FreeBSD/Linux Kernel Cross Reference
sys/kern/subr_smp.c
1 /*-
2 * Copyright (c) 2001, John Baldwin <jhb@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 * 3. Neither the name of the author nor the names of any co-contributors
14 * may be used to endorse or promote products derived from this software
15 * without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * SUCH DAMAGE.
28 */
29
30 /*
31 * This module holds the global variables and machine independent functions
32 * used for the kernel SMP support.
33 */
34
35 #include <sys/cdefs.h>
36 __FBSDID("$FreeBSD: releng/9.0/sys/kern/subr_smp.c 227889 2011-11-23 15:41:55Z attilio $");
37
38 #include <sys/param.h>
39 #include <sys/systm.h>
40 #include <sys/kernel.h>
41 #include <sys/ktr.h>
42 #include <sys/proc.h>
43 #include <sys/bus.h>
44 #include <sys/lock.h>
45 #include <sys/mutex.h>
46 #include <sys/pcpu.h>
47 #include <sys/smp.h>
48 #include <sys/sysctl.h>
49
50 #include <machine/cpu.h>
51 #include <machine/smp.h>
52
53 #include "opt_sched.h"
54
55 #ifdef SMP
56 volatile cpuset_t stopped_cpus;
57 volatile cpuset_t started_cpus;
58 cpuset_t hlt_cpus_mask;
59 cpuset_t logical_cpus_mask;
60
61 void (*cpustop_restartfunc)(void);
62 #endif
63 /* This is used in modules that need to work in both SMP and UP. */
64 cpuset_t all_cpus;
65
66 int mp_ncpus;
67 /* export this for libkvm consumers. */
68 int mp_maxcpus = MAXCPU;
69
70 volatile int smp_started;
71 u_int mp_maxid;
72
73 SYSCTL_NODE(_kern, OID_AUTO, smp, CTLFLAG_RD|CTLFLAG_CAPRD, NULL, "Kernel SMP");
74
75 SYSCTL_INT(_kern_smp, OID_AUTO, maxid, CTLFLAG_RD|CTLFLAG_CAPRD, &mp_maxid, 0,
76 "Max CPU ID.");
77
78 SYSCTL_INT(_kern_smp, OID_AUTO, maxcpus, CTLFLAG_RD|CTLFLAG_CAPRD, &mp_maxcpus,
79 0, "Max number of CPUs that the system was compiled for.");
80
81 int smp_active = 0; /* are the APs allowed to run? */
82 SYSCTL_INT(_kern_smp, OID_AUTO, active, CTLFLAG_RW, &smp_active, 0,
83 "Number of Auxillary Processors (APs) that were successfully started");
84
85 int smp_disabled = 0; /* has smp been disabled? */
86 SYSCTL_INT(_kern_smp, OID_AUTO, disabled, CTLFLAG_RDTUN|CTLFLAG_CAPRD,
87 &smp_disabled, 0, "SMP has been disabled from the loader");
88 TUNABLE_INT("kern.smp.disabled", &smp_disabled);
89
90 int smp_cpus = 1; /* how many cpu's running */
91 SYSCTL_INT(_kern_smp, OID_AUTO, cpus, CTLFLAG_RD|CTLFLAG_CAPRD, &smp_cpus, 0,
92 "Number of CPUs online");
93
94 int smp_topology = 0; /* Which topology we're using. */
95 SYSCTL_INT(_kern_smp, OID_AUTO, topology, CTLFLAG_RD, &smp_topology, 0,
96 "Topology override setting; 0 is default provided by hardware.");
97 TUNABLE_INT("kern.smp.topology", &smp_topology);
98
99 #ifdef SMP
100 /* Enable forwarding of a signal to a process running on a different CPU */
101 static int forward_signal_enabled = 1;
102 SYSCTL_INT(_kern_smp, OID_AUTO, forward_signal_enabled, CTLFLAG_RW,
103 &forward_signal_enabled, 0,
104 "Forwarding of a signal to a process on a different CPU");
105
106 /* Variables needed for SMP rendezvous. */
107 static volatile int smp_rv_ncpus;
108 static void (*volatile smp_rv_setup_func)(void *arg);
109 static void (*volatile smp_rv_action_func)(void *arg);
110 static void (*volatile smp_rv_teardown_func)(void *arg);
111 static void *volatile smp_rv_func_arg;
112 static volatile int smp_rv_waiters[4];
113
114 /*
115 * Shared mutex to restrict busywaits between smp_rendezvous() and
116 * smp(_targeted)_tlb_shootdown(). A deadlock occurs if both of these
117 * functions trigger at once and cause multiple CPUs to busywait with
118 * interrupts disabled.
119 */
120 struct mtx smp_ipi_mtx;
121
122 /*
123 * Let the MD SMP code initialize mp_maxid very early if it can.
124 */
125 static void
126 mp_setmaxid(void *dummy)
127 {
128 cpu_mp_setmaxid();
129 }
130 SYSINIT(cpu_mp_setmaxid, SI_SUB_TUNABLES, SI_ORDER_FIRST, mp_setmaxid, NULL);
131
132 /*
133 * Call the MD SMP initialization code.
134 */
135 static void
136 mp_start(void *dummy)
137 {
138
139 mtx_init(&smp_ipi_mtx, "smp rendezvous", NULL, MTX_SPIN);
140
141 /* Probe for MP hardware. */
142 if (smp_disabled != 0 || cpu_mp_probe() == 0) {
143 mp_ncpus = 1;
144 CPU_SETOF(PCPU_GET(cpuid), &all_cpus);
145 return;
146 }
147
148 cpu_mp_start();
149 printf("FreeBSD/SMP: Multiprocessor System Detected: %d CPUs\n",
150 mp_ncpus);
151 cpu_mp_announce();
152 }
153 SYSINIT(cpu_mp, SI_SUB_CPU, SI_ORDER_THIRD, mp_start, NULL);
154
155 void
156 forward_signal(struct thread *td)
157 {
158 int id;
159
160 /*
161 * signotify() has already set TDF_ASTPENDING and TDF_NEEDSIGCHECK on
162 * this thread, so all we need to do is poke it if it is currently
163 * executing so that it executes ast().
164 */
165 THREAD_LOCK_ASSERT(td, MA_OWNED);
166 KASSERT(TD_IS_RUNNING(td),
167 ("forward_signal: thread is not TDS_RUNNING"));
168
169 CTR1(KTR_SMP, "forward_signal(%p)", td->td_proc);
170
171 if (!smp_started || cold || panicstr)
172 return;
173 if (!forward_signal_enabled)
174 return;
175
176 /* No need to IPI ourself. */
177 if (td == curthread)
178 return;
179
180 id = td->td_oncpu;
181 if (id == NOCPU)
182 return;
183 ipi_cpu(id, IPI_AST);
184 }
185
186 /*
187 * When called the executing CPU will send an IPI to all other CPUs
188 * requesting that they halt execution.
189 *
190 * Usually (but not necessarily) called with 'other_cpus' as its arg.
191 *
192 * - Signals all CPUs in map to stop.
193 * - Waits for each to stop.
194 *
195 * Returns:
196 * -1: error
197 * 0: NA
198 * 1: ok
199 *
200 */
201 static int
202 generic_stop_cpus(cpuset_t map, u_int type)
203 {
204 #ifdef KTR
205 char cpusetbuf[CPUSETBUFSIZ];
206 #endif
207 static volatile u_int stopping_cpu = NOCPU;
208 int i;
209
210 KASSERT(
211 #if defined(__amd64__)
212 type == IPI_STOP || type == IPI_STOP_HARD || type == IPI_SUSPEND,
213 #else
214 type == IPI_STOP || type == IPI_STOP_HARD,
215 #endif
216 ("%s: invalid stop type", __func__));
217
218 if (!smp_started)
219 return (0);
220
221 CTR2(KTR_SMP, "stop_cpus(%s) with %u type",
222 cpusetobj_strprint(cpusetbuf, &map), type);
223
224 if (stopping_cpu != PCPU_GET(cpuid))
225 while (atomic_cmpset_int(&stopping_cpu, NOCPU,
226 PCPU_GET(cpuid)) == 0)
227 while (stopping_cpu != NOCPU)
228 cpu_spinwait(); /* spin */
229
230 /* send the stop IPI to all CPUs in map */
231 ipi_selected(map, type);
232
233 i = 0;
234 while (!CPU_SUBSET(&stopped_cpus, &map)) {
235 /* spin */
236 cpu_spinwait();
237 i++;
238 if (i == 100000000) {
239 printf("timeout stopping cpus\n");
240 break;
241 }
242 }
243
244 stopping_cpu = NOCPU;
245 return (1);
246 }
247
248 int
249 stop_cpus(cpuset_t map)
250 {
251
252 return (generic_stop_cpus(map, IPI_STOP));
253 }
254
255 int
256 stop_cpus_hard(cpuset_t map)
257 {
258
259 return (generic_stop_cpus(map, IPI_STOP_HARD));
260 }
261
262 #if defined(__amd64__)
263 int
264 suspend_cpus(cpuset_t map)
265 {
266
267 return (generic_stop_cpus(map, IPI_SUSPEND));
268 }
269 #endif
270
271 /*
272 * Called by a CPU to restart stopped CPUs.
273 *
274 * Usually (but not necessarily) called with 'stopped_cpus' as its arg.
275 *
276 * - Signals all CPUs in map to restart.
277 * - Waits for each to restart.
278 *
279 * Returns:
280 * -1: error
281 * 0: NA
282 * 1: ok
283 */
284 int
285 restart_cpus(cpuset_t map)
286 {
287 #ifdef KTR
288 char cpusetbuf[CPUSETBUFSIZ];
289 #endif
290
291 if (!smp_started)
292 return 0;
293
294 CTR1(KTR_SMP, "restart_cpus(%s)", cpusetobj_strprint(cpusetbuf, &map));
295
296 /* signal other cpus to restart */
297 CPU_COPY_STORE_REL(&map, &started_cpus);
298
299 /* wait for each to clear its bit */
300 while (CPU_OVERLAP(&stopped_cpus, &map))
301 cpu_spinwait();
302
303 return 1;
304 }
305
306 /*
307 * All-CPU rendezvous. CPUs are signalled, all execute the setup function
308 * (if specified), rendezvous, execute the action function (if specified),
309 * rendezvous again, execute the teardown function (if specified), and then
310 * resume.
311 *
312 * Note that the supplied external functions _must_ be reentrant and aware
313 * that they are running in parallel and in an unknown lock context.
314 */
315 void
316 smp_rendezvous_action(void)
317 {
318 struct thread *td;
319 void *local_func_arg;
320 void (*local_setup_func)(void*);
321 void (*local_action_func)(void*);
322 void (*local_teardown_func)(void*);
323 #ifdef INVARIANTS
324 int owepreempt;
325 #endif
326
327 /* Ensure we have up-to-date values. */
328 atomic_add_acq_int(&smp_rv_waiters[0], 1);
329 while (smp_rv_waiters[0] < smp_rv_ncpus)
330 cpu_spinwait();
331
332 /* Fetch rendezvous parameters after acquire barrier. */
333 local_func_arg = smp_rv_func_arg;
334 local_setup_func = smp_rv_setup_func;
335 local_action_func = smp_rv_action_func;
336 local_teardown_func = smp_rv_teardown_func;
337
338 /*
339 * Use a nested critical section to prevent any preemptions
340 * from occurring during a rendezvous action routine.
341 * Specifically, if a rendezvous handler is invoked via an IPI
342 * and the interrupted thread was in the critical_exit()
343 * function after setting td_critnest to 0 but before
344 * performing a deferred preemption, this routine can be
345 * invoked with td_critnest set to 0 and td_owepreempt true.
346 * In that case, a critical_exit() during the rendezvous
347 * action would trigger a preemption which is not permitted in
348 * a rendezvous action. To fix this, wrap all of the
349 * rendezvous action handlers in a critical section. We
350 * cannot use a regular critical section however as having
351 * critical_exit() preempt from this routine would also be
352 * problematic (the preemption must not occur before the IPI
353 * has been acknowledged via an EOI). Instead, we
354 * intentionally ignore td_owepreempt when leaving the
355 * critical section. This should be harmless because we do
356 * not permit rendezvous action routines to schedule threads,
357 * and thus td_owepreempt should never transition from 0 to 1
358 * during this routine.
359 */
360 td = curthread;
361 td->td_critnest++;
362 #ifdef INVARIANTS
363 owepreempt = td->td_owepreempt;
364 #endif
365
366 /*
367 * If requested, run a setup function before the main action
368 * function. Ensure all CPUs have completed the setup
369 * function before moving on to the action function.
370 */
371 if (local_setup_func != smp_no_rendevous_barrier) {
372 if (smp_rv_setup_func != NULL)
373 smp_rv_setup_func(smp_rv_func_arg);
374 atomic_add_int(&smp_rv_waiters[1], 1);
375 while (smp_rv_waiters[1] < smp_rv_ncpus)
376 cpu_spinwait();
377 }
378
379 if (local_action_func != NULL)
380 local_action_func(local_func_arg);
381
382 if (local_teardown_func != smp_no_rendevous_barrier) {
383 /*
384 * Signal that the main action has been completed. If a
385 * full exit rendezvous is requested, then all CPUs will
386 * wait here until all CPUs have finished the main action.
387 */
388 atomic_add_int(&smp_rv_waiters[2], 1);
389 while (smp_rv_waiters[2] < smp_rv_ncpus)
390 cpu_spinwait();
391
392 if (local_teardown_func != NULL)
393 local_teardown_func(local_func_arg);
394 }
395
396 /*
397 * Signal that the rendezvous is fully completed by this CPU.
398 * This means that no member of smp_rv_* pseudo-structure will be
399 * accessed by this target CPU after this point; in particular,
400 * memory pointed by smp_rv_func_arg.
401 */
402 atomic_add_int(&smp_rv_waiters[3], 1);
403
404 td->td_critnest--;
405 KASSERT(owepreempt == td->td_owepreempt,
406 ("rendezvous action changed td_owepreempt"));
407 }
408
409 void
410 smp_rendezvous_cpus(cpuset_t map,
411 void (* setup_func)(void *),
412 void (* action_func)(void *),
413 void (* teardown_func)(void *),
414 void *arg)
415 {
416 int curcpumap, i, ncpus = 0;
417
418 /* Look comments in the !SMP case. */
419 if (!smp_started) {
420 spinlock_enter();
421 if (setup_func != NULL)
422 setup_func(arg);
423 if (action_func != NULL)
424 action_func(arg);
425 if (teardown_func != NULL)
426 teardown_func(arg);
427 spinlock_exit();
428 return;
429 }
430
431 CPU_FOREACH(i) {
432 if (CPU_ISSET(i, &map))
433 ncpus++;
434 }
435 if (ncpus == 0)
436 panic("ncpus is 0 with non-zero map");
437
438 mtx_lock_spin(&smp_ipi_mtx);
439
440 /* Pass rendezvous parameters via global variables. */
441 smp_rv_ncpus = ncpus;
442 smp_rv_setup_func = setup_func;
443 smp_rv_action_func = action_func;
444 smp_rv_teardown_func = teardown_func;
445 smp_rv_func_arg = arg;
446 smp_rv_waiters[1] = 0;
447 smp_rv_waiters[2] = 0;
448 smp_rv_waiters[3] = 0;
449 atomic_store_rel_int(&smp_rv_waiters[0], 0);
450
451 /*
452 * Signal other processors, which will enter the IPI with
453 * interrupts off.
454 */
455 curcpumap = CPU_ISSET(curcpu, &map);
456 CPU_CLR(curcpu, &map);
457 ipi_selected(map, IPI_RENDEZVOUS);
458
459 /* Check if the current CPU is in the map */
460 if (curcpumap != 0)
461 smp_rendezvous_action();
462
463 /*
464 * Ensure that the master CPU waits for all the other
465 * CPUs to finish the rendezvous, so that smp_rv_*
466 * pseudo-structure and the arg are guaranteed to not
467 * be in use.
468 */
469 while (atomic_load_acq_int(&smp_rv_waiters[3]) < ncpus)
470 cpu_spinwait();
471
472 mtx_unlock_spin(&smp_ipi_mtx);
473 }
474
475 void
476 smp_rendezvous(void (* setup_func)(void *),
477 void (* action_func)(void *),
478 void (* teardown_func)(void *),
479 void *arg)
480 {
481 smp_rendezvous_cpus(all_cpus, setup_func, action_func, teardown_func, arg);
482 }
483
484 static struct cpu_group group[MAXCPU];
485
486 struct cpu_group *
487 smp_topo(void)
488 {
489 char cpusetbuf[CPUSETBUFSIZ], cpusetbuf2[CPUSETBUFSIZ];
490 struct cpu_group *top;
491
492 /*
493 * Check for a fake topology request for debugging purposes.
494 */
495 switch (smp_topology) {
496 case 1:
497 /* Dual core with no sharing. */
498 top = smp_topo_1level(CG_SHARE_NONE, 2, 0);
499 break;
500 case 2:
501 /* No topology, all cpus are equal. */
502 top = smp_topo_none();
503 break;
504 case 3:
505 /* Dual core with shared L2. */
506 top = smp_topo_1level(CG_SHARE_L2, 2, 0);
507 break;
508 case 4:
509 /* quad core, shared l3 among each package, private l2. */
510 top = smp_topo_1level(CG_SHARE_L3, 4, 0);
511 break;
512 case 5:
513 /* quad core, 2 dualcore parts on each package share l2. */
514 top = smp_topo_2level(CG_SHARE_NONE, 2, CG_SHARE_L2, 2, 0);
515 break;
516 case 6:
517 /* Single-core 2xHTT */
518 top = smp_topo_1level(CG_SHARE_L1, 2, CG_FLAG_HTT);
519 break;
520 case 7:
521 /* quad core with a shared l3, 8 threads sharing L2. */
522 top = smp_topo_2level(CG_SHARE_L3, 4, CG_SHARE_L2, 8,
523 CG_FLAG_SMT);
524 break;
525 default:
526 /* Default, ask the system what it wants. */
527 top = cpu_topo();
528 break;
529 }
530 /*
531 * Verify the returned topology.
532 */
533 if (top->cg_count != mp_ncpus)
534 panic("Built bad topology at %p. CPU count %d != %d",
535 top, top->cg_count, mp_ncpus);
536 if (CPU_CMP(&top->cg_mask, &all_cpus))
537 panic("Built bad topology at %p. CPU mask (%s) != (%s)",
538 top, cpusetobj_strprint(cpusetbuf, &top->cg_mask),
539 cpusetobj_strprint(cpusetbuf2, &all_cpus));
540 return (top);
541 }
542
543 struct cpu_group *
544 smp_topo_none(void)
545 {
546 struct cpu_group *top;
547
548 top = &group[0];
549 top->cg_parent = NULL;
550 top->cg_child = NULL;
551 top->cg_mask = all_cpus;
552 top->cg_count = mp_ncpus;
553 top->cg_children = 0;
554 top->cg_level = CG_SHARE_NONE;
555 top->cg_flags = 0;
556
557 return (top);
558 }
559
560 static int
561 smp_topo_addleaf(struct cpu_group *parent, struct cpu_group *child, int share,
562 int count, int flags, int start)
563 {
564 char cpusetbuf[CPUSETBUFSIZ], cpusetbuf2[CPUSETBUFSIZ];
565 cpuset_t mask;
566 int i;
567
568 CPU_ZERO(&mask);
569 for (i = 0; i < count; i++, start++)
570 CPU_SET(start, &mask);
571 child->cg_parent = parent;
572 child->cg_child = NULL;
573 child->cg_children = 0;
574 child->cg_level = share;
575 child->cg_count = count;
576 child->cg_flags = flags;
577 child->cg_mask = mask;
578 parent->cg_children++;
579 for (; parent != NULL; parent = parent->cg_parent) {
580 if (CPU_OVERLAP(&parent->cg_mask, &child->cg_mask))
581 panic("Duplicate children in %p. mask (%s) child (%s)",
582 parent,
583 cpusetobj_strprint(cpusetbuf, &parent->cg_mask),
584 cpusetobj_strprint(cpusetbuf2, &child->cg_mask));
585 CPU_OR(&parent->cg_mask, &child->cg_mask);
586 parent->cg_count += child->cg_count;
587 }
588
589 return (start);
590 }
591
592 struct cpu_group *
593 smp_topo_1level(int share, int count, int flags)
594 {
595 struct cpu_group *child;
596 struct cpu_group *top;
597 int packages;
598 int cpu;
599 int i;
600
601 cpu = 0;
602 top = &group[0];
603 packages = mp_ncpus / count;
604 top->cg_child = child = &group[1];
605 top->cg_level = CG_SHARE_NONE;
606 for (i = 0; i < packages; i++, child++)
607 cpu = smp_topo_addleaf(top, child, share, count, flags, cpu);
608 return (top);
609 }
610
611 struct cpu_group *
612 smp_topo_2level(int l2share, int l2count, int l1share, int l1count,
613 int l1flags)
614 {
615 struct cpu_group *top;
616 struct cpu_group *l1g;
617 struct cpu_group *l2g;
618 int cpu;
619 int i;
620 int j;
621
622 cpu = 0;
623 top = &group[0];
624 l2g = &group[1];
625 top->cg_child = l2g;
626 top->cg_level = CG_SHARE_NONE;
627 top->cg_children = mp_ncpus / (l2count * l1count);
628 l1g = l2g + top->cg_children;
629 for (i = 0; i < top->cg_children; i++, l2g++) {
630 l2g->cg_parent = top;
631 l2g->cg_child = l1g;
632 l2g->cg_level = l2share;
633 for (j = 0; j < l2count; j++, l1g++)
634 cpu = smp_topo_addleaf(l2g, l1g, l1share, l1count,
635 l1flags, cpu);
636 }
637 return (top);
638 }
639
640
641 struct cpu_group *
642 smp_topo_find(struct cpu_group *top, int cpu)
643 {
644 struct cpu_group *cg;
645 cpuset_t mask;
646 int children;
647 int i;
648
649 CPU_SETOF(cpu, &mask);
650 cg = top;
651 for (;;) {
652 if (!CPU_OVERLAP(&cg->cg_mask, &mask))
653 return (NULL);
654 if (cg->cg_children == 0)
655 return (cg);
656 children = cg->cg_children;
657 for (i = 0, cg = cg->cg_child; i < children; cg++, i++)
658 if (CPU_OVERLAP(&cg->cg_mask, &mask))
659 break;
660 }
661 return (NULL);
662 }
663 #else /* !SMP */
664
665 void
666 smp_rendezvous_cpus(cpuset_t map,
667 void (*setup_func)(void *),
668 void (*action_func)(void *),
669 void (*teardown_func)(void *),
670 void *arg)
671 {
672 /*
673 * In the !SMP case we just need to ensure the same initial conditions
674 * as the SMP case.
675 */
676 spinlock_enter();
677 if (setup_func != NULL)
678 setup_func(arg);
679 if (action_func != NULL)
680 action_func(arg);
681 if (teardown_func != NULL)
682 teardown_func(arg);
683 spinlock_exit();
684 }
685
686 void
687 smp_rendezvous(void (*setup_func)(void *),
688 void (*action_func)(void *),
689 void (*teardown_func)(void *),
690 void *arg)
691 {
692
693 /* Look comments in the smp_rendezvous_cpus() case. */
694 spinlock_enter();
695 if (setup_func != NULL)
696 setup_func(arg);
697 if (action_func != NULL)
698 action_func(arg);
699 if (teardown_func != NULL)
700 teardown_func(arg);
701 spinlock_exit();
702 }
703
704 /*
705 * Provide dummy SMP support for UP kernels. Modules that need to use SMP
706 * APIs will still work using this dummy support.
707 */
708 static void
709 mp_setvariables_for_up(void *dummy)
710 {
711 mp_ncpus = 1;
712 mp_maxid = PCPU_GET(cpuid);
713 CPU_SETOF(mp_maxid, &all_cpus);
714 KASSERT(PCPU_GET(cpuid) == 0, ("UP must have a CPU ID of zero"));
715 }
716 SYSINIT(cpu_mp_setvariables, SI_SUB_TUNABLES, SI_ORDER_FIRST,
717 mp_setvariables_for_up, NULL);
718 #endif /* SMP */
719
720 void
721 smp_no_rendevous_barrier(void *dummy)
722 {
723 #ifdef SMP
724 KASSERT((!smp_started),("smp_no_rendevous called and smp is started"));
725 #endif
726 }
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