Mark Johnston 1587dc37fa Have arm64's pmap_fault() handle WnR faults on dirty PTEs.
If we take a WnR permission fault on a managed, writeable and dirty
PTE, simply return success without calling the main fault handler.  This
situation can occur if multiple threads simultaneously access a clean
writeable mapping and trigger WnR faults; losers of the race to mark the
PTE dirty would end up calling the main fault handler, which had no work
to do.

Reported by:	alc
Reviewed by:	alc
MFC with:	r350004
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D21097
2019-07-29 21:21:53 +00:00
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