xref: /freebsd/sys/kern/kern_switch.c (revision 33c06e1d3e788fa9d439855054e990c0acef8053)
1 /*
2  * Copyright (c) 2001 Jake Burkholder <jake@FreeBSD.org>
3  * All rights reserved.
4  *
5  * Redistribution and use in source and binary forms, with or without
6  * modification, are permitted provided that the following conditions
7  * are met:
8  * 1. Redistributions of source code must retain the above copyright
9  *    notice, this list of conditions and the following disclaimer.
10  * 2. Redistributions in binary form must reproduce the above copyright
11  *    notice, this list of conditions and the following disclaimer in the
12  *    documentation and/or other materials provided with the distribution.
13  *
14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24  * SUCH DAMAGE.
25  *
26  * $FreeBSD$
27  */
28 
29 /***
30 
31 Here is the logic..
32 
33 If there are N processors, then there are at most N KSEs (kernel
34 schedulable entities) working to process threads that belong to a
35 KSEGOUP (kg). If there are X of these KSEs actually running at the
36 moment in question, then there are at most M (N-X) of these KSEs on
37 the run queue, as running KSEs are not on the queue.
38 
39 Runnable threads are queued off the KSEGROUP in priority order.
40 If there are M or more threads runnable, the top M threads
41 (by priority) are 'preassigned' to the M KSEs not running. The KSEs take
42 their priority from those threads and are put on the run queue.
43 
44 The last thread that had a priority high enough to have a KSE associated
45 with it, AND IS ON THE RUN QUEUE is pointed to by
46 kg->kg_last_assigned. If no threads queued off the KSEGROUP have KSEs
47 assigned as all the available KSEs are activly running, or because there
48 are no threads queued, that pointer is NULL.
49 
50 When a KSE is removed from the run queue to become runnable, we know
51 it was associated with the highest priority thread in the queue (at the head
52 of the queue). If it is also the last assigned we know M was 1 and must
53 now be 0. Since the thread is no longer queued that pointer must be
54 removed from it. Since we know there were no more KSEs available,
55 (M was 1 and is now 0) and since we are not FREEING our KSE
56 but using it, we know there are STILL no more KSEs available, we can prove
57 that the next thread in the ksegrp list will not have a KSE to assign to
58 it, so we can show that the pointer must be made 'invalid' (NULL).
59 
60 The pointer exists so that when a new thread is made runnable, it can
61 have its priority compared with the last assigned thread to see if
62 it should 'steal' its KSE or not.. i.e. is it 'earlier'
63 on the list than that thread or later.. If it's earlier, then the KSE is
64 removed from the last assigned (which is now not assigned a KSE)
65 and reassigned to the new thread, which is placed earlier in the list.
66 The pointer is then backed up to the previous thread (which may or may not
67 be the new thread).
68 
69 When a thread sleeps or is removed, the KSE becomes available and if there
70 are queued threads that are not assigned KSEs, the highest priority one of
71 them is assigned the KSE, which is then placed back on the run queue at
72 the approipriate place, and the kg->kg_last_assigned pointer is adjusted down
73 to point to it.
74 
75 The following diagram shows 2 KSEs and 3 threads from a single process.
76 
77  RUNQ: --->KSE---KSE--...    (KSEs queued at priorities from threads)
78               \    \____
79                \        \
80     KSEGROUP---thread--thread--thread    (queued in priority order)
81         \                 /
82          \_______________/
83           (last_assigned)
84 
85 The result of this scheme is that the M available KSEs are always
86 queued at the priorities they have inherrited from the M highest priority
87 threads for that KSEGROUP. If this situation changes, the KSEs are
88 reassigned to keep this true.
89 
90 */
91 
92 #include <sys/param.h>
93 #include <sys/systm.h>
94 #include <sys/kernel.h>
95 #include <sys/ktr.h>
96 #include <sys/lock.h>
97 #include <sys/mutex.h>
98 #include <sys/proc.h>
99 #include <sys/queue.h>
100 #include <machine/critical.h>
101 
102 CTASSERT((RQB_BPW * RQB_LEN) == RQ_NQS);
103 
104 /*
105  * Global run queue.
106  */
107 static struct runq runq;
108 SYSINIT(runq, SI_SUB_RUN_QUEUE, SI_ORDER_FIRST, runq_init, &runq)
109 
110 static void runq_readjust(struct runq *rq, struct kse *ke);
111 /************************************************************************
112  * Functions that manipulate runnability from a thread perspective.	*
113  ************************************************************************/
114 
115 /*
116  * Select the KSE that will be run next.  From that find the thread, and x
117  * remove it from the KSEGRP's run queue.  If there is thread clustering,
118  * this will be what does it.
119  */
120 struct thread *
121 choosethread(void)
122 {
123 	struct kse *ke;
124 	struct thread *td;
125 	struct ksegrp *kg;
126 
127 retry:
128 	if ((ke = runq_choose(&runq))) {
129 		td = ke->ke_thread;
130 		KASSERT((td->td_kse == ke), ("kse/thread mismatch"));
131 		kg = ke->ke_ksegrp;
132 		if (td->td_flags & TDF_UNBOUND) {
133 			TAILQ_REMOVE(&kg->kg_runq, td, td_runq);
134 			if (kg->kg_last_assigned == td) {
135 				if (TAILQ_PREV(td, threadqueue, td_runq)
136 				    != NULL)
137 					printf("Yo MAMA!\n");
138 				kg->kg_last_assigned = TAILQ_PREV(td,
139 				    threadqueue, td_runq);
140 			}
141 			/*
142 			 *  If we have started running an upcall,
143 			 * Then TDF_UNBOUND WAS set because the thread was
144 			 * created without a KSE. Now that we have one,
145 			 * and it is our time to run, we make sure
146 			 * that BOUND semantics apply for the rest of
147 			 * the journey to userland, and into the UTS.
148 			 */
149 #ifdef	NOTYET
150 			if (td->td_flags & TDF_UPCALLING)
151 				tdf->td_flags &= ~TDF_UNBOUND;
152 #endif
153 		}
154 		kg->kg_runnable--;
155 		CTR2(KTR_RUNQ, "choosethread: td=%p pri=%d",
156 		    td, td->td_priority);
157 	} else {
158 		/* Simulate runq_choose() having returned the idle thread */
159 		td = PCPU_GET(idlethread);
160 		ke = td->td_kse;
161 		CTR1(KTR_RUNQ, "choosethread: td=%p (idle)", td);
162 	}
163 	ke->ke_flags |= KEF_DIDRUN;
164 	if (panicstr && ((td->td_proc->p_flag & P_SYSTEM) == 0 &&
165 	    (td->td_flags & TDF_INPANIC) == 0))
166 		goto retry;
167 	TD_SET_RUNNING(td);
168 	return (td);
169 }
170 
171 /*
172  * Given a KSE (now surplus), either assign a new runable thread to it
173  * (and put it in the run queue) or put it in the ksegrp's idle KSE list.
174  * Assumes the kse is not linked to any threads any more. (has been cleaned).
175  */
176 void
177 kse_reassign(struct kse *ke)
178 {
179 	struct ksegrp *kg;
180 	struct thread *td;
181 
182 	mtx_assert(&sched_lock, MA_OWNED);
183 	kg = ke->ke_ksegrp;
184 
185 	/*
186 	 * Find the first unassigned thread
187 	 * If there is a 'last assigned' then see what's next.
188 	 * otherwise look at what is first.
189 	 */
190 	if ((td = kg->kg_last_assigned)) {
191 		td = TAILQ_NEXT(td, td_runq);
192 	} else {
193 		td = TAILQ_FIRST(&kg->kg_runq);
194 	}
195 
196 	/*
197 	 * If we found one assign it the kse, otherwise idle the kse.
198 	 */
199 	if (td) {
200 		kg->kg_last_assigned = td;
201 		td->td_kse = ke;
202 		ke->ke_thread = td;
203 		runq_add(&runq, ke);
204 		CTR2(KTR_RUNQ, "kse_reassign: ke%p -> td%p", ke, td);
205 	} else {
206 		ke->ke_state = KES_IDLE;
207 		ke->ke_thread = NULL;
208 		TAILQ_INSERT_HEAD(&kg->kg_iq, ke, ke_kgrlist);
209 		kg->kg_idle_kses++;
210 		CTR1(KTR_RUNQ, "kse_reassign: ke%p idled", ke);
211 	}
212 }
213 
214 int
215 kserunnable(void)
216 {
217 	return runq_check(&runq);
218 }
219 
220 /*
221  * Remove a thread from its KSEGRP's run queue.
222  * This in turn may remove it from a KSE if it was already assigned
223  * to one, possibly causing a new thread to be assigned to the KSE
224  * and the KSE getting a new priority (unless it's a BOUND thread/KSE pair).
225  */
226 void
227 remrunqueue(struct thread *td)
228 {
229 	struct thread *td2, *td3;
230 	struct ksegrp *kg;
231 	struct kse *ke;
232 
233 	mtx_assert(&sched_lock, MA_OWNED);
234 	KASSERT ((TD_ON_RUNQ(td)), ("remrunqueue: Bad state on run queue"));
235 	kg = td->td_ksegrp;
236 	ke = td->td_kse;
237 	/*
238 	 * If it's a bound thread/KSE pair, take the shortcut. All non-KSE
239 	 * threads are BOUND.
240 	 */
241 	CTR1(KTR_RUNQ, "remrunqueue: td%p", td);
242 	kg->kg_runnable--;
243 	TD_SET_CAN_RUN(td);
244 	if ((td->td_flags & TDF_UNBOUND) == 0)  {
245 		/* Bring its kse with it, leave the thread attached */
246 		runq_remove(&runq, ke);
247 		ke->ke_state = KES_THREAD;
248 		return;
249 	}
250 	if (ke) {
251 		/*
252 		 * This thread has been assigned to a KSE.
253 		 * We need to dissociate it and try assign the
254 		 * KSE to the next available thread. Then, we should
255 		 * see if we need to move the KSE in the run queues.
256 		 */
257 		td2 = kg->kg_last_assigned;
258 		KASSERT((td2 != NULL), ("last assigned has wrong value "));
259 		td->td_kse = NULL;
260 		if ((td3 = TAILQ_NEXT(td2, td_runq))) {
261 			KASSERT(td3 != td, ("td3 somehow matched td"));
262 			/*
263 			 * Give the next unassigned thread to the KSE
264 			 * so the number of runnable KSEs remains
265 			 * constant.
266 			 */
267 			td3->td_kse = ke;
268 			ke->ke_thread = td3;
269 			kg->kg_last_assigned = td3;
270 			runq_readjust(&runq, ke);
271 		} else {
272 			/*
273 			 * There is no unassigned thread.
274 			 * If we were the last assigned one,
275 			 * adjust the last assigned pointer back
276 			 * one, which may result in NULL.
277 			 */
278 			if (td == td2) {
279 				kg->kg_last_assigned =
280 				    TAILQ_PREV(td, threadqueue, td_runq);
281 			}
282 			runq_remove(&runq, ke);
283 			KASSERT((ke->ke_state != KES_IDLE),
284 			    ("kse already idle"));
285 			ke->ke_state = KES_IDLE;
286 			ke->ke_thread = NULL;
287 			TAILQ_INSERT_HEAD(&kg->kg_iq, ke, ke_kgrlist);
288 			kg->kg_idle_kses++;
289 		}
290 	}
291 	TAILQ_REMOVE(&kg->kg_runq, td, td_runq);
292 }
293 
294 void
295 setrunqueue(struct thread *td)
296 {
297 	struct kse *ke;
298 	struct ksegrp *kg;
299 	struct thread *td2;
300 	struct thread *tda;
301 
302 	CTR1(KTR_RUNQ, "setrunqueue: td%p", td);
303 	mtx_assert(&sched_lock, MA_OWNED);
304 	KASSERT((TD_CAN_RUN(td) || TD_IS_RUNNING(td)),
305 	    ("setrunqueue: bad thread state"));
306 	TD_SET_RUNQ(td);
307 	kg = td->td_ksegrp;
308 	kg->kg_runnable++;
309 	if ((td->td_flags & TDF_UNBOUND) == 0) {
310 		KASSERT((td->td_kse != NULL),
311 		    ("queueing BAD thread to run queue"));
312 		/*
313 		 * Common path optimisation: Only one of everything
314 		 * and the KSE is always already attached.
315 		 * Totally ignore the ksegrp run queue.
316 		 */
317 		runq_add(&runq, td->td_kse);
318 		return;
319 	}
320 	/*
321 	 * Ok, so we are threading with this thread.
322 	 * We don't have a KSE, see if we can get one..
323 	 */
324 	tda = kg->kg_last_assigned;
325 	if ((ke = td->td_kse) == NULL) {
326 		/*
327 		 * We will need a KSE, see if there is one..
328 		 * First look for a free one, before getting desperate.
329 		 * If we can't get one, our priority is not high enough..
330 		 * that's ok..
331 		 */
332 		if (kg->kg_idle_kses) {
333 			/*
334 			 * There is a free one so it's ours for the asking..
335 			 */
336 			ke = TAILQ_FIRST(&kg->kg_iq);
337 			TAILQ_REMOVE(&kg->kg_iq, ke, ke_kgrlist);
338 			ke->ke_state = KES_THREAD;
339 			kg->kg_idle_kses--;
340 		} else if (tda && (tda->td_priority > td->td_priority)) {
341 			/*
342 			 * None free, but there is one we can commandeer.
343 			 */
344 			ke = tda->td_kse;
345 			tda->td_kse = NULL;
346 			ke->ke_thread = NULL;
347 			tda = kg->kg_last_assigned =
348 		    	    TAILQ_PREV(tda, threadqueue, td_runq);
349 			runq_remove(&runq, ke);
350 		}
351 	} else {
352 		/*
353 		 * Temporarily disassociate so it looks like the other cases.
354 		 */
355 		ke->ke_thread = NULL;
356 		td->td_kse = NULL;
357 	}
358 
359 	/*
360 	 * Add the thread to the ksegrp's run queue at
361 	 * the appropriate place.
362 	 */
363 	TAILQ_FOREACH(td2, &kg->kg_runq, td_runq) {
364 		if (td2->td_priority > td->td_priority) {
365 			TAILQ_INSERT_BEFORE(td2, td, td_runq);
366 			break;
367 		}
368 	}
369 	if (td2 == NULL) {
370 		/* We ran off the end of the TAILQ or it was empty. */
371 		TAILQ_INSERT_TAIL(&kg->kg_runq, td, td_runq);
372 	}
373 
374 	/*
375 	 * If we have a ke to use, then put it on the run queue and
376 	 * If needed, readjust the last_assigned pointer.
377 	 */
378 	if (ke) {
379 		if (tda == NULL) {
380 			/*
381 			 * No pre-existing last assigned so whoever is first
382 			 * gets the KSE we brought in.. (maybe us)
383 			 */
384 			td2 = TAILQ_FIRST(&kg->kg_runq);
385 			KASSERT((td2->td_kse == NULL),
386 			    ("unexpected ke present"));
387 			td2->td_kse = ke;
388 			ke->ke_thread = td2;
389 			kg->kg_last_assigned = td2;
390 		} else if (tda->td_priority > td->td_priority) {
391 			/*
392 			 * It's ours, grab it, but last_assigned is past us
393 			 * so don't change it.
394 			 */
395 			td->td_kse = ke;
396 			ke->ke_thread = td;
397 		} else {
398 			/*
399 			 * We are past last_assigned, so
400 			 * put the new kse on whatever is next,
401 			 * which may or may not be us.
402 			 */
403 			td2 = TAILQ_NEXT(tda, td_runq);
404 			kg->kg_last_assigned = td2;
405 			td2->td_kse = ke;
406 			ke->ke_thread = td2;
407 		}
408 		runq_add(&runq, ke);
409 	}
410 }
411 
412 /************************************************************************
413  * Critical section marker functions					*
414  ************************************************************************/
415 /* Critical sections that prevent preemption. */
416 void
417 critical_enter(void)
418 {
419 	struct thread *td;
420 
421 	td = curthread;
422 	if (td->td_critnest == 0)
423 		cpu_critical_enter();
424 	td->td_critnest++;
425 }
426 
427 void
428 critical_exit(void)
429 {
430 	struct thread *td;
431 
432 	td = curthread;
433 	if (td->td_critnest == 1) {
434 		td->td_critnest = 0;
435 		cpu_critical_exit();
436 	} else {
437 		td->td_critnest--;
438 	}
439 }
440 
441 
442 /************************************************************************
443  * SYSTEM RUN QUEUE manipulations and tests				*
444  ************************************************************************/
445 /*
446  * Initialize a run structure.
447  */
448 void
449 runq_init(struct runq *rq)
450 {
451 	int i;
452 
453 	bzero(rq, sizeof *rq);
454 	for (i = 0; i < RQ_NQS; i++)
455 		TAILQ_INIT(&rq->rq_queues[i]);
456 }
457 
458 /*
459  * Clear the status bit of the queue corresponding to priority level pri,
460  * indicating that it is empty.
461  */
462 static __inline void
463 runq_clrbit(struct runq *rq, int pri)
464 {
465 	struct rqbits *rqb;
466 
467 	rqb = &rq->rq_status;
468 	CTR4(KTR_RUNQ, "runq_clrbit: bits=%#x %#x bit=%#x word=%d",
469 	    rqb->rqb_bits[RQB_WORD(pri)],
470 	    rqb->rqb_bits[RQB_WORD(pri)] & ~RQB_BIT(pri),
471 	    RQB_BIT(pri), RQB_WORD(pri));
472 	rqb->rqb_bits[RQB_WORD(pri)] &= ~RQB_BIT(pri);
473 }
474 
475 /*
476  * Find the index of the first non-empty run queue.  This is done by
477  * scanning the status bits, a set bit indicates a non-empty queue.
478  */
479 static __inline int
480 runq_findbit(struct runq *rq)
481 {
482 	struct rqbits *rqb;
483 	int pri;
484 	int i;
485 
486 	rqb = &rq->rq_status;
487 	for (i = 0; i < RQB_LEN; i++)
488 		if (rqb->rqb_bits[i]) {
489 			pri = RQB_FFS(rqb->rqb_bits[i]) + (i << RQB_L2BPW);
490 			CTR3(KTR_RUNQ, "runq_findbit: bits=%#x i=%d pri=%d",
491 			    rqb->rqb_bits[i], i, pri);
492 			return (pri);
493 		}
494 
495 	return (-1);
496 }
497 
498 /*
499  * Set the status bit of the queue corresponding to priority level pri,
500  * indicating that it is non-empty.
501  */
502 static __inline void
503 runq_setbit(struct runq *rq, int pri)
504 {
505 	struct rqbits *rqb;
506 
507 	rqb = &rq->rq_status;
508 	CTR4(KTR_RUNQ, "runq_setbit: bits=%#x %#x bit=%#x word=%d",
509 	    rqb->rqb_bits[RQB_WORD(pri)],
510 	    rqb->rqb_bits[RQB_WORD(pri)] | RQB_BIT(pri),
511 	    RQB_BIT(pri), RQB_WORD(pri));
512 	rqb->rqb_bits[RQB_WORD(pri)] |= RQB_BIT(pri);
513 }
514 
515 /*
516  * Add the KSE to the queue specified by its priority, and set the
517  * corresponding status bit.
518  */
519 void
520 runq_add(struct runq *rq, struct kse *ke)
521 {
522 	struct rqhead *rqh;
523 	int pri;
524 
525 	mtx_assert(&sched_lock, MA_OWNED);
526 	KASSERT((ke->ke_thread != NULL), ("runq_add: No thread on KSE"));
527 	KASSERT((ke->ke_thread->td_kse != NULL),
528 	    ("runq_add: No KSE on thread"));
529 	KASSERT(ke->ke_state != KES_ONRUNQ,
530 	    ("runq_add: kse %p (%s) already in run queue", ke,
531 	    ke->ke_proc->p_comm));
532 	KASSERT(ke->ke_proc->p_sflag & PS_INMEM,
533 		("runq_add: process swapped out"));
534 	pri = ke->ke_thread->td_priority / RQ_PPQ;
535 	ke->ke_rqindex = pri;
536 	runq_setbit(rq, pri);
537 	rqh = &rq->rq_queues[pri];
538 	CTR4(KTR_RUNQ, "runq_add: p=%p pri=%d %d rqh=%p",
539 	    ke->ke_proc, ke->ke_thread->td_priority, pri, rqh);
540 	TAILQ_INSERT_TAIL(rqh, ke, ke_procq);
541 	ke->ke_ksegrp->kg_runq_kses++;
542 	ke->ke_state = KES_ONRUNQ;
543 }
544 
545 /*
546  * Return true if there are runnable processes of any priority on the run
547  * queue, false otherwise.  Has no side effects, does not modify the run
548  * queue structure.
549  */
550 int
551 runq_check(struct runq *rq)
552 {
553 	struct rqbits *rqb;
554 	int i;
555 
556 	rqb = &rq->rq_status;
557 	for (i = 0; i < RQB_LEN; i++)
558 		if (rqb->rqb_bits[i]) {
559 			CTR2(KTR_RUNQ, "runq_check: bits=%#x i=%d",
560 			    rqb->rqb_bits[i], i);
561 			return (1);
562 		}
563 	CTR0(KTR_RUNQ, "runq_check: empty");
564 
565 	return (0);
566 }
567 
568 /*
569  * Find and remove the highest priority process from the run queue.
570  * If there are no runnable processes, the per-cpu idle process is
571  * returned.  Will not return NULL under any circumstances.
572  */
573 struct kse *
574 runq_choose(struct runq *rq)
575 {
576 	struct rqhead *rqh;
577 	struct kse *ke;
578 	int pri;
579 
580 	mtx_assert(&sched_lock, MA_OWNED);
581 	while ((pri = runq_findbit(rq)) != -1) {
582 		rqh = &rq->rq_queues[pri];
583 		ke = TAILQ_FIRST(rqh);
584 		KASSERT(ke != NULL, ("runq_choose: no proc on busy queue"));
585 		CTR3(KTR_RUNQ,
586 		    "runq_choose: pri=%d kse=%p rqh=%p", pri, ke, rqh);
587 		TAILQ_REMOVE(rqh, ke, ke_procq);
588 		ke->ke_ksegrp->kg_runq_kses--;
589 		if (TAILQ_EMPTY(rqh)) {
590 			CTR0(KTR_RUNQ, "runq_choose: empty");
591 			runq_clrbit(rq, pri);
592 		}
593 
594 		ke->ke_state = KES_THREAD;
595 		KASSERT((ke->ke_thread != NULL),
596 		    ("runq_choose: No thread on KSE"));
597 		KASSERT((ke->ke_thread->td_kse != NULL),
598 		    ("runq_choose: No KSE on thread"));
599 		KASSERT(ke->ke_proc->p_sflag & PS_INMEM,
600 			("runq_choose: process swapped out"));
601 		return (ke);
602 	}
603 	CTR1(KTR_RUNQ, "runq_choose: idleproc pri=%d", pri);
604 
605 	return (NULL);
606 }
607 
608 /*
609  * Remove the KSE from the queue specified by its priority, and clear the
610  * corresponding status bit if the queue becomes empty.
611  * Caller must set ke->ke_state afterwards.
612  */
613 void
614 runq_remove(struct runq *rq, struct kse *ke)
615 {
616 	struct rqhead *rqh;
617 	int pri;
618 
619 	KASSERT((ke->ke_state == KES_ONRUNQ), ("KSE not on run queue"));
620 	mtx_assert(&sched_lock, MA_OWNED);
621 	KASSERT(ke->ke_proc->p_sflag & PS_INMEM,
622 		("runq_remove: process swapped out"));
623 	pri = ke->ke_rqindex;
624 	rqh = &rq->rq_queues[pri];
625 	CTR4(KTR_RUNQ, "runq_remove: p=%p pri=%d %d rqh=%p",
626 	    ke, ke->ke_thread->td_priority, pri, rqh);
627 	KASSERT(ke != NULL, ("runq_remove: no proc on busy queue"));
628 	TAILQ_REMOVE(rqh, ke, ke_procq);
629 	if (TAILQ_EMPTY(rqh)) {
630 		CTR0(KTR_RUNQ, "runq_remove: empty");
631 		runq_clrbit(rq, pri);
632 	}
633 	ke->ke_state = KES_THREAD;
634 	ke->ke_ksegrp->kg_runq_kses--;
635 }
636 
637 static void
638 runq_readjust(struct runq *rq, struct kse *ke)
639 {
640 
641 	if (ke->ke_rqindex != (ke->ke_thread->td_priority / RQ_PPQ)) {
642 		runq_remove(rq, ke);
643 		runq_add(rq, ke);
644 	}
645 }
646 
647 #if 0
648 void
649 thread_sanity_check(struct thread *td)
650 {
651 	struct proc *p;
652 	struct ksegrp *kg;
653 	struct kse *ke;
654 	struct thread *td2;
655 	unsigned int prevpri;
656 	int	saw_lastassigned;
657 	int unassigned;
658 	int assigned;
659 
660 	p = td->td_proc;
661 	kg = td->td_ksegrp;
662 	ke = td->td_kse;
663 
664 
665 	if (ke) {
666 		if (p != ke->ke_proc) {
667 			panic("wrong proc");
668 		}
669 		if (ke->ke_thread != td) {
670 			panic("wrong thread");
671 		}
672 	}
673 
674 	if ((p->p_flag & P_KSES) == 0) {
675 		if (ke == NULL) {
676 			panic("non KSE thread lost kse");
677 		}
678 	} else {
679 		prevpri = 0;
680 		saw_lastassigned = 0;
681 		unassigned = 0;
682 		assigned = 0;
683 		TAILQ_FOREACH(td2, &kg->kg_runq, td_runq) {
684 			if (td2->td_priority < prevpri) {
685 				panic("thread runqueue unosorted");
686 			}
687 			prevpri = td2->td_priority;
688 			if (td2->td_kse) {
689 				assigned++;
690 				if (unassigned) {
691 					panic("unassigned before assigned");
692 				}
693  				if  (kg->kg_last_assigned == NULL) {
694 					panic("lastassigned corrupt");
695 				}
696 				if (saw_lastassigned) {
697 					panic("last assigned not last");
698 				}
699 				if (td2->td_kse->ke_thread != td2) {
700 					panic("mismatched kse/thread");
701 				}
702 			} else {
703 				unassigned++;
704 			}
705 			if (td2 == kg->kg_last_assigned) {
706 				saw_lastassigned = 1;
707 				if (td2->td_kse == NULL) {
708 					panic("last assigned not assigned");
709 				}
710 			}
711 		}
712 		if (kg->kg_last_assigned && (saw_lastassigned == 0)) {
713 			panic("where on earth does lastassigned point?");
714 		}
715 		FOREACH_THREAD_IN_GROUP(kg, td2) {
716 			if (((td2->td_flags & TDF_UNBOUND) == 0) &&
717 			    (TD_ON_RUNQ(td2))) {
718 				assigned++;
719 				if (td2->td_kse == NULL) {
720 					panic ("BOUND thread with no KSE");
721 				}
722 			}
723 		}
724 #if 0
725 		if ((unassigned + assigned) != kg->kg_runnable) {
726 			panic("wrong number in runnable");
727 		}
728 #endif
729 	}
730 }
731 #endif
732 
733