libthr: remove explicit sys/cdefs.h includes

Sponsored by: The FreeBSD Foundation
MFC after: 1 week

Remove $FreeBSD$: one-line .c pattern

Remove /^[\s*]*__FBSDID\("\$FreeBSD\$"\);?\s*\n/

Merge ^/head r325842 through r325998.

spdx: initial adoption of licensing ID tags.

The Software Package Data Exchange (SPDX) group provides a specification
to make it easier for automated tools to detect and summarize well known
opensou

spdx: initial adoption of licensing ID tags.

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.

Special thanks to Wind River for providing access to "The Duke of
Highlander" tool: an older (2014) run over FreeBSD tree was useful as a
starting point.

Initially, only tag files that use BSD 4-Clause "Original" license.

RelNotes: yes
Differential Revision: https://reviews.freebsd.org/D13133

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MFH

Sponsored by: The FreeBSD Foundation

Use __FBSDID() for .c files from lib/libthr/thread.

Sponsored by: The FreeBSD Foundation

MFC @ r241285

IFC @ r242684

Sync from head

Merge head r233826 through r239010.

Don't assign same value.

Eliminate duplicated code.

Don't forget to release a thread reference count,
replace _thr_ref_add() with _thr_find_thread(),
so reference count is no longer needed.

MFC after: 3 days

use rtprio_thread system call to get or set thread priority.

Pass correct parameter size.

Caching scheduling policy and priority in userland, a critical but baddly
written application is frequently changing thread priority for SCHED_OTHER
policy.

Use thr_setscheduler, thr_getscheduler and thr_setschedparam to implement
pthread functions.

Use kernel facilities to support real-time scheduling.

- Use same priority range returned by kernel's sched_get_priority_min()
and sched_get_priority_max() syscalls.
- Remove unused fields from structure pthread_attr.

WARNS level 4 cleanup.

Remove priority mutex code because it does not work correctly,
to make it work, turnstile like mechanism to support priority
propagating and other realtime scheduling options in kernel
should be avai

Remove priority mutex code because it does not work correctly,
to make it work, turnstile like mechanism to support priority
propagating and other realtime scheduling options in kernel
should be available to userland mutex, for the moment, I just
want to make libthr be simple and efficient thread library.

Discussed with: deischen, julian

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Import my recent 1:1 threading working. some features improved includes:
1. fast simple type mutex.
2. __thread tls works.
3. asynchronous cancellation works ( using signal ).
4. thread synchroni

Import my recent 1:1 threading working. some features improved includes:
1. fast simple type mutex.
2. __thread tls works.
3. asynchronous cancellation works ( using signal ).
4. thread synchronization is fully based on umtx, mainly, condition
variable and other synchronization objects were rewritten by using
umtx directly. those objects can be shared between processes via
shared memory, it has to change ABI which does not happen yet.
5. default stack size is increased to 1M on 32 bits platform, 2M for
64 bits platform.
As the result, some mysql super-smack benchmarks show performance is
improved massivly.

Okayed by: jeff, mtm, rwatson, scottl

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o Assertions to catch that stuff that shouldn't happen is not happening.
o In the rwlock code: move a duplicated check inside an if..else to after
the if...else clause.
o When initializing a static

o Assertions to catch that stuff that shouldn't happen is not happening.
o In the rwlock code: move a duplicated check inside an if..else to after
the if...else clause.
o When initializing a static rwlock move the initialization check
inside the lock.
o In thr_setschedparam.c: When breaking out of the trylock...retry if busy
loop make sure to reset the mtx pointer to null if the mutex is nolonger
in a queue.

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Make libthr async-signal-safe without costly signal masking. The guidlines I
followed are: Only 3 functions (pthread_cancel, pthread_setcancelstate,
pthread_setcanceltype) are required to be async-si

Make libthr async-signal-safe without costly signal masking. The guidlines I
followed are: Only 3 functions (pthread_cancel, pthread_setcancelstate,
pthread_setcanceltype) are required to be async-signal-safe by POSIX. None of
the rest of the pthread api is required to be async-signal-safe. This means
that only the three mentioned functions are safe to use from inside
signal handlers.
However, there are certain system/libc calls that are
cancellation points that a caller may call from within a signal handler,
and since they are cancellation points calls have to be made into libthr
to test for cancellation and exit the thread if necessary. So, the
cancellation test and thread exit code paths must be async-signal-safe
as well. A summary of the changes follows:

o Almost all of the code paths that masked signals, as well as locking the
pthread structure now lock only the pthread structure.
o Signals are masked (and left that way) as soon as a thread enters
pthread_exit().
o The active and dead threads locks now explicitly require that signals
are masked.
o Access to the isdead field of the pthread structure is protected by both
the active and dead list locks for writing. Either one is sufficient for
reading.
o The thread state and type fields have been combined into one three-state
switch to make it easier to read without requiring a lock. It doesn't need
a lock for writing (and therefore for reading either) because only the
current thread can write to it and it is an integer value.
o The thread state field of the pthread structure has been eliminated. It
was an unnecessary field that mostly duplicated the flags field, but
required additional locking that would make a lot more code paths require
signal masking. Any truly unique values (such as PS_DEAD) have been
reborn as separate members of the pthread structure.
o Since the mutex and condvar pthread functions are not async-signal-safe
there is no need to muck about with the wait queues when handling
a signal ...
o ... which also removes the need for wrapping signal handlers and sigaction(2).
o The condvar and mutex async-cancellation code had to be revised as a result
of some of these changes, which resulted in semi-unrelated changes which
would have been difficult to work on as a separate commit, so they are
included as well.

The only part of the changes I am worried about is related to locking for
the pthread joining fields. But, I will take a closer look at them once this
mega-patch is committed.

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o Catch up with the mutex priority protocol fixes.
o Move pthread_getschedparam() into the same file with it's
pthread_set* counterpart. Copyright on both files is identical.