On Wed, Jun 27, 2012 at 2:15 PM, Peter Zijlstra [off-list ref] wrote:

This originated from s390 which does something similar and would allow
s390 to use the generic TLB flushing code.

The idea is to flush the mm wide cache and tlb a priory and not bother
with multiple flushes if the batching isn't large enough.

This can be safely done since there cannot be any concurrency on this
mm, its either after the process died (exit) or in the middle of
execve where the thread switched to the new mm.

I think we actually *used* to do the final TLB flush from within the
context of the process that died. That doesn't seem to ever be the
case any more, but it does worry me a bit. Maybe a

   VM_BUG_ON(current->active_mm == mm);

or something for the fullmm case?

              Linus

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