- Replace 'process' with 'thread' everywhere.
- Update several places to note that that the fact that default mutexes
may adaptively spin isn't necessarily MD, but is just part of the
implementation as a whole.
- Clarify the text about MTX_SPIN mutexes only being appropriate for
INTR_FAST interrupts or other low level scheduler code to make the
jargon more FreeBSD-ish rather than BSD/OS-ish.
- Also, note that it is possible that interrupts aren't blocked but just
deferred when a spin lock is held (the whole blocked vs. deferred bit is
an MD implementation detail).
- Remove statements saying that spin locks must be released in the exact
opposite order that they were acquired. This stopped being true several
years ago when we first added critical sections that stored their state
in the current thread rather than in struct mtx.
- Note that a mutex must be initialized before it is passed to any other
mutex function, not just mtx_lock.
- Clarify that mtx_trylock() only operates on MTX_DEF mutexes.
- Simplify the text about possible preemption during a mtx_unlock().
- Use complete English sentences in place of phrases in a few places.
- Clarify that it isn't ever safe to sleep with a mutex held. The kernel
tends to panic when you do that.
Requested by: scottl (7)
MFC after: 3 days
a30c1e0a0b