sys: Remove $FreeBSD$: two-line .h pattern

Remove /^\s*\*\n \*\s+\$FreeBSD\$$\n/

spdx: The BSD-2-Clause-FreeBSD identifier is obsolete, drop -FreeBSD

The SPDX folks have obsoleted the BSD-2-Clause-FreeBSD identifier. Catch
up to that fact and revert to their recommended match of BSD-2-Clause.

Discussed with: pfg
MFC After: 3 days
Sponsored by: Netflix

lockprof: pass lock type as an argument instead of reading the spin flag

sys: clean up empty lines in .c and .h files

Add lockmgr(9) probes to the lockstat DTrace provider.

They follow the conventions set by rw and sx lock probes. There is
an additional lockstat:::lockmgr-disown probe.

Update lockstat(1) to report on contention and hold events for
lockmgr locks. Document the new probes in dtrace_lockstat.4, and
deduplicate some of the existing probe descriptions.

Reviewed by: mjg
MFC after: 1 week
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D21355

lockstat: track lockstat just like sdt probes

In particular flip the frequently tested var to bool.

Undo LOCK_PROFILING pessimisation after r313454 and r313455

With the option used to compile the kernel both sx and rw shared ops would
always go to the slow path which added avoidable overhead even when the
facility is disabled.

Furthermore the increased time spent doing uncontested shared lock acquire
would be bogusly added to total wait time, somewhat skewing the results.

Restore old behaviour of going there only when profiling is enabled.

This change is a no-op for kernels without LOCK_PROFILING (which is the
default).

sys/sys: further adoption of SPDX licensing ID tags.

Mainly focus on files that use BSD 2-Clause license, however the tool I
was using misidentified many licenses so this was mostly a manual - error
prone - task.

The Software Package Data Exchange (SPDX) group provides a specification
to make it easier for automated tools to detect and summarize well known
opensource licenses. We are gradually adopting the specification, noting
that the tags are considered only advisory and do not, in any way,
superceed or replace the license texts.

mtx: microoptimize lockstat handling in __mtx_lock_sleep

This saves a function call and multiple branches after the lock is acquired.

Make inline lockstat checks just inspect lockstat_enabled

There is no correctness issue and this lets the kernel just test one typically
false variable.

Implement LOCKSTAT_OOL_PROFILE_ENABLED

For use in uninlined locking primitives to decide whether lockstat
or profiling needs to be taken care of.

mtx: move lockstat handling out of inline primitives

Lockstat requires checking if it is enabled and if so, calling a 6 argument
function. Further, determining whether to call it on unlock requires
pre-reading the lock value.

This is problematic in at least 3 ways:
- more branches in the hot path than necessary
- additional cacheline ping pong under contention
- bigger code

Instead, check first if lockstat handling is necessary and if so, just fall
back to regular locking routines. For this purpose a new macro is introduced
(LOCKSTAT_PROFILE_ENABLED).

LOCK_PROFILING uninlines all primitives. Fold in the current inline lock
variant into the _mtx_lock_flags to retain the support. With this change
the inline variants are not used when LOCK_PROFILING is defined and thus
can ignore its existence.

This results in:
text data bss dec hex filename
22259667 1303208 4994976 28557851 1b3c21b kernel.orig
21797315 1303208 4994976 28095499 1acb40b kernel.patched

i.e. about 3% reduction in text size.

A remaining action is to remove spurious arguments for internal kernel
consumers.

Declare lockstat_enabled even when KDTRACE_HOOKS is not defined.

Reported by: bz
X-MFC-With: r285704

Consistently use a reader/writer flag for lockstat probes in rwlock(9) and
sx(9), rather than using the probe function name to determine whether a
given lock is a read lock or a write lock. Update lockstat(1) accordingly.

Implement the lockstat provider using SDT(9) instead of the custom provider
in lockstat.ko. This means that lockstat probes now have typed arguments and
will utilize SDT probe hot-patching support when it arrives.

Reviewed by: gnn
Differential Revision: https://reviews.freebsd.org/D2993

Pass the lock object to lockstat_nsecs() and return immediately if
LO_NOPROFILE is set. Some timecounter handlers acquire a spin mutex, and
we don't want to recurse if lockstat probes are enabled.

PR: 201642
Reviewed by: avg
MFC after: 3 days

Modify lockstat_nsecs() to just return unless lockstat probes are actually
enabled. The cost of a timecounter read can be quite significant, and the
problem became more apparent after r284297, since that change resulted in
a call to lockstat_nsecs() for each acquisition of an rwlock read lock.

PR: 201642
Reviewed by: avg
Tested by: Jason Unovitch
MFC after: 3 days
Differential Revision: https://reviews.freebsd.org/D3073

several lockstat improvements

0. For spin events report time spent spinning, not a loop count.
While loop count is much easier and cheaper to obtain it is hard
to reason about the reported numbers, espcially for adaptive locks
where both spinning and sleeping can happen.
So, it's better to compare apples and apples.

1. Teach lockstat about FreeBSD rw locks.
This is done in part by changing the corresponding probes
and in part by changing what probes lockstat should expect.

2. Teach lockstat that rw locks are adaptive and can spin on FreeBSD.

3. Report lock acquisition events for successful rw try-lock operations.

4. Teach lockstat about FreeBSD sx locks.
Reporting of events for those locks completely mirrors
rw locks.

5. Report spin and block events before acquisition event.
This is behavior documented for the upstream, so it makes sense to stick
to it. Note that because of FreeBSD adaptive lock implementations
both the spin and block events may be reported for the same acquisition
while the upstream reports only one of them.

Differential Revision: https://reviews.freebsd.org/D2727
Reviewed by: markj
MFC after: 17 days
Relnotes: yes
Sponsored by: ClusterHQ

Revert the approach for skipping lockstat_probe_func call when doing
lock_success/lock_failure, introduced in r228424, by directly skipping
in dtrace_probe.

This mainly helps in avoiding namespace pollution and thus lockstat.h
dependency by systm.h.

As an added bonus, this also helps in MFC case.
Reviewed by: avg
MFC after: 3 months (or never)
X-MFC: r228424

panic: add a switch and infrastructure for stopping other CPUs in SMP case

Historical behavior of letting other CPUs merily go on is a default for
time being. The new behavior can be switched on via
kern.stop_scheduler_on_panic tunable and sysctl.

Stopping of the CPUs has (at least) the following benefits:
- more of the system state at panic time is preserved intact
- threads and interrupts do not interfere with dumping of the system
state

Only one thread runs uninterrupted after panic if stop_scheduler_on_panic
is set. That thread might call code that is also used in normal context
and that code might use locks to prevent concurrent execution of certain
parts. Those locks might be held by the stopped threads and would never
be released. To work around this issue, it was decided that instead of
explicit checks for panic context, we would rather put those checks
inside the locking primitives.

This change has substantial portions written and re-written by attilio
and kib at various times. Other changes are heavily based on the ideas
and patches submitted by jhb and mdf. bde has provided many insights
into the details and history of the current code.

The new behavior may cause problems for systems that use a USB keyboard
for interfacing with system console. This is because of some unusual
locking patterns in the ukbd code which have to be used because on one
hand ukbd is below syscons, but on the other hand it has to interface
with other usb code that uses regular mutexes/Giant for its concurrency
protection. Dumping to USB-connected disks may also be affected.

PR: amd64/139614 (at least)
In cooperation with: attilio, jhb, kib, mdf
Discussed with: arch@, bde
Tested by: Eugene Grosbein <eugen@grosbein.net>,
gnn,
Steven Hartland <killing@multiplay.co.uk>,
glebius,
Andrew Boyer <aboyer@averesystems.com>
(various versions of the patch)
MFC after: 3 months (or never)

A new jail(8) with a configuration file, to replace the work currently done
by /etc/rc.d/jail.

Add the OpenSolaris dtrace lockstat provider. The lockstat provider
adds probes for mutexes, reader/writer and shared/exclusive locks to
gather contention statistics and other locking information for
dtrace scripts, the lockstat(1M) command and other potential
consumers.

Reviewed by: attilio jhb jb
Approved by: gnn (mentor)