MFC r344855 (by jhb):

Drop "All rights reserved" from my copyright statements.

Reviewed by: rgrimes
Differential Revision: https://reviews.freebsd.org/D19485

MFC r349220: Add wakeup_any(), cheaper wakeup_one() for taskqueue(9).

wakeup_one() and underlying sleepq_signal() spend additional time trying
to be fair, waking thread with highest priority, sleeping longest time.
But in case of taskqueue there are many absolutely identical threads, and
any fairness between them is quite pointless. It makes even worse, since
round-robin wakeups not only make previous CPU affinity in scheduler quite
useless, but also hide from user chance to see CPU bottlenecks, when
sequential workload with one request at a time looks evenly distributed
between multiple threads.

This change adds new SLEEPQ_UNFAIR flag to sleepq_signal(), making it wakeup
thread that went to sleep last, but no longer in context switch (to avoid
immediate spinning on the thread lock). On top of that new wakeup_any()
function is added, equivalent to wakeup_one(), but setting the flag.
On top of that taskqueue(9) is switchied to wakeup_any() to wakeup its
threads.

As result, on 72-core Xeon v4 machine sequential ZFS write to 12 ZVOLs
with 16KB block size spend 34% less time in wakeup_any() and descendants
then it was spending in wakeup_one(), and total write throughput increased
by ~10% with the same as before CPU usage.

Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

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

Misc mdoc fixes:

- Remove superfluous paragraph macros.
- Remove/fix empty or incorrect macros.
- Sort sections into conventional order.
- Terminate quoted strings properly.
- Remove EOL whitespace.

Bump .Dd

Approved by: kevlo

Reflect the chanages in sleepqueue.h and subr_sleepqueue.c

- Priority argument is introduced to sleepq_*wait* in r177085
- sleepq_calc_signal_retval is removed from implementation
- sleepq_catch_signals is internal now

Differential Revision: https://reviews.freebsd.org/D794
Reviewed by: jhb
Approved by: jhb

MFcalloutng:
Dcoument the new functions added to condvar(9), sleep(9), sleepqueue(9)
KPIs. Also document recent changes in timeout(9) and eventtimers(4).

- change "is is" to "is" or "it is"
- change "the the" to "the"

Approved by: lstewart
Approved by: sahil (mentor)
MFC after: 3 days

Introduce the new kernel thread called "deadlock resolver".
While the name is pretentious, a good explanation of its targets is
reported in this 17 months old presentation e-mail:
http://lists.freebsd.org/pipermail/freebsd-arch/2008-August/008452.html

In order to implement it, the sq_type in sleepqueues is mandatory and not
only compiled along with INVARIANTS option. Additively, a new sleepqueue
function, sleepq_type() is added, returning the type of the sleepqueue
linked to a wchan.
Three new sysctls are added in order to configure the thread:
debug.deadlkres.slptime_threshold
debug.deadlkres.blktime_threshold
debug.deadlkres.sleepfreq

rappresenting the thresholds for sleep and block time that will lead to
a deadlock matching (when exceeded), while the sleepfreq rappresents the
number of seconds between 2 consecutive thread runnings.
In order to enable the deadlock resolver thread recompile your kernel
with the option DEADLKRES.

Reviewed by: jeff
Tested by: pho, Giovanni Trematerra
Sponsored by: Nokia Incorporated, Sandvine Incorporated
MFC after: 2 weeks

Document PBDRY and SLEEPQ_STOP_ON_BDRY.

Requested and reviewed by: attilio
MFC after: 3 days

In current code, threads performing an interruptible sleep (on both
sxlock, via the sx_{s, x}lock_sig() interface, or plain lockmgr), will
leave the waiters flag on forcing the owner to do a wakeup even when if
the waiter queue is empty.
That operation may lead to a deadlock in the case of doing a fake wakeup
on the "preferred" (based on the wakeup algorithm) queue while the other
queue has real waiters on it, because nobody is going to wakeup the 2nd
queue waiters and they will sleep indefinitively.

A similar bug, is present, for lockmgr in the case the waiters are
sleeping with LK_SLEEPFAIL on. In this case, even if the waiters queue
is not empty, the waiters won't progress after being awake but they will
just fail, still not taking care of the 2nd queue waiters (as instead the
lock owned doing the wakeup would expect).

In order to fix this bug in a cheap way (without adding too much locking
and complicating too much the semantic) add a sleepqueue interface which
does report the actual number of waiters on a specified queue of a
waitchannel (sleepq_sleepcnt()) and use it in order to determine if the
exclusive waiters (or shared waiters) are actually present on the lockmgr
(or sx) before to give them precedence in the wakeup algorithm.
This fix alone, however doesn't solve the LK_SLEEPFAIL bug. In order to
cope with it, add the tracking of how many exclusive LK_SLEEPFAIL waiters
a lockmgr has and if all the waiters on the exclusive waiters queue are
LK_SLEEPFAIL just wake both queues.

The sleepq_sleepcnt() introduction and ABI breakage require
__FreeBSD_version bumping.

Reported by: avg, kib, pho
Reviewed by: kib
Tested by: pho

Document the new return values for sleepq_abort(), sleepq_broadcast(), and
sleepq_signal().

Prodded by: attilio

- Change the description of sleepq_add(), sleepq_broadcast() and
sleepq_signal() to reflect recent changes

Submitted by: attilio
Approved by: re (bmah)

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.

Document SLEEPQ_PAUSE.

Change sleepq_add(9) argument from 'struct mtx *' to 'struct lock_object *',
which allows to use it with different kinds of locks. For example it allows
to implement Solaris conditions variables which will be used in ZFS port on
top of sx(9) locks.

Reviewed by: jhb

Bring API documentation for sleepqueue(9) in sync with the code
in -current.

Reviewed by: ru

Scheduled mdoc(7) sweep.

Catch up to recent API changes including the removal of the signal_caught
argument to sleepq_timedwait() and the enhancements to the flags argument
passed to sleepq_add().

Spelling fixes.

Tiny markup fixes.

Rewrite sleepqueue manpage to catch up to the new sleep queue interface.

mdoc(7) police: finish up the "proc" -> "thread" conversion.

Update function definitions and required include files to reflect
the current state of the system.

Approved by: alfred

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

Add 2001 to copyright.

mdoc(7) police: fixed some minor formatting/spelling errors.

Document the current organization and helper functions used to implement
the sleep queues used by msleep/wakeup and friends.

Submitted by: sheldonh