Merge fresh head.

sync from head

Another NFS SIGSTOP related fix: Ignore thread suspend requests due to
SIGSTOP if stop signals are currently deferred. This can occur if a
process is stopped via SIGSTOP while a thread is running or

Another NFS SIGSTOP related fix: Ignore thread suspend requests due to
SIGSTOP if stop signals are currently deferred. This can occur if a
process is stopped via SIGSTOP while a thread is running or runnable
but before it has set TDF_SBDRY.

Tested by: pho
Reviewed by: kib
MFC after: 1 week

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IFC @247348.

Fix a few typos.

MFC @ r241285

IFC @ r242684

Sync from head

Make the updates of the tid ring buffer' head and tail pointers
explicit by moving them into separate statements from the buffer
element accesses.

Requested by: jhb
MFC after: 3 days

Do not skip two elements of the tid_buffer when reusing the buffer
slot. This eventually results in exhaustion of the tid space, causing
new threads get tid -1 as identifier.

The bad effect of havin

Do not skip two elements of the tid_buffer when reusing the buffer
slot. This eventually results in exhaustion of the tid space, causing
new threads get tid -1 as identifier.

The bad effect of having the thread id equal to -1 is that
UMTX_OP_UMUTEX_WAIT returns EFAULT for a lock owned by such thread,
because casuword cannot distinguish between literal value -1 read from
the address and -1 returned as an indication of faulted
access. _thr_umutex_lock() helper from libthr does not check for
errors from _umtx_op_err(2), causing an infinite loop in
mutex_lock_sleep().

We observed the JVM processes hanging and consuming enormous amount of
system time on machines with approximately 100 days uptime.

Reported by: Mykola Dzham <freebsd levsha org ua>
MFC after: 1 week

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Remove all the checks on curthread != NULL with the exception of some MD
trap checks (eg. printtrap()).

Generally this check is not needed anymore, as there is not a legitimate
case where curthread

Remove all the checks on curthread != NULL with the exception of some MD
trap checks (eg. printtrap()).

Generally this check is not needed anymore, as there is not a legitimate
case where curthread != NULL, after pcpu 0 area has been properly
initialized.

Reviewed by: bde, jhb
MFC after: 1 week

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A few whitespace and comment fixes.

Merge head r233826 through r240095.

Fix grammar.

Submitted by: jh
MFC after: 1 week

Add a sysctl kern.pid_max, which limits the maximum pid the system is
allowed to allocate, and corresponding tunable with the same
name. Note that existing processes with higher pids are left intact.

Add a sysctl kern.pid_max, which limits the maximum pid the system is
allowed to allocate, and corresponding tunable with the same
name. Note that existing processes with higher pids are left intact.

MFC after: 1 week

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IFC @238412.

IFC @ r238370

Merge head r233826 through r236557.

Add a rangelock implementation, intended to be used to range-locking
the i/o regions of the vnode data space. The implementation is quite
simple-minded, it uses the list of the lock requests, ordered

Add a rangelock implementation, intended to be used to range-locking
the i/o regions of the vnode data space. The implementation is quite
simple-minded, it uses the list of the lock requests, ordered by
arrival time. Each request may be for read or for write. The
implementation is fair FIFO.

MFC after: 2 month

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IFC @ r236291.
Diff reductions to the enclosure driver made in r235911.

Merge head r233826 through r236168.

Implement the DTrace sched provider. This implementation aims to be
compatible with the sched provider implemented by Solaris and its open-
source derivatives. Full documentation of the sched provi

Implement the DTrace sched provider. This implementation aims to be
compatible with the sched provider implemented by Solaris and its open-
source derivatives. Full documentation of the sched provider can be found
on Oracle's DTrace wiki pages.

Note that for compatibility with scripts originally written for Solaris,
serveral probes are defined that will never fire. These probes are defined
to fire when Solaris-specific features perform certain actions. As these
features are not present in FreeBSD, the probes can never fire.

Also, I have added a two probes that are not defined in Solaris, lend-pri
and load-change. These probes have been added to make it possible to
collect schedgraph data with DTrace.

Finally, a few probes are defined in Solaris to take a cpuinfo_t *
argument. As it was not immediately clear to me how to translate that to
FreeBSD, currently those probes are passed NULL in place of a cpuinfo_t *.

Sponsored by: Sandvine Incorporated
MFC after: 2 weeks

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IFC @230489 (pending review).

IFC to head to catch up the bhyve branch

Approved by: grehan@

Some small fixes to CPU accounting for threads:
- Only initialize the per-cpu switchticks and switchtime in sched_throw()
for the very first context switch on APs during boot. This avoids a
smal

Some small fixes to CPU accounting for threads:
- Only initialize the per-cpu switchticks and switchtime in sched_throw()
for the very first context switch on APs during boot. This avoids a
small gap between the middle of thread_exit() and sched_throw() where
time is not accounted to any thread.
- In thread_exit(), update the timestamp bookkeeping to track the changes
to mi_switch() introduced by td_rux so that the code once again matches
the comment claiming it is mimicing mi_switch(). Specifically, only
update the per-thread stats directly and depend on ruxagg() to update
p_rux rather than adjusting p_rux directly. While here, move the
timestamp bookkeeping as late in the function as possible.

Reviewed by: bde, kib
MFC after: 1 week

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