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 r242992: Avoid an ambiguous reference to mtx_lock(9).

MFC r233648:
Remove trailing whitespace per mdoc lint warning

Approved by: cperciva (implicit)

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

Approved by: re (implicit)

The NetBSD Foundation has granted permission to remove clause 3 and 4 from
their software.

Obtained from: NetBSD

Allow threads to atomically release rw and sx locks while waiting for an
event. Locking primitives that support this (mtx, rw, and sx) now each
include their own foo_sleep() routine.
- Rename msleep() to _sleep() and change it's 'struct mtx' object to a
'struct lock_object' pointer. _sleep() uses the recently added
lc_unlock() and lc_lock() function pointers for the lock class of the
specified lock to release the lock while the thread is suspended.
- Add wrappers around _sleep() for mutexes (mtx_sleep()), rw locks
(rw_sleep()), and sx locks (sx_sleep()). msleep() still exists and
is now identical to mtx_sleep(), but it is deprecated.
- Rename SLEEPQ_MSLEEP to SLEEPQ_SLEEP.
- Rewrite much of sleep.9 to not be msleep(9) centric.
- Flesh out the 'RETURN VALUES' section in sleep.9 and add an 'ERRORS'
section.
- Add __nonnull(1) to _sleep() and msleep_spin() so that the compiler will
warn if you try to pass a NULL wait channel. The functions already have
a KASSERT to that effect.

Start sentences from a capital letter.

Submitted by: Joel Dahl

Mechanically kill hard sentence breaks and double whitespaces.

english(4) police.

mdoc(7) police: tidy up formatting.

Slight changes to reflect some of the changes in -current.
mi_switch(9) is still wildly innacurate. I suggest that every kernel
developer takes 20 minutes a day for the next few days and updates one or
two of his favourite chapter 9 man pages as they are now WAY out of date
in general. I will add a couple of KSE related pages soon.

mdoc(7) police: Use the new .In macro for #include statements.

mdoc(7) police:

Avoid using parenthesis enclosure macros (.Pq and .Po/.Pc) with plain text.
Not only this slows down the mdoc(7) processing significantly, but it also
has an undesired (in this case) effect of disabling hyphenation within the
entire enclosed block.

mdoc(7) police: removed HISTORY info from the .Os call.

mdoc(7) police: split punctuation characters + misc fixes.

Catch up to the new way that the scheduling code works since the original
SMPng commit. Also document the new cpu_throw function (currently only
on i386).

Reviewed by: sheldonh

The prototype for cpu_switch() was changed in revision 1.111 of
<sys/proc.h>

PR: 24311
Submitted by: Robert Drehmel <robert@gizmo.quizbot.org>

mdoc(7) police: use canonical form of .Dd macro.

Remove single-space hard sentence breaks. These degrade the quality
of the typeset output, tend to make diffs harder to read and provide
bad examples for new-comers to mdoc.

$Id$ -> $FreeBSD$

Add $Id$, to make it simpler for members of the translation teams to
track.

The $Id$ line is normally at the bottom of the main comment block in the
man page, separated from the rest of the manpage by an empty comment,
like so;

.\" $Id$
.\"

If the immediately preceding comment is a @(#) format ID marker than the
the $Id$ will line up underneath it with no intervening blank lines.
Otherwise, an additional blank line is inserted.

Approved by: bde

Typo fix: sq --> qs

Fixed #include and/or prototype bugs in synopsis.

Minor mdoc fixes.

Add mi_switch.9. It documents the kernel mi_switch() and cpu_switch()
context switching functions.

Obtained from: NetBSD (renamed from ctxsw.9)