Add a method of yielding the current thread with the scheduler

lock held (_thr_sched_switch_unlocked()) and use this to avoid
dropping the scheduler lock and having the scheduler retake the
same lock again.

Add a better way of detecting if a low-level lock is in use.

When switching out a thread due to blocking in the UTS, don't
switch to the KSE's scheduler stack only to switch back to
another thread.  If possible switch to the new thread directly
from the old thread and avoid the overhead of the extra
context switch.

Check for pending signals on a thread when entering the scheduler
and add them to the threads signal frame.  This includes some
other minor signal fixes.

Most of this was a joint effor between davidxu and myself.

Reviewed by:	davidxu
Approved by:	re@ (blanket for libpthread)

1 files changed, 2 insertions, 0 deletions

diff --git a/lib/libkse/thread/thr_init.c b/lib/libkse/thread/thr_init.c
index f06df6c..5bfb3c7 100644
--- a/lib/libkse/thread/thr_init.c
+++ b/lib/libkse/thread/thr_init.c
@@ -72,6 +72,7 @@
 int	__pthread_cond_wait(pthread_cond_t *, pthread_mutex_t *);
 int	__pthread_mutex_lock(pthread_mutex_t *);
 int	__pthread_mutex_trylock(pthread_mutex_t *);
+void	_thread_init_hack(void);
 
 static void init_private(void);
 static void init_main_thread(struct pthread *thread);
@@ -131,6 +132,7 @@ static void *references[] = {
 	&_sigsuspend,
 	&_socket,
 	&_socketpair,
+	&_thread_init_hack,
 	&_wait4,
 	&_write,
 	&_writev