Add a preemption point when a mutex or condition variable is

handed-off/signaled to a higher priority thread.  Note that when
there are idle KSEs that could run the higher priority thread,
we still add the preemption point because it seems to take the
kernel a while to schedule an idle KSE.  The drawbacks are that
threads will be swapped more often between CPUs (KSEs) and
that there will be an extra userland context switch (the idle
KSE is still woken and will probably resume the preempted
thread).  We'll revisit this if and when idle CPU/KSE wakeup
times improve.

Inspired by:	Petri Helenius <pete@he.iki.fi>
Reviewed by:	davidxu

1 files changed, 8 insertions, 0 deletions

diff --git a/lib/libpthread/thread/thr_cond.c b/lib/libpthread/thread/thr_cond.c
index 9e73c61..9703da6 100644
--- a/lib/libpthread/thread/thr_cond.c
+++ b/lib/libpthread/thread/thr_cond.c
@@ -615,6 +615,10 @@ _pthread_cond_signal(pthread_cond_t * cond)
 			    != NULL) {
 				THR_SCHED_LOCK(curthread, pthread);
 				cond_queue_remove(*cond, pthread);
+				if ((pthread->kseg == curthread->kseg) &&
+				    (pthread->active_priority >
+				    curthread->active_priority))
+					curthread->critical_yield = 1;
 				_thr_setrunnable_unlocked(pthread);
 				THR_SCHED_UNLOCK(curthread, pthread);
 			}
@@ -674,6 +678,10 @@ _pthread_cond_broadcast(pthread_cond_t * cond)
 			    != NULL) {
 				THR_SCHED_LOCK(curthread, pthread);
 				cond_queue_remove(*cond, pthread);
+				if ((pthread->kseg == curthread->kseg) &&
+				    (pthread->active_priority >
+				    curthread->active_priority))
+					curthread->critical_yield = 1;
 				_thr_setrunnable_unlocked(pthread);
 				THR_SCHED_UNLOCK(curthread, pthread);
 			}