- If our user_pri doesn't match our actual priority our priority has been

   elevated either due to priority propagation or because we're in the
   kernel in either case, put us on the current queue so that we dont
   stop others from using important resources.  At some point the priority
   elevations from sleeping in the kernel should go away.
 - Remove an optimization in sched_userret().  Before we would only set
   NEEDRESCHED if there was something of a higher priority available.  This
   is a trivial optimization and it breaks priority propagation because it
   doesn't take threads which we may be blocking into account.  Notice that
   the thread which is blocking others gets up to one tick of cpu time before
   we honor this NEEDRESCHED in sched_clock().

1 files changed, 10 insertions, 3 deletions

diff --git a/sys/kern/sched_ule.c b/sys/kern/sched_ule.c
index 635a0dd..c0e2044 100644
--- a/sys/kern/sched_ule.c
+++ b/sys/kern/sched_ule.c
@@ -182,9 +182,8 @@ struct td_sched *thread0_sched = &td_sched;
 #define	SCHED_INTERACTIVE(kg)						\
     (sched_interact_score(kg) < SCHED_INTERACT_THRESH)
 #define	SCHED_CURR(kg, ke)						\
-    (ke->ke_thread->td_priority < PRI_MIN_TIMESHARE ||			\
-    SCHED_INTERACTIVE(kg) ||						\
-    mtx_ownedby(&Giant, (ke)->ke_thread))
+    (ke->ke_thread->td_priority != kg->kg_user_pri ||			\
+    SCHED_INTERACTIVE(kg))
 
 /*
  * Cpu percentage computation macros and defines.
@@ -1152,14 +1151,21 @@ void
 sched_userret(struct thread *td)
 {
 	struct ksegrp *kg;
+#if 0
 	struct kseq *kseq;
 	struct kse *ke;
+#endif
 	
 	kg = td->td_ksegrp;
 
 	if (td->td_priority != kg->kg_user_pri) {
 		mtx_lock_spin(&sched_lock);
 		td->td_priority = kg->kg_user_pri;
+		/*
+		 * This optimization is temporarily disabled because it
+		 * breaks priority propagation.
+		 */
+#if 0
 		kseq = KSEQ_SELF();
 		if (td->td_ksegrp->kg_pri_class == PRI_TIMESHARE &&
 #ifdef SMP
@@ -1169,6 +1175,7 @@ sched_userret(struct thread *td)
 #endif
 		    (ke = kseq_choose(kseq, 0)) != NULL &&
 		    ke->ke_thread->td_priority < td->td_priority)
+#endif
 			curthread->td_flags |= TDF_NEEDRESCHED;
 		mtx_unlock_spin(&sched_lock);
 	}