On 06/08/2017 10:30 PM, Michal Hocko wrote:

But I guess you are primary after syncing the preemptive mode for 64 and
32b systems, right? I agree that having a different model is more than
unfortunate because 32b gets much less testing coverage and so a risk of
introducing a new bug is just a matter of time. Maybe we should make
pte_offset_map disable preemption and currently noop pte_unmap to
preempt_enable. The overhead should be pretty marginal on x86_64 but not
all arches have per-cpu preempt count. So I am not sure we really want
to add this to just for the debugging purposes...

I think adding that overhead for everyone would be unfortunate. It would
be acceptable, if it was done only for the config option that enables
the might_sleep() checks (CONFIG_DEBUG_ATOMIC_SLEEP?)

Vlastimil

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