When _PTHREADSINVARIANTS is defined SIGABRT is not included
in the set of signals to block.
Also, make the PANIC macro call abort() instead of simply
exiting.

Change all instances of THR_LOCK/UNLOCK, etc to UMTX_*.
It is a more acurate description of the locks they
operate on.

Sweep through pthread locking and use the new locking primitives for
libthr.

In a critical section, separate the aquisition of the thread lock
and the disabling of signals. What we are really interested in is
keeping track of recursive disabling of signals. We should not
be r

In a critical section, separate the aquisition of the thread lock
and the disabling of signals. What we are really interested in is
keeping track of recursive disabling of signals. We should not
be recursively acquiring thread locks. Any such situations should
be reorganized to not require a recursive lock.

Separating the two out also allows us to block signals independent of
acquiring thread locks. This will be needed in libthr in the near future when
we put the pieces together to protect libc functions that use pthread mutexes
and low level locks.

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Make _thread_suspend work with both the old broken sigtimedwait
implementation and the new improved one. We now precompute the
signal set passed to sigtimedwait, using an inverted set when
necessary

Make _thread_suspend work with both the old broken sigtimedwait
implementation and the new improved one. We now precompute the
signal set passed to sigtimedwait, using an inverted set when
necessary for compatibility with older kernels.

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The libthr code makes use of higher-level primitives (pthread_mutex_t and
pthread_cond_t) internaly in addition to the low-level spinlock_t. The
garbage collector mutex and condition variable are two

The libthr code makes use of higher-level primitives (pthread_mutex_t and
pthread_cond_t) internaly in addition to the low-level spinlock_t. The
garbage collector mutex and condition variable are two such examples. This
might lead to critical sections nested within critical sections. Implement
a reference counting mechanism so that signals are masked only on the first
entry and unmasked on the last exit.

I'm not sure I like the idea of nested critical sections, but if
the library is going to use the pthread primitives it might be necessary.

Approved by: re/blanket libthr

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EDOOFUS
Prevent one thread from messing up another thread's saved signal
mask by saving it in struct pthread instead of leaving it as a
global variable. D'oh!

Approved by: re/blanket libthr

Make WARNS2 clean. The fixes mostly included:
o removed unused variables
o explicit inclusion of header files
o prototypes for externally defined functions

Approved by: re/blanket libthr

msg1

Use STDERR_FILENO as the file descriptor passed to _thread_printf()
instead of 0 (ie stdin). Writing to stdin may not be possible.

- Don't drop and reacquire giant in thread_suspend(). Change callers to do
this manually. This will facilitate the unrolling of giant.
- Don't allow giant to recurse anymore. This should never

- Don't drop and reacquire giant in thread_suspend(). Change callers to do
this manually. This will facilitate the unrolling of giant.
- Don't allow giant to recurse anymore. This should never happen.

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- Add libthr but don't hook it up to the regular build yet. This is an
adaptation of libc_r for the thr system call interface. This is beta
quality code.