o Set TP using inline assembly to avoid dead code elimination.
o Eliminate _tcb.
Merge from r161840:
Stylize: avoid using a global register variable.
Merge from r157461:
Simplify _get_curthread() and _tcb_ctor because libc and rtld now
already allocate thread pointer space in tls block for initial thread.
Merge from r177853:
Replace function _umtx_op with _umtx_op_err, the later function directly
returns errno, because errno can be mucked by user's signal handler and
most of pthread api heavily depends on errno to be correct, this change
should improve stability of the thread library.
MFC after: 1 week
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
