-0x3fff is blocked on also
> releasing 0x2000-0x2fff.
If everyone is doing this, how do you handle the case that Jason
pointed
out, namely:
* you register 0x1000 ... 0x3fff
* you want to register 0x2000 ... 0x2fff and have a cache hit
* you finish up with 0x1000 ... 0x3fff
* app does something (which is valid since you finished up with the
bigger range) that invalidates mapping 0x3000 ... 0x3fff (eg free()
that leads to munmap() or whatever), and your hooks tell you so.
* app reallocates a mapping in 0x3000 ... 0x3fff
* you want to re-register 0x1000 ... 0x3fff -- but it has to be
marked
both invalid and in-use in the cache at this point !?
Sorry; this mail slipped by me and I just saw it now.
If this can actually happen -- that the mapping of 0x1000 ... 0x3fff
can change even though it is still registered, then we're screwed --
we have no way of knowing that this is now invalid (Open MPI, at least
-- can't speak for others).
Is there a way to detect condition this in userspace?
--
Jeff Squyres
Cisco Systems
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