r324803,r324836,r325469,r325706,r325917,r325918,r325919,r325920,r325921,
r325922,r325925,r325963,r326106,r326107,r326110,r326111,r326112,r326194,
r326195,r326196,r326197,r326198,r326199,r326200,r326237:

rwlock: perform the typically false td_rw_rlocks check later

Check if the lock is available first instead.

Sprinkle __read_frequently on few obvious places.

Note that some of annotated variables should probably change their types
to something smaller, preferably bit-sized.

mtx: drop the tid argument from _mtx_lock_sleep

tid must be equal to curthread and the target routine was already reading
it anyway, which is not a problem. Not passing it as a parameter allows for
a little bit shorter code in callers.

locks: partially tidy up waiting on readers

spin first instant of instantly re-readoing and don't re-read after
spinning is finished - the state is already known.

Note the code is subject to significant changes later.

locks: take the number of readers into account when waiting

Previous code would always spin once before checking the lock. But a lock
with e.g. 6 readers is not going to become free in the duration of once spin
even if they start draining immediately.

Conservatively perform one for each reader.

Note that the total number of allowed spins is still extremely small and is
subject to change later.

mtx: change MTX_UNOWNED from 4 to 0

The value is spread all over the kernel and zeroing a register is
cheaper/shorter than setting it up to an arbitrary value.

Reduces amd64 GENERIC-NODEBUG .text size by 0.4%.

mtx: fix up owner_mtx after r324609

Now that MTX_UNOWNED is 0 the test was alwayas false.

mtx: clean up locking spin mutexes

1) shorten the fast path by pushing the lockstat probe to the slow path
2) test for kernel panic only after it turns out we will have to spin,
in particular test only after we know we are not recursing

mtx: stop testing SCHEDULER_STOPPED in kabi funcs for spin mutexes

There is nothing panic-breaking to do in the unlock case and the lock
case will fallback to the slow path doing the check already.

rwlock: reduce lockstat branches in the slowpath

mtx: fix up UP build after r324778

mtx: implement thread lock fastpath

rwlock: fix up compilation without KDTRACE_HOOKS after r324787

rwlock: use fcmpset for setting RW_LOCK_WRITE_SPINNER

sx: avoid branches if in the slow path if lockstat is disabled

rwlock: avoid branches in the slow path if lockstat is disabled

locks: pull up PMC_SOFT_CALLs out of slow path loops

mtx: unlock before traversing threads to wake up

This shortens the lock hold time while not affecting corretness.
All the woken up threads end up competing can lose the race against
a completely unrelated thread getting the lock anyway.

rwlock: unlock before traversing threads to wake up

While here perform a minor cleanup of the unlock path.

sx: perform a minor cleanup of the unlock slowpath

No functional changes.

mtx: add missing parts of the diff in r325920

Fixes build breakage.

locks: fix compilation issues without SMP or KDTRACE_HOOKS

locks: remove the file + line argument from internal primitives when not used

The pair is of use only in debug or LOCKPROF kernels, but was passed (zeroed)
for many locks even in production kernels.

While here whack the tid argument from wlock hard and xlock hard.

There is no kbi change of any sort - "external" primitives still accept the
pair.

locks: pass the found lock value to unlock slow path

This avoids an explicit read later.

While here whack the cheaply obtainable 'tid' argument.

rwlock: don't check for curthread's read lock count in the fast path

rwlock: unbreak WITNESS builds after r326110

sx: unbreak debug after r326107

An assertion was modified to use the found value, but it was not updated to
handle a race where blocked threads appear after the entrance to the func.

Move the assertion down to the area protected with sleepq lock where the
lock is read anyway. This does not affect coverage of the assertion and
is consistent with what rw locks are doing.

rwlock: stop re-reading the owner when going to sleep

locks: retry turnstile/sleepq loops on failed cmpset

In order to go to sleep threads set waiter flags, but that can spuriously
fail e.g. when a new reader arrives. Instead of unlocking everything and
looping back, re-evaluate the new state while still holding the lock necessary
to go to sleep.

sx: change sunlock to wake waiters up if it locked sleepq

sleepq is only locked if the curhtread is the last reader. By the time
the lock gets acquired new ones could have arrived. The previous code
would unlock and loop back. This results spurious relocking of sleepq.

This is a step towards xadd-based unlock routine.

rwlock: add __rw_try_{r,w}lock_int

rwlock: fix up compilation of the previous change

commmitted wrong version of the patch

Convert in-kernel thread_lock_flags calls to thread_lock when debug is disabled

The flags argument is not used in this case.

Add the missing lockstat check for thread lock.

rw: fix runlock_hard when new readers show up

When waiters/writer spinner flags are set no new readers can show up unless
they already have a different rw rock read locked. The change in r326195 failed
to take that into account - in presence of new readers it would spin until
they all drain, which would be lead to trouble if e.g. they go off cpu and
can get scheduled because of this thread.