K 10
svn:author
V 3
jhb
K 8
svn:date
V 27
2018-11-05T22:54:03.709846Z
K 7
svn:log
V 502
Add a custom implementation of cpu_lock_delay() for x86.

Avoid using DELAY() since it can try to use spin locks on CPUs without
a P-state invariant TSC.  For cpu_lock_delay(), always use the TSC if
it exists (even if it is not P-state invariant) to delay for a
microsecond.  If the TSC does not exist, read from I/O port 0x84 to
delay instead.

PR:		228768
Reported by:	Roger Hammerstein <cheeky.m@live.com>
Reviewed by:	kib
MFC after:	3 days
Differential Revision:	https://reviews.freebsd.org/D17851

END