2 * Copyright (c) 2006 The DragonFly Project. All rights reserved.
4 * This code is derived from software contributed to The DragonFly Project
5 * by Matthew Dillon <dillon@backplane.com>
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
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
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.
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
34 * $DragonFly: src/sys/kern/usched_dummy.c,v 1.9 2008/04/21 15:24:46 dillon Exp $
37 #include <sys/param.h>
38 #include <sys/systm.h>
39 #include <sys/kernel.h>
41 #include <sys/queue.h>
43 #include <sys/rtprio.h>
45 #include <sys/sysctl.h>
46 #include <sys/resourcevar.h>
47 #include <sys/spinlock.h>
48 #include <machine/cpu.h>
49 #include <machine/smp.h>
51 #include <sys/thread2.h>
52 #include <sys/spinlock2.h>
55 #define PRIBASE_REALTIME 0
56 #define PRIBASE_NORMAL MAXPRI
57 #define PRIBASE_IDLE (MAXPRI * 2)
58 #define PRIBASE_THREAD (MAXPRI * 3)
59 #define PRIBASE_NULL (MAXPRI * 4)
61 #define lwp_priority lwp_usdata.bsd4.priority
62 #define lwp_estcpu lwp_usdata.bsd4.estcpu
64 static void dummy_acquire_curproc(struct lwp *lp);
65 static void dummy_release_curproc(struct lwp *lp);
66 static void dummy_select_curproc(globaldata_t gd);
67 static void dummy_setrunqueue(struct lwp *lp);
68 static void dummy_schedulerclock(struct lwp *lp, sysclock_t period,
70 static void dummy_recalculate_estcpu(struct lwp *lp);
71 static void dummy_resetpriority(struct lwp *lp);
72 static void dummy_forking(struct lwp *plp, struct lwp *lp);
73 static void dummy_exiting(struct lwp *plp, struct lwp *lp);
74 static void dummy_yield(struct lwp *lp);
76 struct usched usched_dummy = {
78 "dummy", "Dummy DragonFly Scheduler",
79 NULL, /* default registration */
80 NULL, /* default deregistration */
81 dummy_acquire_curproc,
82 dummy_release_curproc,
85 dummy_recalculate_estcpu,
89 NULL, /* setcpumask not supported */
93 struct usched_dummy_pcpu {
95 struct thread helper_thread;
99 typedef struct usched_dummy_pcpu *dummy_pcpu_t;
101 static struct usched_dummy_pcpu dummy_pcpu[MAXCPU];
102 static cpumask_t dummy_curprocmask = -1;
103 static cpumask_t dummy_rdyprocmask;
104 static struct spinlock dummy_spin;
105 static TAILQ_HEAD(rq, lwp) dummy_runq;
106 static int dummy_runqcount;
108 static int usched_dummy_rrinterval = (ESTCPUFREQ + 9) / 10;
109 SYSCTL_INT(_kern, OID_AUTO, usched_dummy_rrinterval, CTLFLAG_RW,
110 &usched_dummy_rrinterval, 0, "");
113 * Initialize the run queues at boot time, clear cpu 0 in curprocmask
114 * to allow dummy scheduling on cpu 0.
117 dummyinit(void *dummy)
119 TAILQ_INIT(&dummy_runq);
120 spin_init(&dummy_spin);
121 atomic_clear_int(&dummy_curprocmask, 1);
123 SYSINIT(runqueue, SI_BOOT2_USCHED, SI_ORDER_FIRST, dummyinit, NULL)
126 * DUMMY_ACQUIRE_CURPROC
128 * This function is called when the kernel intends to return to userland.
129 * It is responsible for making the thread the current designated userland
130 * thread for this cpu, blocking if necessary.
132 * We are expected to handle userland reschedule requests here too.
134 * WARNING! THIS FUNCTION IS ALLOWED TO CAUSE THE CURRENT THREAD TO MIGRATE
135 * TO ANOTHER CPU! Because most of the kernel assumes that no migration will
136 * occur, this function is called only under very controlled circumstances.
141 dummy_acquire_curproc(struct lwp *lp)
143 globaldata_t gd = mycpu;
144 dummy_pcpu_t dd = &dummy_pcpu[gd->gd_cpuid];
145 thread_t td = lp->lwp_thread;
148 * Possibly select another thread
150 if (user_resched_wanted())
151 dummy_select_curproc(gd);
154 * If this cpu has no current thread, select ourself
156 if (dd->uschedcp == NULL && TAILQ_EMPTY(&dummy_runq)) {
157 atomic_set_int(&dummy_curprocmask, gd->gd_cpumask);
163 * If this cpu's current user process thread is not our thread,
164 * deschedule ourselves and place us on the run queue, then
167 * We loop until we become the current process. Its a good idea
168 * to run any passive release(s) before we mess with the scheduler
169 * so our thread is in the expected state.
171 KKASSERT(dd->uschedcp != lp);
173 td->td_release(lp->lwp_thread);
176 lwkt_deschedule_self(td);
177 dummy_setrunqueue(lp);
178 if ((td->td_flags & TDF_RUNQ) == 0)
179 ++lp->lwp_ru.ru_nivcsw;
180 lwkt_switch(); /* WE MAY MIGRATE TO ANOTHER CPU */
183 dd = &dummy_pcpu[gd->gd_cpuid];
184 KKASSERT((lp->lwp_flag & LWP_ONRUNQ) == 0);
185 } while (dd->uschedcp != lp);
189 * DUMMY_RELEASE_CURPROC
191 * This routine detaches the current thread from the userland scheduler,
192 * usually because the thread needs to run in the kernel (at kernel priority)
195 * This routine is also responsible for selecting a new thread to
196 * make the current thread.
198 * WARNING! The MP lock may be in an unsynchronized state due to the
199 * way get_mplock() works and the fact that this function may be called
200 * from a passive release during a lwkt_switch(). try_mplock() will deal
201 * with this for us but you should be aware that td_mpcount may not be
207 dummy_release_curproc(struct lwp *lp)
209 globaldata_t gd = mycpu;
210 dummy_pcpu_t dd = &dummy_pcpu[gd->gd_cpuid];
212 KKASSERT((lp->lwp_flag & LWP_ONRUNQ) == 0);
213 if (dd->uschedcp == lp) {
214 dummy_select_curproc(gd);
219 * DUMMY_SELECT_CURPROC
221 * Select a new current process for this cpu. This satisfies a user
222 * scheduler reschedule request so clear that too.
224 * This routine is also responsible for equal-priority round-robining,
225 * typically triggered from dummy_schedulerclock(). In our dummy example
226 * all the 'user' threads are LWKT scheduled all at once and we just
227 * call lwkt_switch().
233 dummy_select_curproc(globaldata_t gd)
235 dummy_pcpu_t dd = &dummy_pcpu[gd->gd_cpuid];
238 clear_user_resched();
239 spin_lock_wr(&dummy_spin);
240 if ((lp = TAILQ_FIRST(&dummy_runq)) == NULL) {
242 atomic_clear_int(&dummy_curprocmask, gd->gd_cpumask);
243 spin_unlock_wr(&dummy_spin);
246 TAILQ_REMOVE(&dummy_runq, lp, lwp_procq);
247 lp->lwp_flag &= ~LWP_ONRUNQ;
249 atomic_set_int(&dummy_curprocmask, gd->gd_cpumask);
250 spin_unlock_wr(&dummy_spin);
252 lwkt_acquire(lp->lwp_thread);
254 lwkt_schedule(lp->lwp_thread);
261 * This routine is called to schedule a new user process after a fork.
262 * The scheduler module itself might also call this routine to place
263 * the current process on the userland scheduler's run queue prior
264 * to calling dummy_select_curproc().
266 * The caller may set P_PASSIVE_ACQ in p_flag to indicate that we should
267 * attempt to leave the thread on the current cpu.
272 dummy_setrunqueue(struct lwp *lp)
274 globaldata_t gd = mycpu;
275 dummy_pcpu_t dd = &dummy_pcpu[gd->gd_cpuid];
279 if (dd->uschedcp == NULL) {
281 atomic_set_int(&dummy_curprocmask, gd->gd_cpumask);
282 lwkt_schedule(lp->lwp_thread);
285 * Add to our global runq
287 KKASSERT((lp->lwp_flag & LWP_ONRUNQ) == 0);
288 spin_lock_wr(&dummy_spin);
290 TAILQ_INSERT_TAIL(&dummy_runq, lp, lwp_procq);
291 lp->lwp_flag |= LWP_ONRUNQ;
293 lwkt_giveaway(lp->lwp_thread);
296 /* lp = TAILQ_FIRST(&dummy_runq); */
299 * Notify the next available cpu. P.S. some
300 * cpu affinity could be done here.
302 * The rdyprocmask bit placeholds the knowledge that there
303 * is a process on the runq that needs service. If the
304 * helper thread cannot find a home for it it will forward
305 * the request to another available cpu.
307 mask = ~dummy_curprocmask & dummy_rdyprocmask &
311 atomic_clear_int(&dummy_rdyprocmask, 1 << cpuid);
312 spin_unlock_wr(&dummy_spin);
313 lwkt_schedule(&dummy_pcpu[cpuid].helper_thread);
315 spin_unlock_wr(&dummy_spin);
321 * This routine is called from a systimer IPI. Thus it is called with
322 * a critical section held. Any spinlocks we get here that are also
323 * obtained in other procedures must be proected by a critical section
324 * in those other procedures to avoid a deadlock.
326 * The MP lock may or may not be held on entry and cannot be obtained
327 * by this routine (because it is called from a systimer IPI). Additionally,
328 * because this is equivalent to a FAST interrupt, spinlocks cannot be used
329 * (or at least, you have to check that gd_spin* counts are 0 before you
332 * This routine is called at ESTCPUFREQ on each cpu independantly.
334 * This routine typically queues a reschedule request, which will cause
335 * the scheduler's BLAH_select_curproc() to be called as soon as possible.
341 dummy_schedulerclock(struct lwp *lp, sysclock_t period, sysclock_t cpstamp)
343 globaldata_t gd = mycpu;
344 dummy_pcpu_t dd = &dummy_pcpu[gd->gd_cpuid];
346 if (++dd->rrcount >= usched_dummy_rrinterval) {
353 * DUMMY_RECALCULATE_ESTCPU
355 * Called once a second for any process that is running or has slept
356 * for less then 2 seconds.
362 dummy_recalculate_estcpu(struct lwp *lp)
368 dummy_yield(struct lwp *lp)
374 * DUMMY_RESETPRIORITY
376 * This routine is called after the kernel has potentially modified
377 * the lwp_rtprio structure. The target process may be running or sleeping
378 * or scheduled but not yet running or owned by another cpu. Basically,
379 * it can be in virtually any state.
381 * This routine is called by fork1() for initial setup with the process
382 * of the run queue, and also may be called normally with the process on or
388 dummy_resetpriority(struct lwp *lp)
390 /* XXX spinlock usually needed */
392 * Set p_priority for general process comparisons
394 switch(lp->lwp_rtprio.type) {
395 case RTP_PRIO_REALTIME:
396 lp->lwp_priority = PRIBASE_REALTIME + lp->lwp_rtprio.prio;
398 case RTP_PRIO_NORMAL:
399 lp->lwp_priority = PRIBASE_NORMAL + lp->lwp_rtprio.prio;
402 lp->lwp_priority = PRIBASE_IDLE + lp->lwp_rtprio.prio;
404 case RTP_PRIO_THREAD:
405 lp->lwp_priority = PRIBASE_THREAD + lp->lwp_rtprio.prio;
408 /* XXX spinlock usually needed */
415 * Called from fork1() when a new child process is being created. Allows
416 * the scheduler to predispose the child process before it gets scheduled.
421 dummy_forking(struct lwp *plp, struct lwp *lp)
423 lp->lwp_estcpu = plp->lwp_estcpu;
432 * Called when the parent reaps a child. Typically used to propogate cpu
433 * use by the child back to the parent as part of a batch detection
436 * NOTE: cpu use is not normally back-propogated to PID 1.
441 dummy_exiting(struct lwp *plp, struct lwp *lp)
446 * SMP systems may need a scheduler helper thread. This is how one can be
449 * We use a neat LWKT scheduling trick to interlock the helper thread. It
450 * is possible to deschedule an LWKT thread and then do some work before
451 * switching away. The thread can be rescheduled at any time, even before
457 dummy_sched_thread(void *dummy)
468 cpuid = gd->gd_cpuid;
469 dd = &dummy_pcpu[cpuid];
470 cpumask = 1 << cpuid;
473 * Our Scheduler helper thread does not need to hold the MP lock
478 lwkt_deschedule_self(gd->gd_curthread); /* interlock */
479 atomic_set_int(&dummy_rdyprocmask, cpumask);
480 spin_lock_wr(&dummy_spin);
483 * We raced another cpu trying to schedule a thread onto us.
484 * If the runq isn't empty hit another free cpu.
486 tmpmask = ~dummy_curprocmask & dummy_rdyprocmask &
488 if (tmpmask && dummy_runqcount) {
489 tmpid = bsfl(tmpmask);
490 KKASSERT(tmpid != cpuid);
491 atomic_clear_int(&dummy_rdyprocmask, 1 << tmpid);
492 spin_unlock_wr(&dummy_spin);
493 lwkt_schedule(&dummy_pcpu[tmpid].helper_thread);
495 spin_unlock_wr(&dummy_spin);
497 } else if ((lp = TAILQ_FIRST(&dummy_runq)) != NULL) {
499 TAILQ_REMOVE(&dummy_runq, lp, lwp_procq);
500 lp->lwp_flag &= ~LWP_ONRUNQ;
502 atomic_set_int(&dummy_curprocmask, cpumask);
503 spin_unlock_wr(&dummy_spin);
505 lwkt_acquire(lp->lwp_thread);
507 lwkt_schedule(lp->lwp_thread);
509 spin_unlock_wr(&dummy_spin);
516 * Setup our scheduler helpers. Note that curprocmask bit 0 has already
517 * been cleared by rqinit() and we should not mess with it further.
520 dummy_sched_thread_cpu_init(void)
525 kprintf("start dummy scheduler helpers on cpus:");
527 for (i = 0; i < ncpus; ++i) {
528 dummy_pcpu_t dd = &dummy_pcpu[i];
529 cpumask_t mask = 1 << i;
531 if ((mask & smp_active_mask) == 0)
537 lwkt_create(dummy_sched_thread, NULL, NULL, &dd->helper_thread,
538 TDF_STOPREQ, i, "dsched %d", i);
541 * Allow user scheduling on the target cpu. cpu #0 has already
542 * been enabled in rqinit().
545 atomic_clear_int(&dummy_curprocmask, mask);
546 atomic_set_int(&dummy_rdyprocmask, mask);
551 SYSINIT(uschedtd, SI_BOOT2_USCHED, SI_ORDER_SECOND,
552 dummy_sched_thread_cpu_init, NULL)