Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

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

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

Approved by: re (implicit)

Switch to the event timers infrastructure. This includes:
o Setting td_intr_frame to the XIVs trap frame because it's referenced
by the ET event handler.
o Signal EOI to the CPU before calling the registered XIV handlers.
This prevents lost ITC interrupts, which cause starvation in one-shot
mode.
o Adding support for IPI_HARDCLOCK with corresponding per-CPU counters.
o Have the APs call cpu_initclocks() so as to limited the scattering of
clock related initialization. cpu_initclocks() calls the <self>_bsp()
or <self>_ap() version accordingly.
o Uncomment the ET clock handling in cpu_idle().
o Update the DDB 'show pcpu' output for the new MD fields.
o Entirely rewritten ia64_ih_clock(). Note that we don't create as many
clock XIVs as we have CPUs, as is done on PowerPC. It doesn't scale.
We can only have 240 XIVs and we can have more CPUs than that. There's
a single intrcnt index for the cumulative clock ticks and we keep per
CPU counts in the PCPU stats structure.
o Register the ITC by hooking SI_SUB_CONFIGURE (2nd order).

Open issues:
o Clock interrupts can still be lost. Some tweaking is still necessary.

Thanks to: mav@ for his support, feedback and explanations.

ET stats while committing:
eris% sysctl machdep.cpu | grep nclks

machdep.cpu.0.nclks: 24007
machdep.cpu.1.nclks: 22895
machdep.cpu.2.nclks: 13523
machdep.cpu.3.nclks: 9342
machdep.cpu.4.nclks: 9103
machdep.cpu.5.nclks: 9298
machdep.cpu.6.nclks: 10039
machdep.cpu.7.nclks: 9479
eris% vmstat -i | grep clock
clock 108599 50

Change region 4 to be part of the kernel. This serves 2 purposes:
1. The PBVM is in region 4, so if we want to make use of it, we
need region 4 freed up.
2. Region 4 and above cannot be represented by an off_t by virtue
of that type being signed. This is problematic for truss(1),
ktrace(1) and other such programs.

Remove unused includes of <sys/mutex.h> and <machine/mutex.h>.

- Adjust the whitespace for the lines that output fields in 'show pcpu' in
DDB so that all the fields line up.
- Print out the tid of the per-CPU idlethread instead of the pid since
the idle process is now shared across all idle threads.

MFC after: 1 month

Print MD fields in the pcpu to aid debugging.

opt_* headers are included using the quoted form.

Break out stack(9) from ddb(4):

- Introduce per-architecture stack_machdep.c to hold stack_save(9).
- Introduce per-architecture machine/stack.h to capture any common
definitions required between db_trace.c and stack_machdep.c.
- Add new kernel option "options STACK"; we will build in stack(9) if it is
defined, or also if "options DDB" is defined to provide compatibility
with existing users of stack(9).

Add new stack_save_td(9) function, which allows the capture of a stacktrace
of another thread rather than the current thread, which the existing
stack_save(9) was limited to. It requires that the thread be neither
swapped out nor running, which is the responsibility of the consumer to
enforce.

Update stack(9) man page.

Build tested: amd64, arm, i386, ia64, powerpc, sparc64, sun4v
Runtime tested: amd64 (rwatson), arm (cognet), i386 (rwatson)

Print instruction stops to improve analysis of dependency
violations.

MFC after: 1 week

Add option EXCEPTION_TRACING, which enables KTR-like functionality
for processor interruptions. This is especially useful to track
unexpected nested TLB faults.

Approved by: re (blanket)

Synchronize the instruction cache after writing to memory. This is
needed for breakpoints to work.

Simplify the pager support in DDB. Allowing different db commands to
install custom pager functions didn't actually happen in practice (they
all just used the simple pager and passed in a local quit pointer). So,
just hardcode the simple pager as the only pager and make it set a global
db_pager_quit flag that db commands can check when the user hits 'q' (or a
suitable variant) at the pager prompt. Also, now that it's easy to do so,
enable paging by default for all ddb commands. Any command that wishes to
honor the quit flag can do so by checking db_pager_quit. Note that the
pager can also be effectively disabled by setting $lines to 0.

Other fixes:
- 'show idt' on i386 and pc98 now actually checks the quit flag and
terminates early.
- 'show intr' now actually checks the quit flag and terminates early.

Merge db_interface.c and db_trace.c into db_machdep.c.