Tidy up the scheduler's code for changing the priority of a thread.

Logically pretty much a NOP.

sys/kern/kern_switch.c

@@ -277,13 +277,14 @@ kse_reassign(struct kse *ke)
 	CTR1(KTR_RUNQ, "kse_reassign: ke%p idled", ke);
 }
 
+#if 0
 /*
  * Remove a thread from its KSEGRP's run queue.
  * This in turn may remove it from a KSE if it was already assigned
  * to one, possibly causing a new thread to be assigned to the KSE
  * and the KSE getting a new priority (unless it's a BOUND thread/KSE pair).
  */
-void
+static void
 remrunqueue(struct thread *td)
 {
 	struct thread *td2, *td3;
@@ -325,6 +326,51 @@ remrunqueue(struct thread *td)
 		kse_reassign(ke);
 	}
 }
+#endif
+
+/*
+ * Change the priority of a thread that is on the run queue.
+ */
+void
+adjustrunqueue( struct thread *td, int newpri) 
+{
+	struct ksegrp *kg;
+	struct kse *ke;
+
+	mtx_assert(&sched_lock, MA_OWNED);
+	KASSERT ((TD_ON_RUNQ(td)), ("adjustrunqueue: Bad state on run queue"));
+	/*
+	 * If it's a bound thread/KSE pair, take the shortcut. All non-KSE
+	 * threads are BOUND.
+	 */
+	ke = td->td_kse;
+	CTR1(KTR_RUNQ, "adjustrunqueue: td%p", td);
+	if ((td->td_flags & TDF_UNBOUND) == 0)  {
+		/* We only care about the kse in the run queue. */
+		if (ke->ke_rqindex != (newpri / RQ_PPQ)) {
+			sched_rem(ke);
+			td->td_priority = newpri;
+			sched_add(ke);
+		}
+		return;
+	}
+	/*
+	 * An unbound thread. This is not optimised yet.
+	 */
+	kg = td->td_ksegrp;
+	kg->kg_runnable--;
+	TD_SET_CAN_RUN(td);
+	if (ke) {
+		if (kg->kg_last_assigned == td) {
+			kg->kg_last_assigned =
+			    TAILQ_PREV(td, threadqueue, td_runq);
+		}
+		sched_rem(ke);
+	}
+	TAILQ_REMOVE(&kg->kg_runq, td, td_runq);
+	td->td_priority = newpri;
+	setrunqueue(td);
+}
 
 void
 setrunqueue(struct thread *td)
@@ -662,18 +708,6 @@ runq_remove(struct runq *rq, struct kse *ke)
 	}
 }
 
-#if 0
-static void 
-runq_readjust(struct runq *rq, struct kse *ke)
-{
-
-	if (ke->ke_rqindex != (ke->ke_thread->td_priority / RQ_PPQ)) {
-		runq_remove(rq, ke);
-		runq_add(rq, ke);
-	}
-}
-#endif
-
 #if 0
 void
 panc(char *string1, char *string2)

sys/kern/ksched.c

@@ -187,10 +187,7 @@ int ksched_setscheduler(register_t *ret, struct ksched *ksched,
 					td->td_kse->ke_flags |= KEF_NEEDRESCHED;
 				} else if (TD_ON_RUNQ(td)) {
 					if (td->td_priority > kg->kg_user_pri) {
-						remrunqueue(td);
-						td->td_priority =
-						    kg->kg_user_pri;
-						setrunqueue(td);
+						sched_prio(td, kg->kg_user_pri);
 					}
 				}
 			}
@@ -220,10 +217,7 @@ int ksched_setscheduler(register_t *ret, struct ksched *ksched,
 					td->td_kse->ke_flags |= KEF_NEEDRESCHED;
 				} else if (TD_ON_RUNQ(td)) {
 					if (td->td_priority > kg->kg_user_pri) {
-						remrunqueue(td);
-						td->td_priority =
-						    kg->kg_user_pri;
-						setrunqueue(td);
+						sched_prio(td, kg->kg_user_pri);
 					}
 				}
 				

sys/kern/sched_4bsd.c

@@ -316,30 +316,8 @@ schedcpu(void *arg)
 			kg->kg_estcpu = decay_cpu(loadfac, kg->kg_estcpu);
 		      	resetpriority(kg);
 			FOREACH_THREAD_IN_GROUP(kg, td) {
-				int changedqueue;
 				if (td->td_priority >= PUSER) {
-					/*
-					 * Only change the priority
-					 * of threads that are still at their
-					 * user priority. 
-					 * XXXKSE This is problematic
-					 * as we may need to re-order
-					 * the threads on the KSEG list.
-					 */
-					changedqueue =
-					    ((td->td_priority / RQ_PPQ) !=
-					     (kg->kg_user_pri / RQ_PPQ));
-
-					td->td_priority = kg->kg_user_pri;
-					if (changedqueue && TD_ON_RUNQ(td)) {
-						/* this could be optimised */
-						remrunqueue(td);
-						td->td_priority =
-						    kg->kg_user_pri;
-						setrunqueue(td);
-					} else {
-						td->td_priority = kg->kg_user_pri;
-					}
+					sched_prio(td, kg->kg_user_pri);
 				}
 			}
 		} /* end of ksegrp loop */
@@ -491,14 +469,20 @@ sched_nice(struct ksegrp *kg, int nice)
 	resetpriority(kg);
 }
 
+/*
+ * Adjust the priority of a thread.
+ * This may include moving the thread within the KSEGRP,
+ * changing the assignment of a kse to the thread,
+ * and moving a KSE in the system run queue.
+ */
 void
 sched_prio(struct thread *td, u_char prio)
 {
-	td->td_priority = prio;
 
 	if (TD_ON_RUNQ(td)) {
-		remrunqueue(td);
-		setrunqueue(td);
+		adjustrunqueue(td, prio);
+	} else {
+		td->td_priority = prio;
 	}
 }
 
@@ -527,6 +511,7 @@ sched_switchout(struct thread *td)
 	KASSERT((ke->ke_state == KES_THREAD), ("mi_switch: kse state?"));
 
 	td->td_lastcpu = ke->ke_oncpu;
+	td->td_last_kse = ke;
 	ke->ke_oncpu = NOCPU;
 	ke->ke_flags &= ~KEF_NEEDRESCHED;
 	/*

sys/posix4/ksched.c

@@ -187,10 +187,7 @@ int ksched_setscheduler(register_t *ret, struct ksched *ksched,
 					td->td_kse->ke_flags |= KEF_NEEDRESCHED;
 				} else if (TD_ON_RUNQ(td)) {
 					if (td->td_priority > kg->kg_user_pri) {
-						remrunqueue(td);
-						td->td_priority =
-						    kg->kg_user_pri;
-						setrunqueue(td);
+						sched_prio(td, kg->kg_user_pri);
 					}
 				}
 			}
@@ -220,10 +217,7 @@ int ksched_setscheduler(register_t *ret, struct ksched *ksched,
 					td->td_kse->ke_flags |= KEF_NEEDRESCHED;
 				} else if (TD_ON_RUNQ(td)) {
 					if (td->td_priority > kg->kg_user_pri) {
-						remrunqueue(td);
-						td->td_priority =
-						    kg->kg_user_pri;
-						setrunqueue(td);
+						sched_prio(td, kg->kg_user_pri);
 					}
 				}
 				

sys/sys/proc.h

@@ -268,8 +268,8 @@ struct thread {
 #define	td_startzero td_flags
 	int		td_flags;	/* (j) TDF_* flags. */
 	int		td_inhibitors;	/* (j) Why can not run */
-	struct kse	*td_last_kse;	/* Where it wants to be if possible. */
-	struct kse	*td_kse;	/* Current KSE if running. */
+	struct kse	*td_last_kse;	/* (j) Previous value of td_kse */
+	struct kse	*td_kse;	/* (j) Current KSE if running. */
 	int		td_dupfd;	/* (k) Ret value from fdopen. XXX */
 	void		*td_wchan;	/* (j) Sleep address. */
 	const char	*td_wmesg;	/* (j) Reason for sleep. */
@@ -844,6 +844,7 @@ struct	proc *pfind(pid_t);	/* Find process by id. */
 struct	pgrp *pgfind(pid_t);	/* Find process group by id. */
 struct	proc *zpfind(pid_t);	/* Find zombie process by id. */
 
+void	adjustrunqueue(struct thread *, int newpri);
 void	ast(struct trapframe *framep);
 struct	thread *choosethread(void);
 int	cr_cansignal(struct ucred *cred, struct proc *proc, int signum);
@@ -871,7 +872,6 @@ void	threadinit(void);
 void	proc_linkup(struct proc *p, struct ksegrp *kg,
 	    struct kse *ke, struct thread *td);
 void	proc_reparent(struct proc *child, struct proc *newparent);
-void	remrunqueue(struct thread *);
 int	securelevel_ge(struct ucred *cr, int level);
 int	securelevel_gt(struct ucred *cr, int level);
 void	setrunnable(struct thread *);