Minor ULE changes and optimizations

[John Baldwin]

On Thursday, February 26, 2015 06:23:16 AM Harrison Grundy wrote:
> https://reviews.freebsd.org/D1969
> This allows a non-migratable thread to pin itself to a CPU if it is
> already running on that CPU.
> 
> I've been running these patches for the past week or so without issue.
> Any additional testing or comments would be greatly appreciated.

Can you explain the reason / use case for this?  This seems to be allowing an 
API violation.  sched_pin() was designed to be a lower-level API than 
sched_bind(), so you wouldn't call sched_bind() if you were already pinned.  
In addition, sched_pin() is sometimes used by code that assumes it won't 
migrate until sched_unpin() (e.g. temporary mappings inside an sfbuf).  If you 
allow sched_bind() to move a thread that is pinned you will allow someone to 
unintentionally break those sort of things instead of getting an assertion 
failure panic.

-- 
John Baldwin