Make the inlines static to avoid kernel build failure with Clang 11 on i386.
(The issue was not observed with Clang 10, currently in tree; reproduction
depends on compiler inlining choices.)
The compiler may choose not to inline 'bare' C inlines, and in that case
expects a symbol of the same name will be available. It does not
automatically define that symbol at use, because of traditional C linking
semantics. (In contrast, C++ does define it, and then deduplicates redundant
definitions at link). As we do not instantiate the C99 inline ('extern
inline ...;'), the linker errors with "undefined symbol."
Reported by: dim
Tested by: dim
Fixes: r364219
Add prng(9) as a replacement for random(9) in the kernel.
There are two major differences from random(9) and random(3):
- General prng(9) APIs (prng32(9), etc) do not guarantee an
implementation or particular sequence; they should not be used for
repeatable simulations.
- However, specific named API families are also exposed (for now: PCG),
and those are expected to be repeatable (when so-guaranteed by the named
algorithm).
Some minor differences from random(3) and earlier random(9):
- PRNG state for the general prng(9) APIs is per-CPU; this eliminates
contention on PRNG state in SMP workloads. Each PCPU generator in an
SMP system produces a unique sequence.
- Better statistical properties than the Park-Miller ("minstd") PRNG
(longer period, uniform distribution in all bits, passes
BigCrush/PractRand analysis).
- Faster than Park-Miller ("minstd") PRNG -- no division is required to
step PCG-family PRNGs.
For now, random(9) becomes a thin shim around prng32(). Eventually I
would like to mechanically switch consumers over to the explicit API.
Reviewed by: kib, markj (previous version both)
Discussed with: markm
Differential Revision: https://reviews.freebsd.org/D25916
