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

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

Reclaim unused ithread priorities for user time-sharing threads.

Leave one band of ithread priorities available below PI_SOFT for
demoted ithreads but reclaim additional ithread priorities for use by
user time-sharing threads. This is an ABI change in that PZERO moves
up so old ps and top binaries will not format priorities correctly on
newer kernels, but that is a cosmetic rather than functional change.

Reviewed by: kib, markj
Sponsored by: Netflix
Differential Revision: https://reviews.freebsd.org/D35647

Collapse interrupt thread priorities.

Allow high priority hardware interrupts to run at PI_REALTIME via
INTR_TYPE_CLK, but collapse all other hardware interrupt threads to
the next priority level (PI_INTR). Collapse all SWI priorities to
the same priority level (PI_SOFT) just below PI_INTR.

Reviewed by: kib, markj
Sponsored by: Netflix
Differential Revision: https://reviews.freebsd.org/D35646

Run softclock threads at a hardware ithread priority.

Add a new PI_SOFTCLOCK for use by softclock threads. Currently this
maps to PI_AV which is the second-highest ithread priority.

Reviewed by: mav, kib
Sponsored by: Netflix
Differential Revision: https://reviews.freebsd.org/D33693

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.

sys/sys: minor spelling fixes.

While the changes are minor, these headers are very visible.

MFC after: 2 weeks

Use a name instead of a magic number for kern_yield(9) when the priority
should not change. Fetch the td_user_pri under the thread lock. This
is probably not necessary but a magic number also seems preferable to
knowing the implementation details here.

Requested by: Jason Behmer < jason DOT behmer AT isilon DOT com >

Rework realtime priority support:
- Move the realtime priority range up above kernel sleep priorities and
just below interrupt thread priorities.
- Contract the interrupt and kernel sleep priority ranges a bit so that
the timesharing priority band can be increased. The new timeshare range
is now slightly larger than the old realtime + timeshare ranges.
- Change the ULE scheduler to no longer use realtime priorities for
interactive threads. Instead, the larger timeshare range is now split
into separate subranges for interactive and non-interactive ("batch")
threads. The end result is that interactive threads and non-interactive
threads still use the same priority ranges as before, but realtime
threads now have a separate, dedicated priority range.
- Do not modify the priority of non-timeshare threads in sched_sleep()
or via cv_broadcastpri(). Realtime and idle priority threads will
no longer have their priorities affected by sleeping in the kernel.

Reviewed by: jeff

- Retire some unused ithread priorities: PI_TTYHIGH, PI_TAPE, and
PI_DISKLOW. While here, rename PI_TTYLOW to PI_TTY.
- Add a macro PI_SWI() that takes a SWI_* constant as an argument and
returns the suitable thread priority.

Retire PCONFIG and leave the priority of thread0 alone when waiting for
interrupt config hooks to execute.

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

- Import the HEAD csup code which is the basis for the cvsmode work.

Replace (name) with Henric Vestergaard Draboel since it was clear that
this was just cut N paste and '(name)' doesn't make any sense. If
someone knows how to contact Mr. Draboel, please let me know.

/* -> /*- for license, minor formatting changes

style(9) the structure definitions.

Implement a unified run queue and adjust priority levels accordingly.

- All processes go into the same array of queues, with different
scheduling classes using different portions of the array. This
allows user processes to have their priorities propogated up into
interrupt thread range if need be.
- I chose 64 run queues as an arbitrary number that is greater than
32. We used to have 4 separate arrays of 32 queues each, so this
may not be optimal. The new run queue code was written with this
in mind; changing the number of run queues only requires changing
constants in runq.h and adjusting the priority levels.
- The new run queue code takes the run queue as a parameter. This
is intended to be used to create per-cpu run queues. Implement
wrappers for compatibility with the old interface which pass in
the global run queue structure.
- Group the priority level, user priority, native priority (before
propogation) and the scheduling class into a struct priority.
- Change any hard coded priority levels that I found to use
symbolic constants (TTIPRI and TTOPRI).
- Remove the curpriority global variable and use that of curproc.
This was used to detect when a process' priority had lowered and
it should yield. We now effectively yield on every interrupt.
- Activate propogate_priority(). It should now have the desired
effect without needing to also propogate the scheduling class.
- Temporarily comment out the call to vm_page_zero_idle() in the
idle loop. It interfered with propogate_priority() because
the idle process needed to do a non-blocking acquire of Giant
and then other processes would try to propogate their priority
onto it. The idle process should not do anything except idle.
vm_page_zero_idle() will return in the form of an idle priority
kernel thread which is woken up at apprioriate times by the vm
system.
- Update struct kinfo_proc to the new priority interface. Deliberately
change its size by adjusting the spare fields. It remained the same
size, but the layout has changed, so userland processes that use it
would parse the data incorrectly. The size constraint should really
be changed to an arbitrary version number. Also add a debug.sizeof
sysctl node for struct kinfo_proc.