kernel - Major signal path adjustments to fix races, tsleep race fixes, +more
[dragonfly.git] / sys / kern / usched_dummy.c
CommitLineData
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1/*
2 * Copyright (c) 2006 The DragonFly Project. All rights reserved.
3 *
4 * This code is derived from software contributed to The DragonFly Project
5 * by Matthew Dillon <dillon@backplane.com>
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 *
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in
15 * the documentation and/or other materials provided with the
16 * distribution.
17 * 3. Neither the name of The DragonFly Project nor the names of its
18 * contributors may be used to endorse or promote products derived
19 * from this software without specific, prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
22 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
23 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
24 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
25 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
26 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
27 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
28 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
29 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
30 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
31 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * SUCH DAMAGE.
33 *
c3149361 34 * $DragonFly: src/sys/kern/usched_dummy.c,v 1.9 2008/04/21 15:24:46 dillon Exp $
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35 */
36
37#include <sys/param.h>
38#include <sys/systm.h>
39#include <sys/kernel.h>
40#include <sys/lock.h>
41#include <sys/queue.h>
42#include <sys/proc.h>
43#include <sys/rtprio.h>
44#include <sys/uio.h>
45#include <sys/sysctl.h>
46#include <sys/resourcevar.h>
47#include <sys/spinlock.h>
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48#include <machine/cpu.h>
49#include <machine/smp.h>
50
51#include <sys/thread2.h>
52#include <sys/spinlock2.h>
684a93c4 53#include <sys/mplock2.h>
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54
55#define MAXPRI 128
56#define PRIBASE_REALTIME 0
57#define PRIBASE_NORMAL MAXPRI
58#define PRIBASE_IDLE (MAXPRI * 2)
59#define PRIBASE_THREAD (MAXPRI * 3)
60#define PRIBASE_NULL (MAXPRI * 4)
61
62#define lwp_priority lwp_usdata.bsd4.priority
63#define lwp_estcpu lwp_usdata.bsd4.estcpu
64
65static void dummy_acquire_curproc(struct lwp *lp);
66static void dummy_release_curproc(struct lwp *lp);
67static void dummy_select_curproc(globaldata_t gd);
68static void dummy_setrunqueue(struct lwp *lp);
69static void dummy_schedulerclock(struct lwp *lp, sysclock_t period,
70 sysclock_t cpstamp);
71static void dummy_recalculate_estcpu(struct lwp *lp);
72static void dummy_resetpriority(struct lwp *lp);
73static void dummy_forking(struct lwp *plp, struct lwp *lp);
52cac9fb 74static void dummy_exiting(struct lwp *plp, struct proc *child);
c3149361 75static void dummy_yield(struct lwp *lp);
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76
77struct usched usched_dummy = {
78 { NULL },
79 "dummy", "Dummy DragonFly Scheduler",
80 NULL, /* default registration */
81 NULL, /* default deregistration */
82 dummy_acquire_curproc,
83 dummy_release_curproc,
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84 dummy_setrunqueue,
85 dummy_schedulerclock,
86 dummy_recalculate_estcpu,
87 dummy_resetpriority,
88 dummy_forking,
89 dummy_exiting,
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90 NULL, /* setcpumask not supported */
91 dummy_yield
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92};
93
94struct usched_dummy_pcpu {
95 int rrcount;
96 struct thread helper_thread;
97 struct lwp *uschedcp;
98};
99
100typedef struct usched_dummy_pcpu *dummy_pcpu_t;
101
102static struct usched_dummy_pcpu dummy_pcpu[MAXCPU];
103static cpumask_t dummy_curprocmask = -1;
104static cpumask_t dummy_rdyprocmask;
105static struct spinlock dummy_spin;
106static TAILQ_HEAD(rq, lwp) dummy_runq;
107static int dummy_runqcount;
108
109static int usched_dummy_rrinterval = (ESTCPUFREQ + 9) / 10;
110SYSCTL_INT(_kern, OID_AUTO, usched_dummy_rrinterval, CTLFLAG_RW,
111 &usched_dummy_rrinterval, 0, "");
112
113/*
114 * Initialize the run queues at boot time, clear cpu 0 in curprocmask
115 * to allow dummy scheduling on cpu 0.
116 */
117static void
118dummyinit(void *dummy)
119{
120 TAILQ_INIT(&dummy_runq);
121 spin_init(&dummy_spin);
da23a592 122 atomic_clear_cpumask(&dummy_curprocmask, 1);
52eedfb5 123}
ba39e2e0 124SYSINIT(runqueue, SI_BOOT2_USCHED, SI_ORDER_FIRST, dummyinit, NULL)
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125
126/*
127 * DUMMY_ACQUIRE_CURPROC
128 *
129 * This function is called when the kernel intends to return to userland.
130 * It is responsible for making the thread the current designated userland
131 * thread for this cpu, blocking if necessary.
132 *
133 * We are expected to handle userland reschedule requests here too.
134 *
135 * WARNING! THIS FUNCTION IS ALLOWED TO CAUSE THE CURRENT THREAD TO MIGRATE
136 * TO ANOTHER CPU! Because most of the kernel assumes that no migration will
137 * occur, this function is called only under very controlled circumstances.
138 *
139 * MPSAFE
140 */
141static void
142dummy_acquire_curproc(struct lwp *lp)
143{
144 globaldata_t gd = mycpu;
145 dummy_pcpu_t dd = &dummy_pcpu[gd->gd_cpuid];
146 thread_t td = lp->lwp_thread;
147
148 /*
149 * Possibly select another thread
150 */
151 if (user_resched_wanted())
152 dummy_select_curproc(gd);
153
154 /*
155 * If this cpu has no current thread, select ourself
156 */
6e3e0fe1 157 if (dd->uschedcp == lp ||
55b97a8b 158 (dd->uschedcp == NULL && TAILQ_EMPTY(&dummy_runq))) {
da23a592 159 atomic_set_cpumask(&dummy_curprocmask, gd->gd_cpumask);
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160 dd->uschedcp = lp;
161 return;
162 }
163
164 /*
165 * If this cpu's current user process thread is not our thread,
166 * deschedule ourselves and place us on the run queue, then
167 * switch away.
168 *
169 * We loop until we become the current process. Its a good idea
170 * to run any passive release(s) before we mess with the scheduler
171 * so our thread is in the expected state.
172 */
173 KKASSERT(dd->uschedcp != lp);
174 if (td->td_release)
175 td->td_release(lp->lwp_thread);
176 do {
177 crit_enter();
178 lwkt_deschedule_self(td);
179 dummy_setrunqueue(lp);
180 if ((td->td_flags & TDF_RUNQ) == 0)
fde7ac71 181 ++lp->lwp_ru.ru_nivcsw;
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182 lwkt_switch(); /* WE MAY MIGRATE TO ANOTHER CPU */
183 crit_exit();
184 gd = mycpu;
185 dd = &dummy_pcpu[gd->gd_cpuid];
4643740a 186 KKASSERT((lp->lwp_mpflags & LWP_MP_ONRUNQ) == 0);
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187 } while (dd->uschedcp != lp);
188}
189
190/*
191 * DUMMY_RELEASE_CURPROC
192 *
193 * This routine detaches the current thread from the userland scheduler,
194 * usually because the thread needs to run in the kernel (at kernel priority)
195 * for a while.
196 *
197 * This routine is also responsible for selecting a new thread to
198 * make the current thread.
199 *
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200 * MPSAFE
201 */
202static void
203dummy_release_curproc(struct lwp *lp)
204{
205 globaldata_t gd = mycpu;
206 dummy_pcpu_t dd = &dummy_pcpu[gd->gd_cpuid];
207
4643740a 208 KKASSERT((lp->lwp_mpflags & LWP_MP_ONRUNQ) == 0);
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209 if (dd->uschedcp == lp) {
210 dummy_select_curproc(gd);
211 }
212}
213
214/*
215 * DUMMY_SELECT_CURPROC
216 *
217 * Select a new current process for this cpu. This satisfies a user
218 * scheduler reschedule request so clear that too.
219 *
220 * This routine is also responsible for equal-priority round-robining,
221 * typically triggered from dummy_schedulerclock(). In our dummy example
222 * all the 'user' threads are LWKT scheduled all at once and we just
223 * call lwkt_switch().
224 *
225 * MPSAFE
226 */
227static
228void
229dummy_select_curproc(globaldata_t gd)
230{
231 dummy_pcpu_t dd = &dummy_pcpu[gd->gd_cpuid];
232 struct lwp *lp;
233
234 clear_user_resched();
287a8577 235 spin_lock(&dummy_spin);
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236 if ((lp = TAILQ_FIRST(&dummy_runq)) == NULL) {
237 dd->uschedcp = NULL;
da23a592 238 atomic_clear_cpumask(&dummy_curprocmask, gd->gd_cpumask);
287a8577 239 spin_unlock(&dummy_spin);
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240 } else {
241 --dummy_runqcount;
242 TAILQ_REMOVE(&dummy_runq, lp, lwp_procq);
4643740a 243 atomic_clear_int(&lp->lwp_mpflags, LWP_MP_ONRUNQ);
52eedfb5 244 dd->uschedcp = lp;
da23a592 245 atomic_set_cpumask(&dummy_curprocmask, gd->gd_cpumask);
287a8577 246 spin_unlock(&dummy_spin);
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247#ifdef SMP
248 lwkt_acquire(lp->lwp_thread);
249#endif
250 lwkt_schedule(lp->lwp_thread);
251 }
252}
253
254/*
255 * DUMMY_SETRUNQUEUE
256 *
257 * This routine is called to schedule a new user process after a fork.
258 * The scheduler module itself might also call this routine to place
259 * the current process on the userland scheduler's run queue prior
260 * to calling dummy_select_curproc().
261 *
4643740a 262 * The caller may set LWP_PASSIVE_ACQ in lwp_flags to indicate that we should
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263 * attempt to leave the thread on the current cpu.
264 *
265 * MPSAFE
266 */
267static void
268dummy_setrunqueue(struct lwp *lp)
269{
270 globaldata_t gd = mycpu;
271 dummy_pcpu_t dd = &dummy_pcpu[gd->gd_cpuid];
272 cpumask_t mask;
273 int cpuid;
274
275 if (dd->uschedcp == NULL) {
276 dd->uschedcp = lp;
da23a592 277 atomic_set_cpumask(&dummy_curprocmask, gd->gd_cpumask);
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278 lwkt_schedule(lp->lwp_thread);
279 } else {
280 /*
281 * Add to our global runq
282 */
4643740a 283 KKASSERT((lp->lwp_mpflags & LWP_MP_ONRUNQ) == 0);
287a8577 284 spin_lock(&dummy_spin);
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285 ++dummy_runqcount;
286 TAILQ_INSERT_TAIL(&dummy_runq, lp, lwp_procq);
4643740a 287 atomic_set_int(&lp->lwp_mpflags, LWP_MP_ONRUNQ);
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288#ifdef SMP
289 lwkt_giveaway(lp->lwp_thread);
290#endif
291
292 /* lp = TAILQ_FIRST(&dummy_runq); */
293
294 /*
295 * Notify the next available cpu. P.S. some
296 * cpu affinity could be done here.
297 *
298 * The rdyprocmask bit placeholds the knowledge that there
299 * is a process on the runq that needs service. If the
300 * helper thread cannot find a home for it it will forward
301 * the request to another available cpu.
302 */
303 mask = ~dummy_curprocmask & dummy_rdyprocmask &
304 gd->gd_other_cpus;
305 if (mask) {
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306 cpuid = BSFCPUMASK(mask);
307 atomic_clear_cpumask(&dummy_rdyprocmask, CPUMASK(cpuid));
287a8577 308 spin_unlock(&dummy_spin);
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309 lwkt_schedule(&dummy_pcpu[cpuid].helper_thread);
310 } else {
287a8577 311 spin_unlock(&dummy_spin);
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312 }
313 }
314}
315
316/*
317 * This routine is called from a systimer IPI. Thus it is called with
318 * a critical section held. Any spinlocks we get here that are also
319 * obtained in other procedures must be proected by a critical section
320 * in those other procedures to avoid a deadlock.
321 *
322 * The MP lock may or may not be held on entry and cannot be obtained
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323 * by this routine (because it is called from a systimer IPI). Additionally,
324 * because this is equivalent to a FAST interrupt, spinlocks cannot be used
325 * (or at least, you have to check that gd_spin* counts are 0 before you
326 * can).
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327 *
328 * This routine is called at ESTCPUFREQ on each cpu independantly.
329 *
330 * This routine typically queues a reschedule request, which will cause
331 * the scheduler's BLAH_select_curproc() to be called as soon as possible.
332 *
333 * MPSAFE
334 */
335static
336void
337dummy_schedulerclock(struct lwp *lp, sysclock_t period, sysclock_t cpstamp)
338{
339 globaldata_t gd = mycpu;
340 dummy_pcpu_t dd = &dummy_pcpu[gd->gd_cpuid];
341
342 if (++dd->rrcount >= usched_dummy_rrinterval) {
343 dd->rrcount = 0;
344 need_user_resched();
345 }
346}
347
348/*
349 * DUMMY_RECALCULATE_ESTCPU
350 *
351 * Called once a second for any process that is running or has slept
352 * for less then 2 seconds.
353 *
354 * MPSAFE
355 */
356static
357void
358dummy_recalculate_estcpu(struct lwp *lp)
359{
360}
361
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362/*
363 * MPSAFE
364 */
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365static
366void
367dummy_yield(struct lwp *lp)
368{
369 need_user_resched();
370}
371
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372/*
373 * DUMMY_RESETPRIORITY
374 *
375 * This routine is called after the kernel has potentially modified
376 * the lwp_rtprio structure. The target process may be running or sleeping
377 * or scheduled but not yet running or owned by another cpu. Basically,
378 * it can be in virtually any state.
379 *
380 * This routine is called by fork1() for initial setup with the process
381 * of the run queue, and also may be called normally with the process on or
382 * off the run queue.
383 *
384 * MPSAFE
385 */
386static void
387dummy_resetpriority(struct lwp *lp)
388{
389 /* XXX spinlock usually needed */
390 /*
391 * Set p_priority for general process comparisons
392 */
393 switch(lp->lwp_rtprio.type) {
394 case RTP_PRIO_REALTIME:
395 lp->lwp_priority = PRIBASE_REALTIME + lp->lwp_rtprio.prio;
396 return;
397 case RTP_PRIO_NORMAL:
398 lp->lwp_priority = PRIBASE_NORMAL + lp->lwp_rtprio.prio;
399 break;
400 case RTP_PRIO_IDLE:
401 lp->lwp_priority = PRIBASE_IDLE + lp->lwp_rtprio.prio;
402 return;
403 case RTP_PRIO_THREAD:
404 lp->lwp_priority = PRIBASE_THREAD + lp->lwp_rtprio.prio;
405 return;
406 }
407 /* XXX spinlock usually needed */
408}
409
410
411/*
412 * DUMMY_FORKING
413 *
414 * Called from fork1() when a new child process is being created. Allows
415 * the scheduler to predispose the child process before it gets scheduled.
416 *
417 * MPSAFE
418 */
419static void
420dummy_forking(struct lwp *plp, struct lwp *lp)
421{
422 lp->lwp_estcpu = plp->lwp_estcpu;
423#if 0
424 ++plp->lwp_estcpu;
425#endif
426}
427
428/*
429 * DUMMY_EXITING
430 *
431 * Called when the parent reaps a child. Typically used to propogate cpu
432 * use by the child back to the parent as part of a batch detection
433 * heuristic.
434 *
435 * NOTE: cpu use is not normally back-propogated to PID 1.
436 *
437 * MPSAFE
438 */
439static void
52cac9fb 440dummy_exiting(struct lwp *plp, struct proc *child)
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441{
442}
443
444/*
445 * SMP systems may need a scheduler helper thread. This is how one can be
446 * setup.
447 *
448 * We use a neat LWKT scheduling trick to interlock the helper thread. It
449 * is possible to deschedule an LWKT thread and then do some work before
450 * switching away. The thread can be rescheduled at any time, even before
451 * we switch away.
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452 *
453 * MPSAFE
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454 */
455#ifdef SMP
456
457static void
458dummy_sched_thread(void *dummy)
459{
460 globaldata_t gd;
461 dummy_pcpu_t dd;
462 struct lwp *lp;
463 cpumask_t cpumask;
464 cpumask_t tmpmask;
465 int cpuid;
466 int tmpid;
467
468 gd = mycpu;
469 cpuid = gd->gd_cpuid;
470 dd = &dummy_pcpu[cpuid];
da23a592 471 cpumask = CPUMASK(cpuid);
52eedfb5 472
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473 for (;;) {
474 lwkt_deschedule_self(gd->gd_curthread); /* interlock */
da23a592 475 atomic_set_cpumask(&dummy_rdyprocmask, cpumask);
287a8577 476 spin_lock(&dummy_spin);
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477 if (dd->uschedcp) {
478 /*
479 * We raced another cpu trying to schedule a thread onto us.
480 * If the runq isn't empty hit another free cpu.
481 */
482 tmpmask = ~dummy_curprocmask & dummy_rdyprocmask &
483 gd->gd_other_cpus;
484 if (tmpmask && dummy_runqcount) {
da23a592 485 tmpid = BSFCPUMASK(tmpmask);
52eedfb5 486 KKASSERT(tmpid != cpuid);
da23a592 487 atomic_clear_cpumask(&dummy_rdyprocmask, CPUMASK(tmpid));
287a8577 488 spin_unlock(&dummy_spin);
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489 lwkt_schedule(&dummy_pcpu[tmpid].helper_thread);
490 } else {
287a8577 491 spin_unlock(&dummy_spin);
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492 }
493 } else if ((lp = TAILQ_FIRST(&dummy_runq)) != NULL) {
494 --dummy_runqcount;
495 TAILQ_REMOVE(&dummy_runq, lp, lwp_procq);
4643740a 496 atomic_clear_int(&lp->lwp_mpflags, LWP_MP_ONRUNQ);
52eedfb5 497 dd->uschedcp = lp;
da23a592 498 atomic_set_cpumask(&dummy_curprocmask, cpumask);
287a8577 499 spin_unlock(&dummy_spin);
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500#ifdef SMP
501 lwkt_acquire(lp->lwp_thread);
502#endif
503 lwkt_schedule(lp->lwp_thread);
504 } else {
287a8577 505 spin_unlock(&dummy_spin);
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506 }
507 lwkt_switch();
508 }
509}
510
511/*
512 * Setup our scheduler helpers. Note that curprocmask bit 0 has already
513 * been cleared by rqinit() and we should not mess with it further.
514 */
515static void
516dummy_sched_thread_cpu_init(void)
517{
518 int i;
519
520 if (bootverbose)
6ea70f76 521 kprintf("start dummy scheduler helpers on cpus:");
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522
523 for (i = 0; i < ncpus; ++i) {
524 dummy_pcpu_t dd = &dummy_pcpu[i];
da23a592 525 cpumask_t mask = CPUMASK(i);
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526
527 if ((mask & smp_active_mask) == 0)
528 continue;
529
530 if (bootverbose)
6ea70f76 531 kprintf(" %d", i);
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532
533 lwkt_create(dummy_sched_thread, NULL, NULL, &dd->helper_thread,
4643740a 534 TDF_NOSTART, i, "dsched %d", i);
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535
536 /*
537 * Allow user scheduling on the target cpu. cpu #0 has already
538 * been enabled in rqinit().
539 */
540 if (i)
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541 atomic_clear_cpumask(&dummy_curprocmask, mask);
542 atomic_set_cpumask(&dummy_rdyprocmask, mask);
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543 }
544 if (bootverbose)
6ea70f76 545 kprintf("\n");
52eedfb5 546}
ba39e2e0 547SYSINIT(uschedtd, SI_BOOT2_USCHED, SI_ORDER_SECOND,
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548 dummy_sched_thread_cpu_init, NULL)
549
550#endif
551