'RELENG_6_0_0_RELEASE'.

This commit was manufactured to restore the state of the 6.0-RELEASE image.

signals instead of having more intricate knowledge of thread state
within signal handling.

Simplify signal code because of above (by David Xu).

Use macros for libpthread usage of pthread_cleanup_push() and
pthread_cleanup_pop().  This removes some instances of malloc()
and free() from the semaphore and pthread_once() implementations.

When single threaded and forking(), make sure that the current
thread's signal mask is inherited by the forked thread.

Use private mutexes for libc and libpthread.  Signals are
deferred while threads hold private mutexes.  This fix also
breaks www/linuxpluginwrapper; a patch that fixes it is at
http://people.freebsd.org/~deischen/kse/linuxpluginwrapper.diff

Fix race condition in condition variables where handling a
signal (pthread_kill() or kill()) may not see a wakeup
(pthread_cond_signal() or pthread_cond_broadcast()).

In collaboration with:	davidxu

avoids signal to be blocked when otherwise it can be handled.

locks for [libc] spinlock implementation.  This was previously backed
out because it exposed a bug in ia64 implementation.

OK'd by:	marcel

locks until we know why this breaks ia64.

Reported by:	marcel

Reviewed by: deischen

internal lock, not a pthread spinlock).

Reviewed by:	davidxu

low-level lock used by the libpthread implementation.  In the
future, we'll eliminate spinlocks from libc but that will wait
until after 5.1-release.

Don't call an application signal handler if the handler is
the same as the library-installed handler.  This seems to
be possible after a fork and is the cause of konsole hangs.

Approved by:	re@ (jhb)

  KSEs when it's thread exits; allow the GC handler to do that.

o Make spinlock/spinlock critical regions.

The following were submitted by davidxu

  o Alow thr_switch() to take a null mailbox argument.

  o Better protect cancellation checks.

  o Don't set KSE specific data when creating new KSEs; rely on the
    first upcall of the KSE to set it.

  o Add the ability to set the maximum concurrency level and do this
    automatically.  We should have a way to enable/disable this with
    some sort of tunable because some applications may not want this
    to be the default.

  o Hold the scheduling lock across thread switch calls.

  o If scheduling of a thread fails, make sure to remove it from the list
    of active threads.

  o Better protect accesses to a joining threads when the target thread is
    exited and detached.

  o Remove some macro definitions that are now provided by <sys/kse.h>.

  o Don't leave the library in threaded mode if creation of the initial
    KSE fails.

  o Wakeup idle KSEs when there are threads ready to run.

  o Maintain the number of threads active in the priority queue.

environment.  This includes support for multiple KSEs and KSEGs.

The ability to create more than 1 KSE via pthread_setconcurrency()
is in the works as well as support for PTHREAD_SCOPE_SYSTEM threads.
Those should come shortly.

There are still some known issues which davidxu and I are working
on, but it'll make it easier for us by committing what we have.

This library now passes all of the ACE tests that libc_r passes
with the exception of one.  It also seems to work OK with KDE
including konqueror, kwrite, etc.  I haven't been able to get
mozilla to run due to lack of java plugin, so I'd be interested
to see how it works with that.

Reviewed by:	davidxu