I'm tired of the fmut/pmut shenanigans. This consolidates both under one
lock; I'm not convinced there are any significant performance
differences with this approach since we're literally just protecting map
juggling...
- The locking goes away when we were already under an appropriate fmut
lock.
- Where we had fmut.RLock()+pmut.Lock() it gets upgraded to an
fmut.Lock().
- Otherwise s/pmut/fmut/.
In order to avoid diff noise for an important change I did not do the
following cleanups, which will be filed in a PR after this one, if
accepted:
- Renaming fmut to just mut
- Renaming methods that refer to being "PRLocked" and stuff like that
- Removing the no longer relevant deadlock detector
- Comments referring to pmut and locking sequences...