xref: /freebsd/sys/kern/kern_intr.c (revision 74bf4e164ba5851606a27d4feff27717452583e5)
1 /*
2  * Copyright (c) 1997, Stefan Esser <se@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 unmodified, this list of conditions, and the following
10  *    disclaimer.
11  * 2. Redistributions in binary form must reproduce the above copyright
12  *    notice, this list of conditions and the following disclaimer in the
13  *    documentation and/or other materials provided with the distribution.
14  *
15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
16  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
19  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25  */
26 
27 #include <sys/cdefs.h>
28 __FBSDID("$FreeBSD$");
29 
30 #include "opt_ddb.h"
31 
32 #include <sys/param.h>
33 #include <sys/bus.h>
34 #include <sys/conf.h>
35 #include <sys/rtprio.h>
36 #include <sys/systm.h>
37 #include <sys/interrupt.h>
38 #include <sys/kernel.h>
39 #include <sys/kthread.h>
40 #include <sys/ktr.h>
41 #include <sys/limits.h>
42 #include <sys/lock.h>
43 #include <sys/malloc.h>
44 #include <sys/mutex.h>
45 #include <sys/proc.h>
46 #include <sys/random.h>
47 #include <sys/resourcevar.h>
48 #include <sys/sysctl.h>
49 #include <sys/unistd.h>
50 #include <sys/vmmeter.h>
51 #include <machine/atomic.h>
52 #include <machine/cpu.h>
53 #include <machine/md_var.h>
54 #include <machine/stdarg.h>
55 #ifdef DDB
56 #include <ddb/ddb.h>
57 #include <ddb/db_sym.h>
58 #endif
59 
60 struct	int_entropy {
61 	struct	proc *proc;
62 	uintptr_t vector;
63 };
64 
65 struct	ithd *clk_ithd;
66 struct	ithd *tty_ithd;
67 void	*softclock_ih;
68 void	*vm_ih;
69 
70 static MALLOC_DEFINE(M_ITHREAD, "ithread", "Interrupt Threads");
71 
72 static int intr_storm_threshold = 500;
73 TUNABLE_INT("hw.intr_storm_threshold", &intr_storm_threshold);
74 SYSCTL_INT(_hw, OID_AUTO, intr_storm_threshold, CTLFLAG_RW,
75     &intr_storm_threshold, 0,
76     "Number of consecutive interrupts before storm protection is enabled");
77 
78 static void	ithread_loop(void *);
79 static void	ithread_update(struct ithd *);
80 static void	start_softintr(void *);
81 
82 u_char
83 ithread_priority(enum intr_type flags)
84 {
85 	u_char pri;
86 
87 	flags &= (INTR_TYPE_TTY | INTR_TYPE_BIO | INTR_TYPE_NET |
88 	    INTR_TYPE_CAM | INTR_TYPE_MISC | INTR_TYPE_CLK | INTR_TYPE_AV);
89 	switch (flags) {
90 	case INTR_TYPE_TTY:
91 		pri = PI_TTYLOW;
92 		break;
93 	case INTR_TYPE_BIO:
94 		/*
95 		 * XXX We need to refine this.  BSD/OS distinguishes
96 		 * between tape and disk priorities.
97 		 */
98 		pri = PI_DISK;
99 		break;
100 	case INTR_TYPE_NET:
101 		pri = PI_NET;
102 		break;
103 	case INTR_TYPE_CAM:
104 		pri = PI_DISK;          /* XXX or PI_CAM? */
105 		break;
106 	case INTR_TYPE_AV:		/* Audio/video */
107 		pri = PI_AV;
108 		break;
109 	case INTR_TYPE_CLK:
110 		pri = PI_REALTIME;
111 		break;
112 	case INTR_TYPE_MISC:
113 		pri = PI_DULL;          /* don't care */
114 		break;
115 	default:
116 		/* We didn't specify an interrupt level. */
117 		panic("ithread_priority: no interrupt type in flags");
118 	}
119 
120 	return pri;
121 }
122 
123 /*
124  * Regenerate the name (p_comm) and priority for a threaded interrupt thread.
125  */
126 static void
127 ithread_update(struct ithd *ithd)
128 {
129 	struct intrhand *ih;
130 	struct thread *td;
131 	struct proc *p;
132 	int entropy;
133 
134 	mtx_assert(&ithd->it_lock, MA_OWNED);
135 	td = ithd->it_td;
136 	if (td == NULL)
137 		return;
138 	p = td->td_proc;
139 
140 	strlcpy(p->p_comm, ithd->it_name, sizeof(p->p_comm));
141 
142 	ih = TAILQ_FIRST(&ithd->it_handlers);
143 	if (ih == NULL) {
144 		mtx_lock_spin(&sched_lock);
145 		td->td_priority = PRI_MAX_ITHD;
146 		td->td_base_pri = PRI_MAX_ITHD;
147 		mtx_unlock_spin(&sched_lock);
148 		ithd->it_flags &= ~IT_ENTROPY;
149 		return;
150 	}
151 	entropy = 0;
152 	mtx_lock_spin(&sched_lock);
153 	td->td_priority = ih->ih_pri;
154 	td->td_base_pri = ih->ih_pri;
155 	mtx_unlock_spin(&sched_lock);
156 	TAILQ_FOREACH(ih, &ithd->it_handlers, ih_next) {
157 		if (strlen(p->p_comm) + strlen(ih->ih_name) + 1 <
158 		    sizeof(p->p_comm)) {
159 			strcat(p->p_comm, " ");
160 			strcat(p->p_comm, ih->ih_name);
161 		} else if (strlen(p->p_comm) + 1 == sizeof(p->p_comm)) {
162 			if (p->p_comm[sizeof(p->p_comm) - 2] == '+')
163 				p->p_comm[sizeof(p->p_comm) - 2] = '*';
164 			else
165 				p->p_comm[sizeof(p->p_comm) - 2] = '+';
166 		} else
167 			strcat(p->p_comm, "+");
168 		if (ih->ih_flags & IH_ENTROPY)
169 			entropy++;
170 	}
171 	if (entropy)
172 		ithd->it_flags |= IT_ENTROPY;
173 	else
174 		ithd->it_flags &= ~IT_ENTROPY;
175 	CTR2(KTR_INTR, "%s: updated %s", __func__, p->p_comm);
176 }
177 
178 int
179 ithread_create(struct ithd **ithread, uintptr_t vector, int flags,
180     void (*disable)(uintptr_t), void (*enable)(uintptr_t), const char *fmt, ...)
181 {
182 	struct ithd *ithd;
183 	struct thread *td;
184 	struct proc *p;
185 	int error;
186 	va_list ap;
187 
188 	/* The only valid flag during creation is IT_SOFT. */
189 	if ((flags & ~IT_SOFT) != 0)
190 		return (EINVAL);
191 
192 	ithd = malloc(sizeof(struct ithd), M_ITHREAD, M_WAITOK | M_ZERO);
193 	ithd->it_vector = vector;
194 	ithd->it_disable = disable;
195 	ithd->it_enable = enable;
196 	ithd->it_flags = flags;
197 	TAILQ_INIT(&ithd->it_handlers);
198 	mtx_init(&ithd->it_lock, "ithread", NULL, MTX_DEF);
199 
200 	va_start(ap, fmt);
201 	vsnprintf(ithd->it_name, sizeof(ithd->it_name), fmt, ap);
202 	va_end(ap);
203 
204 	error = kthread_create(ithread_loop, ithd, &p, RFSTOPPED | RFHIGHPID,
205 	    0, "%s", ithd->it_name);
206 	if (error) {
207 		mtx_destroy(&ithd->it_lock);
208 		free(ithd, M_ITHREAD);
209 		return (error);
210 	}
211 	td = FIRST_THREAD_IN_PROC(p);	/* XXXKSE */
212 	mtx_lock_spin(&sched_lock);
213 	td->td_ksegrp->kg_pri_class = PRI_ITHD;
214 	td->td_priority = PRI_MAX_ITHD;
215 	TD_SET_IWAIT(td);
216 	mtx_unlock_spin(&sched_lock);
217 	ithd->it_td = td;
218 	td->td_ithd = ithd;
219 	if (ithread != NULL)
220 		*ithread = ithd;
221 	CTR2(KTR_INTR, "%s: created %s", __func__, ithd->it_name);
222 	return (0);
223 }
224 
225 int
226 ithread_destroy(struct ithd *ithread)
227 {
228 
229 	struct thread *td;
230 	if (ithread == NULL)
231 		return (EINVAL);
232 
233 	td = ithread->it_td;
234 	mtx_lock(&ithread->it_lock);
235 	if (!TAILQ_EMPTY(&ithread->it_handlers)) {
236 		mtx_unlock(&ithread->it_lock);
237 		return (EINVAL);
238 	}
239 	ithread->it_flags |= IT_DEAD;
240 	mtx_lock_spin(&sched_lock);
241 	if (TD_AWAITING_INTR(td)) {
242 		TD_CLR_IWAIT(td);
243 		setrunqueue(td);
244 	}
245 	mtx_unlock_spin(&sched_lock);
246 	mtx_unlock(&ithread->it_lock);
247 	CTR2(KTR_INTR, "%s: killing %s", __func__, ithread->it_name);
248 	return (0);
249 }
250 
251 int
252 ithread_add_handler(struct ithd* ithread, const char *name,
253     driver_intr_t handler, void *arg, u_char pri, enum intr_type flags,
254     void **cookiep)
255 {
256 	struct intrhand *ih, *temp_ih;
257 
258 	if (ithread == NULL || name == NULL || handler == NULL)
259 		return (EINVAL);
260 
261 	ih = malloc(sizeof(struct intrhand), M_ITHREAD, M_WAITOK | M_ZERO);
262 	ih->ih_handler = handler;
263 	ih->ih_argument = arg;
264 	ih->ih_name = name;
265 	ih->ih_ithread = ithread;
266 	ih->ih_pri = pri;
267 	if (flags & INTR_FAST)
268 		ih->ih_flags = IH_FAST;
269 	else if (flags & INTR_EXCL)
270 		ih->ih_flags = IH_EXCLUSIVE;
271 	if (flags & INTR_MPSAFE)
272 		ih->ih_flags |= IH_MPSAFE;
273 	if (flags & INTR_ENTROPY)
274 		ih->ih_flags |= IH_ENTROPY;
275 
276 	mtx_lock(&ithread->it_lock);
277 	if ((flags & INTR_EXCL) != 0 && !TAILQ_EMPTY(&ithread->it_handlers))
278 		goto fail;
279 	if (!TAILQ_EMPTY(&ithread->it_handlers)) {
280 		temp_ih = TAILQ_FIRST(&ithread->it_handlers);
281 		if (temp_ih->ih_flags & IH_EXCLUSIVE)
282 			goto fail;
283 		if ((ih->ih_flags & IH_FAST) && !(temp_ih->ih_flags & IH_FAST))
284 			goto fail;
285 		if (!(ih->ih_flags & IH_FAST) && (temp_ih->ih_flags & IH_FAST))
286 			goto fail;
287 	}
288 
289 	TAILQ_FOREACH(temp_ih, &ithread->it_handlers, ih_next)
290 	    if (temp_ih->ih_pri > ih->ih_pri)
291 		    break;
292 	if (temp_ih == NULL)
293 		TAILQ_INSERT_TAIL(&ithread->it_handlers, ih, ih_next);
294 	else
295 		TAILQ_INSERT_BEFORE(temp_ih, ih, ih_next);
296 	ithread_update(ithread);
297 	mtx_unlock(&ithread->it_lock);
298 
299 	if (cookiep != NULL)
300 		*cookiep = ih;
301 	CTR3(KTR_INTR, "%s: added %s to %s", __func__, ih->ih_name,
302 	    ithread->it_name);
303 	return (0);
304 
305 fail:
306 	mtx_unlock(&ithread->it_lock);
307 	free(ih, M_ITHREAD);
308 	return (EINVAL);
309 }
310 
311 int
312 ithread_remove_handler(void *cookie)
313 {
314 	struct intrhand *handler = (struct intrhand *)cookie;
315 	struct ithd *ithread;
316 #ifdef INVARIANTS
317 	struct intrhand *ih;
318 #endif
319 
320 	if (handler == NULL)
321 		return (EINVAL);
322 	ithread = handler->ih_ithread;
323 	KASSERT(ithread != NULL,
324 	    ("interrupt handler \"%s\" has a NULL interrupt thread",
325 		handler->ih_name));
326 	CTR3(KTR_INTR, "%s: removing %s from %s", __func__, handler->ih_name,
327 	    ithread->it_name);
328 	mtx_lock(&ithread->it_lock);
329 #ifdef INVARIANTS
330 	TAILQ_FOREACH(ih, &ithread->it_handlers, ih_next)
331 		if (ih == handler)
332 			goto ok;
333 	mtx_unlock(&ithread->it_lock);
334 	panic("interrupt handler \"%s\" not found in interrupt thread \"%s\"",
335 	    ih->ih_name, ithread->it_name);
336 ok:
337 #endif
338 	/*
339 	 * If the interrupt thread is already running, then just mark this
340 	 * handler as being dead and let the ithread do the actual removal.
341 	 *
342 	 * During a cold boot while cold is set, msleep() does not sleep,
343 	 * so we have to remove the handler here rather than letting the
344 	 * thread do it.
345 	 */
346 	mtx_lock_spin(&sched_lock);
347 	if (!TD_AWAITING_INTR(ithread->it_td) && !cold) {
348 		handler->ih_flags |= IH_DEAD;
349 
350 		/*
351 		 * Ensure that the thread will process the handler list
352 		 * again and remove this handler if it has already passed
353 		 * it on the list.
354 		 */
355 		ithread->it_need = 1;
356 	} else
357 		TAILQ_REMOVE(&ithread->it_handlers, handler, ih_next);
358 	mtx_unlock_spin(&sched_lock);
359 	if ((handler->ih_flags & IH_DEAD) != 0)
360 		msleep(handler, &ithread->it_lock, PUSER, "itrmh", 0);
361 	ithread_update(ithread);
362 	mtx_unlock(&ithread->it_lock);
363 	free(handler, M_ITHREAD);
364 	return (0);
365 }
366 
367 int
368 ithread_schedule(struct ithd *ithread)
369 {
370 	struct int_entropy entropy;
371 	struct thread *td;
372 	struct thread *ctd;
373 	struct proc *p;
374 
375 	/*
376 	 * If no ithread or no handlers, then we have a stray interrupt.
377 	 */
378 	if ((ithread == NULL) || TAILQ_EMPTY(&ithread->it_handlers))
379 		return (EINVAL);
380 
381 	ctd = curthread;
382 	td = ithread->it_td;
383 	p = td->td_proc;
384 	/*
385 	 * If any of the handlers for this ithread claim to be good
386 	 * sources of entropy, then gather some.
387 	 */
388 	if (harvest.interrupt && ithread->it_flags & IT_ENTROPY) {
389 		CTR3(KTR_INTR, "%s: pid %d (%s) gathering entropy", __func__,
390 		    p->p_pid, p->p_comm);
391 		entropy.vector = ithread->it_vector;
392 		entropy.proc = ctd->td_proc;
393 		random_harvest(&entropy, sizeof(entropy), 2, 0,
394 		    RANDOM_INTERRUPT);
395 	}
396 
397 	KASSERT(p != NULL, ("ithread %s has no process", ithread->it_name));
398 	CTR4(KTR_INTR, "%s: pid %d: (%s) need = %d",
399 	    __func__, p->p_pid, p->p_comm, ithread->it_need);
400 
401 	/*
402 	 * Set it_need to tell the thread to keep running if it is already
403 	 * running.  Then, grab sched_lock and see if we actually need to
404 	 * put this thread on the runqueue.
405 	 */
406 	ithread->it_need = 1;
407 	mtx_lock_spin(&sched_lock);
408 	if (TD_AWAITING_INTR(td)) {
409 		CTR2(KTR_INTR, "%s: setrunqueue %d", __func__, p->p_pid);
410 		TD_CLR_IWAIT(td);
411 		setrunqueue(td);
412 	} else {
413 		CTR4(KTR_INTR, "%s: pid %d: it_need %d, state %d",
414 		    __func__, p->p_pid, ithread->it_need, td->td_state);
415 	}
416 	mtx_unlock_spin(&sched_lock);
417 
418 	return (0);
419 }
420 
421 int
422 swi_add(struct ithd **ithdp, const char *name, driver_intr_t handler,
423 	    void *arg, int pri, enum intr_type flags, void **cookiep)
424 {
425 	struct ithd *ithd;
426 	int error;
427 
428 	if (flags & (INTR_FAST | INTR_ENTROPY))
429 		return (EINVAL);
430 
431 	ithd = (ithdp != NULL) ? *ithdp : NULL;
432 
433 	if (ithd != NULL) {
434 		if ((ithd->it_flags & IT_SOFT) == 0)
435 			return(EINVAL);
436 	} else {
437 		error = ithread_create(&ithd, pri, IT_SOFT, NULL, NULL,
438 		    "swi%d:", pri);
439 		if (error)
440 			return (error);
441 
442 		if (ithdp != NULL)
443 			*ithdp = ithd;
444 	}
445 	return (ithread_add_handler(ithd, name, handler, arg,
446 		    (pri * RQ_PPQ) + PI_SOFT, flags, cookiep));
447 }
448 
449 
450 /*
451  * Schedule a heavyweight software interrupt process.
452  */
453 void
454 swi_sched(void *cookie, int flags)
455 {
456 	struct intrhand *ih = (struct intrhand *)cookie;
457 	struct ithd *it = ih->ih_ithread;
458 	int error;
459 
460 	atomic_add_int(&cnt.v_intr, 1); /* one more global interrupt */
461 
462 	CTR3(KTR_INTR, "swi_sched pid %d(%s) need=%d",
463 		it->it_td->td_proc->p_pid, it->it_td->td_proc->p_comm, it->it_need);
464 
465 	/*
466 	 * Set ih_need for this handler so that if the ithread is already
467 	 * running it will execute this handler on the next pass.  Otherwise,
468 	 * it will execute it the next time it runs.
469 	 */
470 	atomic_store_rel_int(&ih->ih_need, 1);
471 	if (!(flags & SWI_DELAY)) {
472 		error = ithread_schedule(it);
473 		KASSERT(error == 0, ("stray software interrupt"));
474 	}
475 }
476 
477 /*
478  * This is the main code for interrupt threads.
479  */
480 static void
481 ithread_loop(void *arg)
482 {
483 	struct ithd *ithd;		/* our thread context */
484 	struct intrhand *ih;		/* and our interrupt handler chain */
485 	struct thread *td;
486 	struct proc *p;
487 	int count, warming, warned;
488 
489 	td = curthread;
490 	p = td->td_proc;
491 	ithd = (struct ithd *)arg;	/* point to myself */
492 	KASSERT(ithd->it_td == td && td->td_ithd == ithd,
493 	    ("%s: ithread and proc linkage out of sync", __func__));
494 	warming = 10 * intr_storm_threshold;
495 	warned = 0;
496 
497 	/*
498 	 * As long as we have interrupts outstanding, go through the
499 	 * list of handlers, giving each one a go at it.
500 	 */
501 	for (;;) {
502 		/*
503 		 * If we are an orphaned thread, then just die.
504 		 */
505 		if (ithd->it_flags & IT_DEAD) {
506 			CTR3(KTR_INTR, "%s: pid %d: (%s) exiting", __func__,
507 			    p->p_pid, p->p_comm);
508 			td->td_ithd = NULL;
509 			mtx_destroy(&ithd->it_lock);
510 			free(ithd, M_ITHREAD);
511 			kthread_exit(0);
512 		}
513 
514 		CTR4(KTR_INTR, "%s: pid %d: (%s) need=%d", __func__,
515 		     p->p_pid, p->p_comm, ithd->it_need);
516 		count = 0;
517 		while (ithd->it_need) {
518 			/*
519 			 * Service interrupts.  If another interrupt
520 			 * arrives while we are running, they will set
521 			 * it_need to denote that we should make
522 			 * another pass.
523 			 */
524 			atomic_store_rel_int(&ithd->it_need, 0);
525 restart:
526 			TAILQ_FOREACH(ih, &ithd->it_handlers, ih_next) {
527 				if (ithd->it_flags & IT_SOFT && !ih->ih_need)
528 					continue;
529 				atomic_store_rel_int(&ih->ih_need, 0);
530 				CTR6(KTR_INTR,
531 				    "%s: pid %d ih=%p: %p(%p) flg=%x", __func__,
532 				    p->p_pid, (void *)ih,
533 				    (void *)ih->ih_handler, ih->ih_argument,
534 				    ih->ih_flags);
535 
536 				if ((ih->ih_flags & IH_DEAD) != 0) {
537 					mtx_lock(&ithd->it_lock);
538 					TAILQ_REMOVE(&ithd->it_handlers, ih,
539 					    ih_next);
540 					wakeup(ih);
541 					mtx_unlock(&ithd->it_lock);
542 					goto restart;
543 				}
544 				if ((ih->ih_flags & IH_MPSAFE) == 0)
545 					mtx_lock(&Giant);
546 				ih->ih_handler(ih->ih_argument);
547 				if ((ih->ih_flags & IH_MPSAFE) == 0)
548 					mtx_unlock(&Giant);
549 			}
550 			if (ithd->it_enable != NULL) {
551 				ithd->it_enable(ithd->it_vector);
552 
553 				/*
554 				 * Storm detection needs a delay here
555 				 * to see slightly delayed interrupts
556 				 * on some machines, but we don't
557 				 * want to always delay, so only delay
558 				 * while warming up.
559 				 *
560 				 * XXXRW: Calling DELAY() in the interrupt
561 				 * path surely needs to be revisited.
562 				 */
563 				if (warming != 0) {
564 					DELAY(1);
565 					--warming;
566 				}
567 			}
568 
569 			/*
570 			 * If we detect an interrupt storm, sleep until
571 			 * the next hardclock tick.  We sleep at the
572 			 * end of the loop instead of at the beginning
573 			 * to ensure that we see slightly delayed
574 			 * interrupts.
575 			 */
576 			if (count >= intr_storm_threshold) {
577 				if (!warned) {
578 					printf(
579 	"Interrupt storm detected on \"%s\"; throttling interrupt source\n",
580 					    p->p_comm);
581 					warned = 1;
582 				}
583 				tsleep(&count, td->td_priority, "istorm", 1);
584 
585 				/*
586 				 * Fudge the count to re-throttle if the
587 				 * interrupt is still active.  Our storm
588 				 * detection is too primitive to detect
589 				 * whether the storm has gone away
590 				 * reliably, even if we were to waste a
591 				 * lot of time spinning for the next
592 				 * intr_storm_threshold interrupts, so
593 				 * we assume that the storm hasn't gone
594 				 * away unless the interrupt repeats
595 				 * less often the hardclock interrupt.
596 				 */
597 				count = INT_MAX - 1;
598 			}
599 			count++;
600 		}
601 		WITNESS_WARN(WARN_PANIC, NULL, "suspending ithread");
602 		mtx_assert(&Giant, MA_NOTOWNED);
603 
604 		/*
605 		 * Processed all our interrupts.  Now get the sched
606 		 * lock.  This may take a while and it_need may get
607 		 * set again, so we have to check it again.
608 		 */
609 		mtx_lock_spin(&sched_lock);
610 		if (!ithd->it_need) {
611 			TD_SET_IWAIT(td);
612 			CTR2(KTR_INTR, "%s: pid %d: done", __func__, p->p_pid);
613 			mi_switch(SW_VOL, NULL);
614 			CTR2(KTR_INTR, "%s: pid %d: resumed", __func__, p->p_pid);
615 		}
616 		mtx_unlock_spin(&sched_lock);
617 	}
618 }
619 
620 #ifdef DDB
621 /*
622  * Dump details about an interrupt handler
623  */
624 static void
625 db_dump_intrhand(struct intrhand *ih)
626 {
627 	int comma;
628 
629 	db_printf("\t%-10s ", ih->ih_name);
630 	switch (ih->ih_pri) {
631 	case PI_REALTIME:
632 		db_printf("CLK ");
633 		break;
634 	case PI_AV:
635 		db_printf("AV  ");
636 		break;
637 	case PI_TTYHIGH:
638 	case PI_TTYLOW:
639 		db_printf("TTY ");
640 		break;
641 	case PI_TAPE:
642 		db_printf("TAPE");
643 		break;
644 	case PI_NET:
645 		db_printf("NET ");
646 		break;
647 	case PI_DISK:
648 	case PI_DISKLOW:
649 		db_printf("DISK");
650 		break;
651 	case PI_DULL:
652 		db_printf("DULL");
653 		break;
654 	default:
655 		if (ih->ih_pri >= PI_SOFT)
656 			db_printf("SWI ");
657 		else
658 			db_printf("%4u", ih->ih_pri);
659 		break;
660 	}
661 	db_printf(" ");
662 	db_printsym((uintptr_t)ih->ih_handler, DB_STGY_PROC);
663 	db_printf("(%p)", ih->ih_argument);
664 	if (ih->ih_need ||
665 	    (ih->ih_flags & (IH_FAST | IH_EXCLUSIVE | IH_ENTROPY | IH_DEAD |
666 	    IH_MPSAFE)) != 0) {
667 		db_printf(" {");
668 		comma = 0;
669 		if (ih->ih_flags & IH_FAST) {
670 			db_printf("FAST");
671 			comma = 1;
672 		}
673 		if (ih->ih_flags & IH_EXCLUSIVE) {
674 			if (comma)
675 				db_printf(", ");
676 			db_printf("EXCL");
677 			comma = 1;
678 		}
679 		if (ih->ih_flags & IH_ENTROPY) {
680 			if (comma)
681 				db_printf(", ");
682 			db_printf("ENTROPY");
683 			comma = 1;
684 		}
685 		if (ih->ih_flags & IH_DEAD) {
686 			if (comma)
687 				db_printf(", ");
688 			db_printf("DEAD");
689 			comma = 1;
690 		}
691 		if (ih->ih_flags & IH_MPSAFE) {
692 			if (comma)
693 				db_printf(", ");
694 			db_printf("MPSAFE");
695 			comma = 1;
696 		}
697 		if (ih->ih_need) {
698 			if (comma)
699 				db_printf(", ");
700 			db_printf("NEED");
701 		}
702 		db_printf("}");
703 	}
704 	db_printf("\n");
705 }
706 
707 /*
708  * Dump details about an ithread
709  */
710 void
711 db_dump_ithread(struct ithd *ithd, int handlers)
712 {
713 	struct proc *p;
714 	struct intrhand *ih;
715 	int comma;
716 
717 	if (ithd->it_td != NULL) {
718 		p = ithd->it_td->td_proc;
719 		db_printf("%s (pid %d)", p->p_comm, p->p_pid);
720 	} else
721 		db_printf("%s: (no thread)", ithd->it_name);
722 	if ((ithd->it_flags & (IT_SOFT | IT_ENTROPY | IT_DEAD)) != 0 ||
723 	    ithd->it_need) {
724 		db_printf(" {");
725 		comma = 0;
726 		if (ithd->it_flags & IT_SOFT) {
727 			db_printf("SOFT");
728 			comma = 1;
729 		}
730 		if (ithd->it_flags & IT_ENTROPY) {
731 			if (comma)
732 				db_printf(", ");
733 			db_printf("ENTROPY");
734 			comma = 1;
735 		}
736 		if (ithd->it_flags & IT_DEAD) {
737 			if (comma)
738 				db_printf(", ");
739 			db_printf("DEAD");
740 			comma = 1;
741 		}
742 		if (ithd->it_need) {
743 			if (comma)
744 				db_printf(", ");
745 			db_printf("NEED");
746 		}
747 		db_printf("}");
748 	}
749 	db_printf("\n");
750 
751 	if (handlers)
752 		TAILQ_FOREACH(ih, &ithd->it_handlers, ih_next)
753 		    db_dump_intrhand(ih);
754 }
755 #endif /* DDB */
756 
757 /*
758  * Start standard software interrupt threads
759  */
760 static void
761 start_softintr(void *dummy)
762 {
763 	struct proc *p;
764 
765 	if (swi_add(&clk_ithd, "clock", softclock, NULL, SWI_CLOCK,
766 		INTR_MPSAFE, &softclock_ih) ||
767 	    swi_add(NULL, "vm", swi_vm, NULL, SWI_VM, INTR_MPSAFE, &vm_ih))
768 		panic("died while creating standard software ithreads");
769 
770 	p = clk_ithd->it_td->td_proc;
771 	PROC_LOCK(p);
772 	p->p_flag |= P_NOLOAD;
773 	PROC_UNLOCK(p);
774 }
775 SYSINIT(start_softintr, SI_SUB_SOFTINTR, SI_ORDER_FIRST, start_softintr, NULL)
776 
777 /*
778  * Sysctls used by systat and others: hw.intrnames and hw.intrcnt.
779  * The data for this machine dependent, and the declarations are in machine
780  * dependent code.  The layout of intrnames and intrcnt however is machine
781  * independent.
782  *
783  * We do not know the length of intrcnt and intrnames at compile time, so
784  * calculate things at run time.
785  */
786 static int
787 sysctl_intrnames(SYSCTL_HANDLER_ARGS)
788 {
789 	return (sysctl_handle_opaque(oidp, intrnames, eintrnames - intrnames,
790 	   req));
791 }
792 
793 SYSCTL_PROC(_hw, OID_AUTO, intrnames, CTLTYPE_OPAQUE | CTLFLAG_RD,
794     NULL, 0, sysctl_intrnames, "", "Interrupt Names");
795 
796 static int
797 sysctl_intrcnt(SYSCTL_HANDLER_ARGS)
798 {
799 	return (sysctl_handle_opaque(oidp, intrcnt,
800 	    (char *)eintrcnt - (char *)intrcnt, req));
801 }
802 
803 SYSCTL_PROC(_hw, OID_AUTO, intrcnt, CTLTYPE_OPAQUE | CTLFLAG_RD,
804     NULL, 0, sysctl_intrcnt, "", "Interrupt Counts");
805 
806 #ifdef DDB
807 /*
808  * DDB command to dump the interrupt statistics.
809  */
810 DB_SHOW_COMMAND(intrcnt, db_show_intrcnt)
811 {
812 	u_long *i;
813 	char *cp;
814 	int quit;
815 
816 	cp = intrnames;
817 	db_setup_paging(db_simple_pager, &quit, DB_LINES_PER_PAGE);
818 	for (i = intrcnt, quit = 0; i != eintrcnt && !quit; i++) {
819 		if (*cp == '\0')
820 			break;
821 		if (*i != 0)
822 			db_printf("%s\t%lu\n", cp, *i);
823 		cp += strlen(cp) + 1;
824 	}
825 }
826 #endif
827