From 27ee18ad336ae50bc29692275768befa0ee9b564 Mon Sep 17 00:00:00 2001
From: Ryan Stone <rstone@FreeBSD.org>
Date: Thu, 16 Feb 2017 21:18:31 +0000
Subject: [PATCH] Revert r313814 and r313816

Something evidently got mangled in my git tree in between testing and
review, as an old and broken version of the patch was apparently submitted
to svn.  Revert this while I work out what went wrong.

Reported by:	tuexen
Pointy hat to:	rstone
---
 sys/kern/sched_4bsd.c | 40 +---------------------------------------
 sys/kern/sched_ule.c  | 31 +++++++------------------------
 2 files changed, 8 insertions(+), 63 deletions(-)

diff --git a/sys/kern/sched_4bsd.c b/sys/kern/sched_4bsd.c
index a42c1534f89e..534f59cd5a42 100644
--- a/sys/kern/sched_4bsd.c
+++ b/sys/kern/sched_4bsd.c
@@ -816,12 +816,7 @@ sched_class(struct thread *td, int class)
 static void
 sched_priority(struct thread *td, u_char prio)
 {
-	struct thread *newtd;
-	struct runq *rq;
-	u_char orig_pri;
-#ifdef SMP
-	struct thread *cputd;
-#endif
+
 
 	KTR_POINT3(KTR_SCHED, "thread", sched_tdname(td), "priority change",
 	    "prio:%d", td->td_priority, "new prio:%d", prio, KTR_ATTR_LINKED,
@@ -837,43 +832,10 @@ sched_priority(struct thread *td, u_char prio)
 	THREAD_LOCK_ASSERT(td, MA_OWNED);
 	if (td->td_priority == prio)
 		return;
-	orig_pri = td->td_priority;
 	td->td_priority = prio;
 	if (TD_ON_RUNQ(td) && td->td_rqindex != (prio / RQ_PPQ)) {
 		sched_rem(td);
 		sched_add(td, SRQ_BORING);
-	} else if (orig_pri < prio && TD_IS_RUNNING(td)) {
-		/*
-		 * If we have decreased the priority of a running thread, we
-		 * have to check if it should be preempted.
-		 */
-		rq = &runq;
-		newtd = runq_choose(&runq);
-#ifdef SMP
-		cputd = runq_choose(&runq_pcpu[td->td_oncpu]);
-		if (newtd == NULL ||
-		    (cputd != NULL && cputd->td_priority < td->td_priority))
-			newtd = cputd;
-#endif
-
-		if (newtd != NULL && newtd->td_priority < prio
-#ifndef FULL_PREEMPTION
-		    && (newtd->td_priority <= PRI_MAX_ITHD ||
-		        prio >= PRI_MIN_IDLE))
-#endif
-		) {
-			if (td == curthread)
-				/*
-				 * Don't reschedule the thread here as it may
-				 * be losing priority because it has released a
-				 * mutex, and in that case we need it to finish
-				 * releasing the lock before it gets preempted.
-				 */
-				td->td_owepreempt = 1;
-			else
-				kick_other_cpu(newtd->td_priority,
-				    td->td_oncpu);
-		}
 	}
 }
 
diff --git a/sys/kern/sched_ule.c b/sys/kern/sched_ule.c
index 93644469ce53..b650f24db9e5 100644
--- a/sys/kern/sched_ule.c
+++ b/sys/kern/sched_ule.c
@@ -319,7 +319,7 @@ static void tdq_add(struct tdq *, struct thread *, int);
 #ifdef SMP
 static int tdq_move(struct tdq *, struct tdq *);
 static int tdq_idled(struct tdq *);
-static void tdq_notify(struct tdq *, int);
+static void tdq_notify(struct tdq *, struct thread *);
 static struct thread *tdq_steal(struct tdq *, int);
 static struct thread *runq_steal(struct runq *, int);
 static int sched_pickcpu(struct thread *, int);
@@ -1040,14 +1040,16 @@ tdq_idled(struct tdq *tdq)
  * Notify a remote cpu of new work.  Sends an IPI if criteria are met.
  */
 static void
-tdq_notify(struct tdq *tdq, int pri)
+tdq_notify(struct tdq *tdq, struct thread *td)
 {
 	struct thread *ctd;
+	int pri;
 	int cpu;
 
 	if (tdq->tdq_ipipending)
 		return;
-	cpu = TDQ_ID(tdq);
+	cpu = td_get_sched(td)->ts_cpu;
+	pri = td->td_priority;
 	ctd = pcpu_find(cpu)->pc_curthread;
 	if (!sched_shouldpreempt(pri, ctd->td_priority, 1))
 		return;
@@ -1673,22 +1675,6 @@ sched_pctcpu_update(struct td_sched *ts, int run)
 	ts->ts_ltick = t;
 }
 
-static void
-sched_check_preempt(struct tdq *tdq, struct thread *td)
-{
-
-	KASSERT(TD_IS_RUNNING(td), ("thread is not running"));
-	TDQ_LOCK_ASSERT(tdq, MA_OWNED);
-	KASSERT(tdq == TDQ_CPU(td->td_sched->ts_cpu),
-	    ("tdq does not contain td"));
-
-	if (tdq == TDQ_SELF()) {
-		if (sched_shouldpreempt(tdq->tdq_lowpri, td->td_priority, 0))
-			td->td_owepreempt = 1;
-	} else
-		tdq_notify(tdq, tdq->tdq_lowpri);
-}
-
 /*
  * Adjust the priority of a thread.  Move it to the appropriate run-queue
  * if necessary.  This is the back-end for several priority related
@@ -1740,9 +1726,6 @@ sched_thread_priority(struct thread *td, u_char prio)
 			tdq->tdq_lowpri = prio;
 		else if (tdq->tdq_lowpri == oldpri)
 			tdq_setlowpri(tdq, td);
-
-		if (oldpri < prio)
-			sched_check_preempt(tdq, td);
 		return;
 	}
 	td->td_priority = prio;
@@ -1871,7 +1854,7 @@ sched_switch_migrate(struct tdq *tdq, struct thread *td, int flags)
 	 */
 	tdq_lock_pair(tdn, tdq);
 	tdq_add(tdn, td, flags);
-	tdq_notify(tdn, td->td_priority);
+	tdq_notify(tdn, td);
 	TDQ_UNLOCK(tdn);
 	spinlock_exit();
 #endif
@@ -2446,7 +2429,7 @@ sched_add(struct thread *td, int flags)
 	tdq = sched_setcpu(td, cpu, flags);
 	tdq_add(tdq, td, flags);
 	if (cpu != PCPU_GET(cpuid)) {
-		tdq_notify(tdq, td->td_priority);
+		tdq_notify(tdq, td);
 		return;
 	}
 #else