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

Add _pthread_mutex_init_calloc_cb() to libthr and libkse, so that malloc(3)
(part of libc) can use pthreads mutexes without causing infinite recursion
during initialization.

Convert ceiling type to unsigned integer before comparing, fix compiler
warnings.

Avoid doing adaptive spinning for priority protected mutex, current
implementation always does lock in kernel.

Don't do adaptive spinning if it is running on UP kernel.

Restore revision 1.55, the kris's adaptive mutex type.

Adaptive mutexes should have the same deadlock detection properties that
default (errorcheck) mutexes do.

Noticed by: davidxu

Add my recent work of adaptive spin mutex code. Use two environments variable
to tune pthread mutex performance:
1. LIBPTHREAD_SPINLOOPS
If a pthread mutex is being locked by another thread, this en

Add my recent work of adaptive spin mutex code. Use two environments variable
to tune pthread mutex performance:
1. LIBPTHREAD_SPINLOOPS
If a pthread mutex is being locked by another thread, this environment
variable sets total number of spin loops before the current thread
sleeps in kernel, this saves a syscall overhead if the mutex will be
unlocked very soon (well written application code).
2. LIBPTHREAD_YIELDLOOPS
If a pthread mutex is being locked by other threads, this environment
variable sets total number of sched_yield() loops before the currrent
thread sleeps in kernel. if a pthread mutex is locked, the current thread
gives up cpu, but will not sleep in kernel, this means, current thread
does not set contention bit in mutex, but let lock owner to run again
if the owner is on kernel's run queue, and when lock owner unlocks the
mutex, it does not need to enter kernel and do lots of work to resume
mutex waiters, in some cases, this saves lots of syscall overheads for
mutex owner.

In my practice, sometimes LIBPTHREAD_YIELDLOOPS can massively improve performance
than LIBPTHREAD_SPINLOOPS, this depends on application. These two environments
are global to all pthread mutex, there is no interface to set them for each
pthread mutex, the default values are zero, this means spinning is turned off
by default.

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Add a new "non-portable" mutex type, PTHREAD_MUTEX_ADAPTIVE_NP. This
is also implemented in glibc and is used by a number of existing
applications (mysql, firefox, etc).

This mutex type is a defaul

Add a new "non-portable" mutex type, PTHREAD_MUTEX_ADAPTIVE_NP. This
is also implemented in glibc and is used by a number of existing
applications (mysql, firefox, etc).

This mutex type is a default mutex with the additional property that
it spins briefly when attempting to acquire a contested lock, doing
trylock operations in userland before entering the kernel to block if
eventually unsuccessful.

The expectation is that applications requesting this mutex type know
that the mutex is likely to be only held for very brief periods, so it
is faster to spin in userland and probably succeed in acquiring the
mutex, than to enter the kernel and sleep, only to be woken up almost
immediately. This can help significantly in certain cases when
pthread mutexes are heavily contended and held for brief durations
(such as mysql).

Spin up to 200 times before entering the kernel, which represents only
a few us on modern CPUs. No performance degradation was observed with
this value and it is sufficient to avoid a large performance drop in
mysql performance in the heavily contended pthread mutex case.

The libkse implementation is a NOP.

Reviewed by: jeff
MFC after: 3 days

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backout experimental adaptive spinning mutex for product use.

Insert mutex at tail if it has highest ceiling.

Oops, don't corrupt the list.

Check if the PP mutex is recursive, if we have already locked it, place the
mutex in right order sorted by priority ceiling.

Check environment variable PTHREAD_ADAPTIVE_SPIN, if it is set, use
it as a default spin cycle count.

Create inline function _thr_umutex_trylock2 to only try one atomic
operation, if it is failed, we call syscall directly, this saves
one atomic operation per lock contention.

Move code calculating new inherited priority into single function.

Use return value of _thr_umutex_lock instead of using zero.

Use umutex APIs to implement pthread_mutex, member pp_mutexq is added
into pthread structure to keep track of locked PTHREAD_PRIO_PROTECT mutex,
no real mutex code is changed, the mutex locking and u

Use umutex APIs to implement pthread_mutex, member pp_mutexq is added
into pthread structure to keep track of locked PTHREAD_PRIO_PROTECT mutex,
no real mutex code is changed, the mutex locking and unlocking code should
has same performance as before.

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Axe unused member field.

Unexpand two TAILQ_FOREACH_SAFE cases.

Ok'ed by: davidxu

Remove unused member field m_queue.

Do not check validity of timeout if a mutex can be acquired immediately.
Completly drop recursive mutex in pthread_cond_wait and restore recursive
after resumption. Reorganize code to make gcc to gen

Do not check validity of timeout if a mutex can be acquired immediately.
Completly drop recursive mutex in pthread_cond_wait and restore recursive
after resumption. Reorganize code to make gcc to generate better code.

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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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Reimplement mutex_init to get rid of compile warning.