Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

MFC 233422,233680,233681,237619,239904,249373,252346,252379,252423:
Sync locking(9) with HEAD. The only change not merged is that 9 still
supports !MPSAFE filesystems.

MFC r233648:
Remove trailing whitespace per mdoc lint warning

Approved by: cperciva (implicit)

MFC r236237:

Fix lock interaction table for rmlocks - by default they cannot sleep,
just like rwlocks.

MFC r235693:

Typo and mdoc(7) style fixes.

PR: 168117

MFC r235319:

Remove duplicate words in mdoc(7) pages.

PR: 167810

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

Xref BUS_SETUP_INTR(9) and locking(9).

rmlock(9) two additions and one change/fix:
- add rm_try_rlock().
- add RM_SLEEPABLE to use sx(9) as the back-end lock in order to sleep while
holding the write lock.
- change rm_noreadtoken to a cpu bitmask to indicate which CPUs need to go
through the lock/unlock in order to synchronize. As a side effect, this
also avoids IPI to CPUs without any readers during rm_wlock.

Discussed with: ups@, rwatson@ on arch@
Sponsored by: Isilon Systems, Inc.

s/ithread/interrupt thread/

Fix a bunch of typos and spelling mistakes.

Some rewording and language fixes.

PR: docs/136918, docs/134074
Submitted by: Ben Kaduk <kaduk at mit dot edu>, Haven Hash <havenster at gmail dot com>

Remove list of locking primitives, which is kind of redundant, move
information about witness(9) to the section about interactions, and
expand 'contexts' table.

Start sentences with a new line.

Submitted by: brueffer

Improve description for Giant and mention blocking inside interrupt threads.

Cosmetic fixes.

Add description of bounded sleep vs unbounded sleep (aka blocking). Move
rules into their own section.

Improve descriptions, remove turnstiles (since, from what I understand,
they are only used to implement other synchronization primitives), tweak
formatting.

Initial checkin for rmlock (read mostly lock) a multi reader single writer
lock optimized for almost exclusive reader access. (see also rmlock.9)

TODO:
Convert to per cpu variables linkerset as soon as it is available.
Optimize UP (single processor) case.

Corrections and clarifications

Approved by: re (bmah)

Remove duplicate xref and add missing commas.

PR: 113891
Submitted by: pluknet <pluknet@gmail.com>
Approved by: re (blanket)

Markup fixes.

Giant is special. How do I love thee? Let me count the ways?

errr, I mean "Enumerate how the giant lock differs from other locks"

Please let me know if I missed any. Or misrepresented any...

Reviewed by: ssouhlal@

- Remove an unneeded comma
- Remove a redundant .Xc
- Spell "Largely" as it should.

More corrections, this time from Wojciech Koszek

Spelling and whitespace fixes from Dunne Whitty

fix braino in markup.

More suggestions from pjd.

Some comments from pjd

Add locking.9
This is supposed to be a brief overview of the locking primatives.
It is not yet complete and contains many place-holders for information
I do not know.

The locking is getting so diverse that I've lost track of it all.
We need this page to keep outselves in sync with what the primitives do.

note.. not part of the build yet.