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
27 /***
28 Here is the logic..
29
30 If there are N processors, then there are at most N KSEs (kernel
31 schedulable entities) working to process threads that belong to a
32 KSEGROUP (kg). If there are X of these KSEs actually running at the
33 moment in question, then there are at most M (N-X) of these KSEs on
34 the run queue, as running KSEs are not on the queue.
35
36 Runnable threads are queued off the KSEGROUP in priority order.
37 If there are M or more threads runnable, the top M threads
38 (by priority) are 'preassigned' to the M KSEs not running. The KSEs take
39 their priority from those threads and are put on the run queue.
40
41 The last thread that had a priority high enough to have a KSE associated
42 with it, AND IS ON THE RUN QUEUE is pointed to by
43 kg->kg_last_assigned. If no threads queued off the KSEGROUP have KSEs
44 assigned as all the available KSEs are activly running, or because there
45 are no threads queued, that pointer is NULL.
46
47 When a KSE is removed from the run queue to become runnable, we know
48 it was associated with the highest priority thread in the queue (at the head
49 of the queue). If it is also the last assigned we know M was 1 and must
50 now be 0. Since the thread is no longer queued that pointer must be
51 removed from it. Since we know there were no more KSEs available,
52 (M was 1 and is now 0) and since we are not FREEING our KSE
53 but using it, we know there are STILL no more KSEs available, we can prove
54 that the next thread in the ksegrp list will not have a KSE to assign to
55 it, so we can show that the pointer must be made 'invalid' (NULL).
56
57 The pointer exists so that when a new thread is made runnable, it can
58 have its priority compared with the last assigned thread to see if
59 it should 'steal' its KSE or not.. i.e. is it 'earlier'
60 on the list than that thread or later.. If it's earlier, then the KSE is
61 removed from the last assigned (which is now not assigned a KSE)
62 and reassigned to the new thread, which is placed earlier in the list.
63 The pointer is then backed up to the previous thread (which may or may not
64 be the new thread).
65
66 When a thread sleeps or is removed, the KSE becomes available and if there
67 are queued threads that are not assigned KSEs, the highest priority one of
68 them is assigned the KSE, which is then placed back on the run queue at
69 the approipriate place, and the kg->kg_last_assigned pointer is adjusted down
70 to point to it.
71
72 The following diagram shows 2 KSEs and 3 threads from a single process.
73
74 RUNQ: --->KSE---KSE--... (KSEs queued at priorities from threads)
75 \ \____
76 \ \
77 KSEGROUP---thread--thread--thread (queued in priority order)
78 \ /
79 \_______________/
80 (last_assigned)
81
82 The result of this scheme is that the M available KSEs are always
83 queued at the priorities they have inherrited from the M highest priority
84 threads for that KSEGROUP. If this situation changes, the KSEs are
85 reassigned to keep this true.
86 ***/
87
88 #include <sys/cdefs.h>
89 __FBSDID("$FreeBSD: releng/5.3/sys/kern/kern_switch.c 136789 2004-10-22 19:13:07Z scottl $");
90
91 #include "opt_sched.h"
92
93 #ifndef KERN_SWITCH_INCLUDE
94 #include <sys/param.h>
95 #include <sys/systm.h>
96 #include <sys/kdb.h>
97 #include <sys/kernel.h>
98 #include <sys/ktr.h>
99 #include <sys/lock.h>
100 #include <sys/mutex.h>
101 #include <sys/proc.h>
102 #include <sys/queue.h>
103 #include <sys/sched.h>
104 #else /* KERN_SWITCH_INCLUDE */
105 #if defined(SMP) && (defined(__i386__) || defined(__amd64__))
106 #include <sys/smp.h>
107 #endif
108 #include <machine/critical.h>
109 #if defined(SMP) && defined(SCHED_4BSD)
110 #include <sys/sysctl.h>
111 #endif
112
113 #ifdef FULL_PREEMPTION
114 #ifndef PREEMPTION
115 #error "The FULL_PREEMPTION option requires the PREEMPTION option"
116 #endif
117 #endif
118
119 CTASSERT((RQB_BPW * RQB_LEN) == RQ_NQS);
120
121 #define td_kse td_sched
122
123 /************************************************************************
124 * Functions that manipulate runnability from a thread perspective. *
125 ************************************************************************/
126 /*
127 * Select the KSE that will be run next. From that find the thread, and
128 * remove it from the KSEGRP's run queue. If there is thread clustering,
129 * this will be what does it.
130 */
131 struct thread *
132 choosethread(void)
133 {
134 struct kse *ke;
135 struct thread *td;
136 struct ksegrp *kg;
137
138 #if defined(SMP) && (defined(__i386__) || defined(__amd64__))
139 if (smp_active == 0 && PCPU_GET(cpuid) != 0) {
140 /* Shutting down, run idlethread on AP's */
141 td = PCPU_GET(idlethread);
142 ke = td->td_kse;
143 CTR1(KTR_RUNQ, "choosethread: td=%p (idle)", td);
144 ke->ke_flags |= KEF_DIDRUN;
145 TD_SET_RUNNING(td);
146 return (td);
147 }
148 #endif
149
150 retry:
151 ke = sched_choose();
152 if (ke) {
153 td = ke->ke_thread;
154 KASSERT((td->td_kse == ke), ("kse/thread mismatch"));
155 kg = ke->ke_ksegrp;
156 if (td->td_proc->p_flag & P_HADTHREADS) {
157 if (kg->kg_last_assigned == td) {
158 kg->kg_last_assigned = TAILQ_PREV(td,
159 threadqueue, td_runq);
160 }
161 TAILQ_REMOVE(&kg->kg_runq, td, td_runq);
162 kg->kg_runnable--;
163 }
164 CTR2(KTR_RUNQ, "choosethread: td=%p pri=%d",
165 td, td->td_priority);
166 } else {
167 /* Simulate runq_choose() having returned the idle thread */
168 td = PCPU_GET(idlethread);
169 ke = td->td_kse;
170 CTR1(KTR_RUNQ, "choosethread: td=%p (idle)", td);
171 }
172 ke->ke_flags |= KEF_DIDRUN;
173
174 /*
175 * If we are in panic, only allow system threads,
176 * plus the one we are running in, to be run.
177 */
178 if (panicstr && ((td->td_proc->p_flag & P_SYSTEM) == 0 &&
179 (td->td_flags & TDF_INPANIC) == 0)) {
180 /* note that it is no longer on the run queue */
181 TD_SET_CAN_RUN(td);
182 goto retry;
183 }
184
185 TD_SET_RUNNING(td);
186 return (td);
187 }
188
189 /*
190 * Given a surplus system slot, try assign a new runnable thread to it.
191 * Called from:
192 * sched_thread_exit() (local)
193 * sched_switch() (local)
194 * sched_thread_exit() (local)
195 * remrunqueue() (local) (not at the moment)
196 */
197 static void
198 slot_fill(struct ksegrp *kg)
199 {
200 struct thread *td;
201
202 mtx_assert(&sched_lock, MA_OWNED);
203 while (kg->kg_avail_opennings > 0) {
204 /*
205 * Find the first unassigned thread
206 */
207 if ((td = kg->kg_last_assigned) != NULL)
208 td = TAILQ_NEXT(td, td_runq);
209 else
210 td = TAILQ_FIRST(&kg->kg_runq);
211
212 /*
213 * If we found one, send it to the system scheduler.
214 */
215 if (td) {
216 kg->kg_last_assigned = td;
217 sched_add(td, SRQ_YIELDING);
218 CTR2(KTR_RUNQ, "slot_fill: td%p -> kg%p", td, kg);
219 } else {
220 /* no threads to use up the slots. quit now */
221 break;
222 }
223 }
224 }
225
226 #ifdef SCHED_4BSD
227 /*
228 * Remove a thread from its KSEGRP's run queue.
229 * This in turn may remove it from a KSE if it was already assigned
230 * to one, possibly causing a new thread to be assigned to the KSE
231 * and the KSE getting a new priority.
232 */
233 static void
234 remrunqueue(struct thread *td)
235 {
236 struct thread *td2, *td3;
237 struct ksegrp *kg;
238 struct kse *ke;
239
240 mtx_assert(&sched_lock, MA_OWNED);
241 KASSERT((TD_ON_RUNQ(td)), ("remrunqueue: Bad state on run queue"));
242 kg = td->td_ksegrp;
243 ke = td->td_kse;
244 CTR1(KTR_RUNQ, "remrunqueue: td%p", td);
245 TD_SET_CAN_RUN(td);
246 /*
247 * If it is not a threaded process, take the shortcut.
248 */
249 if ((td->td_proc->p_flag & P_HADTHREADS) == 0) {
250 /* remve from sys run queue and free up a slot */
251 sched_rem(td);
252 ke->ke_state = KES_THREAD;
253 return;
254 }
255 td3 = TAILQ_PREV(td, threadqueue, td_runq);
256 TAILQ_REMOVE(&kg->kg_runq, td, td_runq);
257 kg->kg_runnable--;
258 if (ke->ke_state == KES_ONRUNQ) {
259 /*
260 * This thread has been assigned to the system run queue.
261 * We need to dissociate it and try assign the
262 * KSE to the next available thread. Then, we should
263 * see if we need to move the KSE in the run queues.
264 */
265 sched_rem(td);
266 ke->ke_state = KES_THREAD;
267 td2 = kg->kg_last_assigned;
268 KASSERT((td2 != NULL), ("last assigned has wrong value"));
269 if (td2 == td)
270 kg->kg_last_assigned = td3;
271 /* slot_fill(kg); */ /* will replace it with another */
272 }
273 }
274 #endif
275
276 /*
277 * Change the priority of a thread that is on the run queue.
278 */
279 void
280 adjustrunqueue( struct thread *td, int newpri)
281 {
282 struct ksegrp *kg;
283 struct kse *ke;
284
285 mtx_assert(&sched_lock, MA_OWNED);
286 KASSERT((TD_ON_RUNQ(td)), ("adjustrunqueue: Bad state on run queue"));
287
288 ke = td->td_kse;
289 CTR1(KTR_RUNQ, "adjustrunqueue: td%p", td);
290 /*
291 * If it is not a threaded process, take the shortcut.
292 */
293 if ((td->td_proc->p_flag & P_HADTHREADS) == 0) {
294 /* We only care about the kse in the run queue. */
295 td->td_priority = newpri;
296 if (ke->ke_rqindex != (newpri / RQ_PPQ)) {
297 sched_rem(td);
298 sched_add(td, SRQ_BORING);
299 }
300 return;
301 }
302
303 /* It is a threaded process */
304 kg = td->td_ksegrp;
305 if (ke->ke_state == KES_ONRUNQ) {
306 if (kg->kg_last_assigned == td) {
307 kg->kg_last_assigned =
308 TAILQ_PREV(td, threadqueue, td_runq);
309 }
310 sched_rem(td);
311 }
312 TAILQ_REMOVE(&kg->kg_runq, td, td_runq);
313 kg->kg_runnable--;
314 TD_SET_CAN_RUN(td);
315 td->td_priority = newpri;
316 setrunqueue(td, SRQ_BORING);
317 }
318
319 /*
320 * This function is called when a thread is about to be put on a
321 * ksegrp run queue because it has been made runnable or its
322 * priority has been adjusted and the ksegrp does not have a
323 * free kse slot. It determines if a thread from the same ksegrp
324 * should be preempted. If so, it tries to switch threads
325 * if the thread is on the same cpu or notifies another cpu that
326 * it should switch threads.
327 */
328
329 static void
330 maybe_preempt_in_ksegrp(struct thread *td)
331 #if !defined(SMP)
332 {
333 struct thread *running_thread;
334
335 #ifndef FULL_PREEMPTION
336 int pri;
337 pri = td->td_priority;
338 if (!(pri >= PRI_MIN_ITHD && pri <= PRI_MAX_ITHD))
339 return;
340 #endif
341 mtx_assert(&sched_lock, MA_OWNED);
342 running_thread = curthread;
343
344 if (running_thread->td_ksegrp != td->td_ksegrp)
345 return;
346
347 if (td->td_priority > running_thread->td_priority)
348 return;
349 #ifdef PREEMPTION
350 if (running_thread->td_critnest > 1)
351 running_thread->td_pflags |= TDP_OWEPREEMPT;
352 else
353 mi_switch(SW_INVOL, NULL);
354
355 #else
356 running_thread->td_flags |= TDF_NEEDRESCHED;
357 #endif
358 return;
359 }
360
361 #else /* SMP */
362 {
363 struct thread *running_thread;
364 int worst_pri;
365 struct ksegrp *kg;
366 cpumask_t cpumask,dontuse;
367 struct pcpu *pc;
368 struct pcpu *best_pcpu;
369 struct thread *cputhread;
370
371 #ifndef FULL_PREEMPTION
372 int pri;
373 pri = td->td_priority;
374 if (!(pri >= PRI_MIN_ITHD && pri <= PRI_MAX_ITHD))
375 return;
376 #endif
377
378 mtx_assert(&sched_lock, MA_OWNED);
379
380 running_thread = curthread;
381
382 #if !defined(KSEG_PEEMPT_BEST_CPU)
383 if (running_thread->td_ksegrp != td->td_ksegrp) {
384 #endif
385 kg = td->td_ksegrp;
386
387 /* if someone is ahead of this thread, wait our turn */
388 if (td != TAILQ_FIRST(&kg->kg_runq))
389 return;
390
391 worst_pri = td->td_priority;
392 best_pcpu = NULL;
393 dontuse = stopped_cpus | idle_cpus_mask;
394
395 /*
396 * Find a cpu with the worst priority that runs at thread from
397 * the same ksegrp - if multiple exist give first the last run
398 * cpu and then the current cpu priority
399 */
400
401 SLIST_FOREACH(pc, &cpuhead, pc_allcpu) {
402 cpumask = pc->pc_cpumask;
403 cputhread = pc->pc_curthread;
404
405 if ((cpumask & dontuse) ||
406 cputhread->td_ksegrp != kg)
407 continue;
408
409 if (cputhread->td_priority > worst_pri) {
410 worst_pri = cputhread->td_priority;
411 best_pcpu = pc;
412 continue;
413 }
414
415 if (cputhread->td_priority == worst_pri &&
416 best_pcpu != NULL &&
417 (td->td_lastcpu == pc->pc_cpuid ||
418 (PCPU_GET(cpumask) == cpumask &&
419 td->td_lastcpu != best_pcpu->pc_cpuid)))
420 best_pcpu = pc;
421 }
422
423 /* Check if we need to preempt someone */
424 if (best_pcpu == NULL)
425 return;
426
427 if (PCPU_GET(cpuid) != best_pcpu->pc_cpuid) {
428 best_pcpu->pc_curthread->td_flags |= TDF_NEEDRESCHED;
429 ipi_selected(best_pcpu->pc_cpumask, IPI_AST);
430 return;
431 }
432 #if !defined(KSEG_PEEMPT_BEST_CPU)
433 }
434 #endif
435
436 if (td->td_priority > running_thread->td_priority)
437 return;
438 #ifdef PREEMPTION
439 if (running_thread->td_critnest > 1)
440 running_thread->td_pflags |= TDP_OWEPREEMPT;
441 else
442 mi_switch(SW_INVOL, NULL);
443
444 #else
445 running_thread->td_flags |= TDF_NEEDRESCHED;
446 #endif
447 return;
448 }
449 #endif /* !SMP */
450
451
452 int limitcount;
453 void
454 setrunqueue(struct thread *td, int flags)
455 {
456 struct ksegrp *kg;
457 struct thread *td2;
458 struct thread *tda;
459
460 CTR3(KTR_RUNQ, "setrunqueue: td:%p kg:%p pid:%d",
461 td, td->td_ksegrp, td->td_proc->p_pid);
462 mtx_assert(&sched_lock, MA_OWNED);
463 KASSERT((td->td_inhibitors == 0),
464 ("setrunqueue: trying to run inhibitted thread"));
465 KASSERT((TD_CAN_RUN(td) || TD_IS_RUNNING(td)),
466 ("setrunqueue: bad thread state"));
467 TD_SET_RUNQ(td);
468 kg = td->td_ksegrp;
469 if ((td->td_proc->p_flag & P_HADTHREADS) == 0) {
470 /*
471 * Common path optimisation: Only one of everything
472 * and the KSE is always already attached.
473 * Totally ignore the ksegrp run queue.
474 */
475 if (kg->kg_avail_opennings != 1) {
476 if (limitcount < 1) {
477 limitcount++;
478 printf("pid %d: corrected slot count (%d->1)\n",
479 td->td_proc->p_pid, kg->kg_avail_opennings);
480
481 }
482 kg->kg_avail_opennings = 1;
483 }
484 sched_add(td, flags);
485 return;
486 }
487
488 /*
489 * If the concurrency has reduced, and we would go in the
490 * assigned section, then keep removing entries from the
491 * system run queue, until we are not in that section
492 * or there is room for us to be put in that section.
493 * What we MUST avoid is the case where there are threads of less
494 * priority than the new one scheduled, but it can not
495 * be scheduled itself. That would lead to a non contiguous set
496 * of scheduled threads, and everything would break.
497 */
498 tda = kg->kg_last_assigned;
499 while ((kg->kg_avail_opennings <= 0) &&
500 (tda && (tda->td_priority > td->td_priority))) {
501 /*
502 * None free, but there is one we can commandeer.
503 */
504 CTR2(KTR_RUNQ,
505 "setrunqueue: kg:%p: take slot from td: %p", kg, tda);
506 sched_rem(tda);
507 tda = kg->kg_last_assigned =
508 TAILQ_PREV(tda, threadqueue, td_runq);
509 }
510
511 /*
512 * Add the thread to the ksegrp's run queue at
513 * the appropriate place.
514 */
515 TAILQ_FOREACH(td2, &kg->kg_runq, td_runq) {
516 if (td2->td_priority > td->td_priority) {
517 kg->kg_runnable++;
518 TAILQ_INSERT_BEFORE(td2, td, td_runq);
519 break;
520 }
521 }
522 if (td2 == NULL) {
523 /* We ran off the end of the TAILQ or it was empty. */
524 kg->kg_runnable++;
525 TAILQ_INSERT_TAIL(&kg->kg_runq, td, td_runq);
526 }
527
528 /*
529 * If we have a slot to use, then put the thread on the system
530 * run queue and if needed, readjust the last_assigned pointer.
531 * it may be that we need to schedule something anyhow
532 * even if the availabel slots are -ve so that
533 * all the items < last_assigned are scheduled.
534 */
535 if (kg->kg_avail_opennings > 0) {
536 if (tda == NULL) {
537 /*
538 * No pre-existing last assigned so whoever is first
539 * gets the slot.. (maybe us)
540 */
541 td2 = TAILQ_FIRST(&kg->kg_runq);
542 kg->kg_last_assigned = td2;
543 } else if (tda->td_priority > td->td_priority) {
544 td2 = td;
545 } else {
546 /*
547 * We are past last_assigned, so
548 * give the next slot to whatever is next,
549 * which may or may not be us.
550 */
551 td2 = TAILQ_NEXT(tda, td_runq);
552 kg->kg_last_assigned = td2;
553 }
554 sched_add(td2, flags);
555 } else {
556 CTR3(KTR_RUNQ, "setrunqueue: held: td%p kg%p pid%d",
557 td, td->td_ksegrp, td->td_proc->p_pid);
558 if ((flags & SRQ_YIELDING) == 0)
559 maybe_preempt_in_ksegrp(td);
560 }
561 }
562
563 /*
564 * Kernel thread preemption implementation. Critical sections mark
565 * regions of code in which preemptions are not allowed.
566 */
567 void
568 critical_enter(void)
569 {
570 struct thread *td;
571
572 td = curthread;
573 if (td->td_critnest == 0)
574 cpu_critical_enter(td);
575 td->td_critnest++;
576 }
577
578 void
579 critical_exit(void)
580 {
581 struct thread *td;
582
583 td = curthread;
584 KASSERT(td->td_critnest != 0,
585 ("critical_exit: td_critnest == 0"));
586 if (td->td_critnest == 1) {
587 if (td->td_pflags & TDP_WAKEPROC0) {
588 td->td_pflags &= ~TDP_WAKEPROC0;
589 wakeup(&proc0);
590 }
591 #ifdef PREEMPTION
592 mtx_assert(&sched_lock, MA_NOTOWNED);
593 if (td->td_pflags & TDP_OWEPREEMPT) {
594 mtx_lock_spin(&sched_lock);
595 mi_switch(SW_INVOL, NULL);
596 mtx_unlock_spin(&sched_lock);
597 }
598 #endif
599 td->td_critnest = 0;
600 cpu_critical_exit(td);
601 } else {
602 td->td_critnest--;
603 }
604 }
605
606 /*
607 * This function is called when a thread is about to be put on run queue
608 * because it has been made runnable or its priority has been adjusted. It
609 * determines if the new thread should be immediately preempted to. If so,
610 * it switches to it and eventually returns true. If not, it returns false
611 * so that the caller may place the thread on an appropriate run queue.
612 */
613 int
614 maybe_preempt(struct thread *td)
615 {
616 #ifdef PREEMPTION
617 struct thread *ctd;
618 int cpri, pri;
619 #endif
620
621 mtx_assert(&sched_lock, MA_OWNED);
622 #ifdef PREEMPTION
623 /*
624 * The new thread should not preempt the current thread if any of the
625 * following conditions are true:
626 *
627 * - The current thread has a higher (numerically lower) or
628 * equivalent priority. Note that this prevents curthread from
629 * trying to preempt to itself.
630 * - It is too early in the boot for context switches (cold is set).
631 * - The current thread has an inhibitor set or is in the process of
632 * exiting. In this case, the current thread is about to switch
633 * out anyways, so there's no point in preempting. If we did,
634 * the current thread would not be properly resumed as well, so
635 * just avoid that whole landmine.
636 * - If the new thread's priority is not a realtime priority and
637 * the current thread's priority is not an idle priority and
638 * FULL_PREEMPTION is disabled.
639 *
640 * If all of these conditions are false, but the current thread is in
641 * a nested critical section, then we have to defer the preemption
642 * until we exit the critical section. Otherwise, switch immediately
643 * to the new thread.
644 */
645 ctd = curthread;
646 KASSERT ((ctd->td_kse != NULL && ctd->td_kse->ke_thread == ctd),
647 ("thread has no (or wrong) sched-private part."));
648 KASSERT((td->td_inhibitors == 0),
649 ("maybe_preempt: trying to run inhibitted thread"));
650 pri = td->td_priority;
651 cpri = ctd->td_priority;
652 if (pri >= cpri || cold /* || dumping */ || TD_IS_INHIBITED(ctd) ||
653 td->td_kse->ke_state != KES_THREAD)
654 return (0);
655 #ifndef FULL_PREEMPTION
656 if (!(pri >= PRI_MIN_ITHD && pri <= PRI_MAX_ITHD) &&
657 !(cpri >= PRI_MIN_IDLE))
658 return (0);
659 #endif
660 if (ctd->td_critnest > 1) {
661 CTR1(KTR_PROC, "maybe_preempt: in critical section %d",
662 ctd->td_critnest);
663 ctd->td_pflags |= TDP_OWEPREEMPT;
664 return (0);
665 }
666
667 /*
668 * Thread is runnable but not yet put on system run queue.
669 */
670 MPASS(TD_ON_RUNQ(td));
671 MPASS(td->td_sched->ke_state != KES_ONRUNQ);
672 if (td->td_proc->p_flag & P_HADTHREADS) {
673 /*
674 * If this is a threaded process we actually ARE on the
675 * ksegrp run queue so take it off that first.
676 * Also undo any damage done to the last_assigned pointer.
677 * XXX Fix setrunqueue so this isn't needed
678 */
679 struct ksegrp *kg;
680
681 kg = td->td_ksegrp;
682 if (kg->kg_last_assigned == td)
683 kg->kg_last_assigned =
684 TAILQ_PREV(td, threadqueue, td_runq);
685 TAILQ_REMOVE(&kg->kg_runq, td, td_runq);
686 }
687
688 TD_SET_RUNNING(td);
689 CTR3(KTR_PROC, "preempting to thread %p (pid %d, %s)\n", td,
690 td->td_proc->p_pid, td->td_proc->p_comm);
691 mi_switch(SW_INVOL|SW_PREEMPT, td);
692 return (1);
693 #else
694 return (0);
695 #endif
696 }
697
698 #if 0
699 #ifndef PREEMPTION
700 /* XXX: There should be a non-static version of this. */
701 static void
702 printf_caddr_t(void *data)
703 {
704 printf("%s", (char *)data);
705 }
706 static char preempt_warning[] =
707 "WARNING: Kernel preemption is disabled, expect reduced performance.\n";
708 SYSINIT(preempt_warning, SI_SUB_COPYRIGHT, SI_ORDER_ANY, printf_caddr_t,
709 preempt_warning)
710 #endif
711 #endif
712
713 /************************************************************************
714 * SYSTEM RUN QUEUE manipulations and tests *
715 ************************************************************************/
716 /*
717 * Initialize a run structure.
718 */
719 void
720 runq_init(struct runq *rq)
721 {
722 int i;
723
724 bzero(rq, sizeof *rq);
725 for (i = 0; i < RQ_NQS; i++)
726 TAILQ_INIT(&rq->rq_queues[i]);
727 }
728
729 /*
730 * Clear the status bit of the queue corresponding to priority level pri,
731 * indicating that it is empty.
732 */
733 static __inline void
734 runq_clrbit(struct runq *rq, int pri)
735 {
736 struct rqbits *rqb;
737
738 rqb = &rq->rq_status;
739 CTR4(KTR_RUNQ, "runq_clrbit: bits=%#x %#x bit=%#x word=%d",
740 rqb->rqb_bits[RQB_WORD(pri)],
741 rqb->rqb_bits[RQB_WORD(pri)] & ~RQB_BIT(pri),
742 RQB_BIT(pri), RQB_WORD(pri));
743 rqb->rqb_bits[RQB_WORD(pri)] &= ~RQB_BIT(pri);
744 }
745
746 /*
747 * Find the index of the first non-empty run queue. This is done by
748 * scanning the status bits, a set bit indicates a non-empty queue.
749 */
750 static __inline int
751 runq_findbit(struct runq *rq)
752 {
753 struct rqbits *rqb;
754 int pri;
755 int i;
756
757 rqb = &rq->rq_status;
758 for (i = 0; i < RQB_LEN; i++)
759 if (rqb->rqb_bits[i]) {
760 pri = RQB_FFS(rqb->rqb_bits[i]) + (i << RQB_L2BPW);
761 CTR3(KTR_RUNQ, "runq_findbit: bits=%#x i=%d pri=%d",
762 rqb->rqb_bits[i], i, pri);
763 return (pri);
764 }
765
766 return (-1);
767 }
768
769 /*
770 * Set the status bit of the queue corresponding to priority level pri,
771 * indicating that it is non-empty.
772 */
773 static __inline void
774 runq_setbit(struct runq *rq, int pri)
775 {
776 struct rqbits *rqb;
777
778 rqb = &rq->rq_status;
779 CTR4(KTR_RUNQ, "runq_setbit: bits=%#x %#x bit=%#x word=%d",
780 rqb->rqb_bits[RQB_WORD(pri)],
781 rqb->rqb_bits[RQB_WORD(pri)] | RQB_BIT(pri),
782 RQB_BIT(pri), RQB_WORD(pri));
783 rqb->rqb_bits[RQB_WORD(pri)] |= RQB_BIT(pri);
784 }
785
786 /*
787 * Add the KSE to the queue specified by its priority, and set the
788 * corresponding status bit.
789 */
790 void
791 runq_add(struct runq *rq, struct kse *ke, int flags)
792 {
793 struct rqhead *rqh;
794 int pri;
795
796 pri = ke->ke_thread->td_priority / RQ_PPQ;
797 ke->ke_rqindex = pri;
798 runq_setbit(rq, pri);
799 rqh = &rq->rq_queues[pri];
800 CTR5(KTR_RUNQ, "runq_add: td=%p ke=%p pri=%d %d rqh=%p",
801 ke->ke_thread, ke, ke->ke_thread->td_priority, pri, rqh);
802 if (flags & SRQ_PREEMPTED) {
803 TAILQ_INSERT_HEAD(rqh, ke, ke_procq);
804 } else {
805 TAILQ_INSERT_TAIL(rqh, ke, ke_procq);
806 }
807 }
808
809 /*
810 * Return true if there are runnable processes of any priority on the run
811 * queue, false otherwise. Has no side effects, does not modify the run
812 * queue structure.
813 */
814 int
815 runq_check(struct runq *rq)
816 {
817 struct rqbits *rqb;
818 int i;
819
820 rqb = &rq->rq_status;
821 for (i = 0; i < RQB_LEN; i++)
822 if (rqb->rqb_bits[i]) {
823 CTR2(KTR_RUNQ, "runq_check: bits=%#x i=%d",
824 rqb->rqb_bits[i], i);
825 return (1);
826 }
827 CTR0(KTR_RUNQ, "runq_check: empty");
828
829 return (0);
830 }
831
832 #if defined(SMP) && defined(SCHED_4BSD)
833 int runq_fuzz = 1;
834 SYSCTL_INT(_kern_sched, OID_AUTO, runq_fuzz, CTLFLAG_RW, &runq_fuzz, 0, "");
835 #endif
836
837 /*
838 * Find the highest priority process on the run queue.
839 */
840 struct kse *
841 runq_choose(struct runq *rq)
842 {
843 struct rqhead *rqh;
844 struct kse *ke;
845 int pri;
846
847 mtx_assert(&sched_lock, MA_OWNED);
848 while ((pri = runq_findbit(rq)) != -1) {
849 rqh = &rq->rq_queues[pri];
850 #if defined(SMP) && defined(SCHED_4BSD)
851 /* fuzz == 1 is normal.. 0 or less are ignored */
852 if (runq_fuzz > 1) {
853 /*
854 * In the first couple of entries, check if
855 * there is one for our CPU as a preference.
856 */
857 int count = runq_fuzz;
858 int cpu = PCPU_GET(cpuid);
859 struct kse *ke2;
860 ke2 = ke = TAILQ_FIRST(rqh);
861
862 while (count-- && ke2) {
863 if (ke->ke_thread->td_lastcpu == cpu) {
864 ke = ke2;
865 break;
866 }
867 ke2 = TAILQ_NEXT(ke2, ke_procq);
868 }
869 } else
870 #endif
871 ke = TAILQ_FIRST(rqh);
872 KASSERT(ke != NULL, ("runq_choose: no proc on busy queue"));
873 CTR3(KTR_RUNQ,
874 "runq_choose: pri=%d kse=%p rqh=%p", pri, ke, rqh);
875 return (ke);
876 }
877 CTR1(KTR_RUNQ, "runq_choose: idleproc pri=%d", pri);
878
879 return (NULL);
880 }
881
882 /*
883 * Remove the KSE from the queue specified by its priority, and clear the
884 * corresponding status bit if the queue becomes empty.
885 * Caller must set ke->ke_state afterwards.
886 */
887 void
888 runq_remove(struct runq *rq, struct kse *ke)
889 {
890 struct rqhead *rqh;
891 int pri;
892
893 KASSERT(ke->ke_proc->p_sflag & PS_INMEM,
894 ("runq_remove: process swapped out"));
895 pri = ke->ke_rqindex;
896 rqh = &rq->rq_queues[pri];
897 CTR5(KTR_RUNQ, "runq_remove: td=%p, ke=%p pri=%d %d rqh=%p",
898 ke->ke_thread, ke, ke->ke_thread->td_priority, pri, rqh);
899 KASSERT(ke != NULL, ("runq_remove: no proc on busy queue"));
900 TAILQ_REMOVE(rqh, ke, ke_procq);
901 if (TAILQ_EMPTY(rqh)) {
902 CTR0(KTR_RUNQ, "runq_remove: empty");
903 runq_clrbit(rq, pri);
904 }
905 }
906
907 /****** functions that are temporarily here ***********/
908 #include <vm/uma.h>
909 #define RANGEOF(type, start, end) (offsetof(type, end) - offsetof(type, start))
910 extern struct mtx kse_zombie_lock;
911
912 /*
913 * Allocate scheduler specific per-process resources.
914 * The thread and ksegrp have already been linked in.
915 * In this case just set the default concurrency value.
916 *
917 * Called from:
918 * proc_init() (UMA init method)
919 */
920 void
921 sched_newproc(struct proc *p, struct ksegrp *kg, struct thread *td)
922 {
923
924 /* This can go in sched_fork */
925 sched_init_concurrency(kg);
926 }
927
928 /*
929 * Called by the uma process fini routine..
930 * undo anything we may have done in the uma_init method.
931 * Panic if it's not all 1:1:1:1
932 * Called from:
933 * proc_fini() (UMA method)
934 */
935 void
936 sched_destroyproc(struct proc *p)
937 {
938
939 /* this function slated for destruction */
940 KASSERT((p->p_numthreads == 1), ("Cached proc with > 1 thread "));
941 KASSERT((p->p_numksegrps == 1), ("Cached proc with > 1 ksegrp "));
942 }
943
944 #define RANGEOF(type, start, end) (offsetof(type, end) - offsetof(type, start))
945 /*
946 * thread is being either created or recycled.
947 * Fix up the per-scheduler resources associated with it.
948 * Called from:
949 * sched_fork_thread()
950 * thread_dtor() (*may go away)
951 * thread_init() (*may go away)
952 */
953 void
954 sched_newthread(struct thread *td)
955 {
956 struct td_sched *ke;
957
958 ke = (struct td_sched *) (td + 1);
959 bzero(ke, sizeof(*ke));
960 td->td_sched = ke;
961 ke->ke_thread = td;
962 ke->ke_oncpu = NOCPU;
963 ke->ke_state = KES_THREAD;
964 }
965
966 /*
967 * Set up an initial concurrency of 1
968 * and set the given thread (if given) to be using that
969 * concurrency slot.
970 * May be used "offline"..before the ksegrp is attached to the world
971 * and thus wouldn't need schedlock in that case.
972 * Called from:
973 * thr_create()
974 * proc_init() (UMA) via sched_newproc()
975 */
976 void
977 sched_init_concurrency(struct ksegrp *kg)
978 {
979
980 CTR1(KTR_RUNQ,"kg %p init slots and concurrency to 1", kg);
981 kg->kg_concurrency = 1;
982 kg->kg_avail_opennings = 1;
983 }
984
985 /*
986 * Change the concurrency of an existing ksegrp to N
987 * Called from:
988 * kse_create()
989 * kse_exit()
990 * thread_exit()
991 * thread_single()
992 */
993 void
994 sched_set_concurrency(struct ksegrp *kg, int concurrency)
995 {
996
997 CTR4(KTR_RUNQ,"kg %p set concurrency to %d, slots %d -> %d",
998 kg,
999 concurrency,
1000 kg->kg_avail_opennings,
1001 kg->kg_avail_opennings + (concurrency - kg->kg_concurrency));
1002 kg->kg_avail_opennings += (concurrency - kg->kg_concurrency);
1003 kg->kg_concurrency = concurrency;
1004 }
1005
1006 /*
1007 * Called from thread_exit() for all exiting thread
1008 *
1009 * Not to be confused with sched_exit_thread()
1010 * that is only called from thread_exit() for threads exiting
1011 * without the rest of the process exiting because it is also called from
1012 * sched_exit() and we wouldn't want to call it twice.
1013 * XXX This can probably be fixed.
1014 */
1015 void
1016 sched_thread_exit(struct thread *td)
1017 {
1018
1019 SLOT_RELEASE(td->td_ksegrp);
1020 slot_fill(td->td_ksegrp);
1021 }
1022
1023 #endif /* KERN_SWITCH_INCLUDE */
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