K 10
svn:author
V 3
cem
K 8
svn:date
V 27
2020-07-24T17:32:10.029510Z
K 7
svn:log
V 805
Use SMR to provide safe unlocked lookup for pctries from SMR zones

Adapt r358130, for the almost identical vm_radix, to the pctrie subsystem.
Like that change, the tree is kept correct for readers with store barriers
and careful ordering.  Existing locks serialize writers.

Add a PCTRIE_DEFINE_SMR() wrapper that takes an additional smr_t parameter
and instantiates a FOO_PCTRIE_LOOKUP_UNLOCKED() function, in addition to the
usual definitions created by PCTRIE_DEFINE().

Interface consumers will be introduced in later commits.

As future work, it might be nice to add vm_radix algorithms missing from
generic pctrie to the pctrie interface, and then adapt vm_radix to use
pctrie.

Reported by:	Attilio
Reviewed by:	markj
Sponsored by:	Isilon
Differential Revision:	https://reviews.freebsd.org/D25781

END