IFC @ r238370

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

Merge head r233826 through r236168.

Return EBUSY for PTHREAD_MUTEX_ADAPTIVE_NP too when the mutex could not
be acquired.

PR: 168317
MFC after: 3 days

Return 0 instead of garbage value.

Found by: clang static analyzer

Always clear flag PMUTEX_FLAG_DEFERED when unlocking, as it is only
significant for lock owner.

MFp4:

- Add flags CVWAIT_ABSTIME and CVWAIT_CLOCKID for umtx kernel based
condition variable, this should eliminate an extra system call to get
current time.

- Add sub-function UMTX_OP_NWAKE_PR

MFp4:

- Add flags CVWAIT_ABSTIME and CVWAIT_CLOCKID for umtx kernel based
condition variable, this should eliminate an extra system call to get
current time.

- Add sub-function UMTX_OP_NWAKE_PRIVATE to wake up N channels in single
system call. Create userland sleep queue for condition variable, in most
cases, thread will wait in the queue, the pthread_cond_signal will defer
thread wakeup until the mutex is unlocked, it tries to avoid an extra
system call and a extra context switch in time window of pthread_cond_signal
and pthread_mutex_unlock.

The changes are part of process-shared mutex project.

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Sync: merge r214353 through r214648 from ^/head.

Remove locking and unlock in pthread_mutex_destroy, because
it can not fix race condition in application code, as a result,
the problem described in PR threads/151767 is avoided.

Check invalid mutex in _mutex_cv_unlock.

In current code, statically initialized and destroyed object have
same null value, the code can not distinguish between them, to
fix the problem, now a destroyed object is assigned to a non-null
valu

In current code, statically initialized and destroyed object have
same null value, the code can not distinguish between them, to
fix the problem, now a destroyed object is assigned to a non-null
value, and it will be rejected by some pthread functions.
PTHREAD_ADAPTIVE_MUTEX_INITIALIZER_NP is changed to number 1, so that
adaptive mutex can be statically initialized correctly.

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Change atfork lock from mutex to rwlock, also make mutexes used by malloc()
module private type, when private type mutex is locked/unlocked, thread
critical region is entered or leaved. These changes

Change atfork lock from mutex to rwlock, also make mutexes used by malloc()
module private type, when private type mutex is locked/unlocked, thread
critical region is entered or leaved. These changes makes fork()
async-signal safe which required by POSIX. Note that user's atfork handler
still needs to be async-signal safe, but it is not problem of libthr, it
is user's responsiblity.

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Add two commands to _umtx_op system call to allow a simple mutex to be
locked and unlocked completely in userland. by locking and unlocking mutex
in userland, it reduces the total time a mutex is loc

Add two commands to _umtx_op system call to allow a simple mutex to be
locked and unlocked completely in userland. by locking and unlocking mutex
in userland, it reduces the total time a mutex is locked by a thread,
in some application code, a mutex only protects a small piece of code, the
code's execution time is less than a simple system call, if a lock contention
happens, however in current implemenation, the lock holder has to extend its
locking time and enter kernel to unlock it, the change avoids this disadvantage,
it first sets mutex to free state and then enters kernel and wake one waiter
up. This improves performance dramatically in some sysbench mutex tests.

Tested by: kris
Sounds great: jeff

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- Reduce function call overhead for uncontended case.
- Remove unused flags MUTEX_FLAGS_* and their code.
- Check validity of the timeout parameter in mutex_self_lock().

Increase the default MUTEX_ADAPTIVE_SPINS to 2000, after further
testing it turns out 200 was too short to give good adaptive
performance.

Reviewed by: jeff
MFC after: 1 week

Fixed mis-implementation of pthread_mutex_get{spin,yield}loops_np().

Reviewed by: davidxu

_pthread_mutex_isowned_np(): use a more reliable method; the current code
will work in simple cases, but may fail in more complicated ones.

Reviewed by: davidxu

Remove unnecessary prototype.

Per discussion on -threads, rename _islocked_np() to _isowned_np().

After careful consideration (and a brief discussion with attilio@), change
the semantics of pthread_mutex_islocked_np() to return true if and only if
the mutex is held by the current thread.

Obvious

After careful consideration (and a brief discussion with attilio@), change
the semantics of pthread_mutex_islocked_np() to return true if and only if
the mutex is held by the current thread.

Obviously, change the regression test to match.

MFC after: 2 weeks

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Add pthread_mutex_islocked_np(), a cheap way to verify that a mutex is
locked. This is intended primarily to support the userland equivalent
of the various *_ASSERT_LOCKED() macros we have in the ke

Add pthread_mutex_islocked_np(), a cheap way to verify that a mutex is
locked. This is intended primarily to support the userland equivalent
of the various *_ASSERT_LOCKED() macros we have in the kernel.

MFC after: 2 weeks

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Add function prototypes.

1. Add function pthread_mutex_setspinloops_np to turn a mutex's spin
loop count.
2. Add function pthread_mutex_setyieldloops_np to turn a mutex's yield
loop count.
3. Make environment variables

1. Add function pthread_mutex_setspinloops_np to turn a mutex's spin
loop count.
2. Add function pthread_mutex_setyieldloops_np to turn a mutex's yield
loop count.
3. Make environment variables PTHREAD_SPINLOOPS and PTHREAD_YIELDLOOPS
to be only used for turnning PTHREAD_MUTEX_ADAPTIVE_NP mutex.

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Enclose all code for macro ENQUEUE_MUTEX in do while statement, and
add missing brackets.

MFC: after 1 day

Fix pointer dereferencing problems in _pthread_mutex_init_calloc_cb() that
were obscured by pseudo-opaque pthreads API pointer casting.