Rev 99 | Rev 109 | Go to most recent revision | Details | Compare with Previous | Last modification | View Log | RSS feed
Rev | Author | Line No. | Line |
---|---|---|---|
1 | jermar | 1 | /* |
2 | * Copyright (C) 2001-2004 Jakub Jermar |
||
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 | * |
||
9 | * - Redistributions of source code must retain the above copyright |
||
10 | * notice, this list of conditions and the following disclaimer. |
||
11 | * - 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 | * - The name of the author may not be used to endorse or promote products |
||
15 | * derived from this software without specific prior written permission. |
||
16 | * |
||
17 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR |
||
18 | * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
||
19 | * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. |
||
20 | * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, |
||
21 | * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT |
||
22 | * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
||
23 | * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
||
24 | * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
||
25 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF |
||
26 | * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
||
27 | */ |
||
28 | |||
29 | #include <proc/scheduler.h> |
||
30 | #include <proc/thread.h> |
||
31 | #include <proc/task.h> |
||
32 | #include <cpu.h> |
||
33 | #include <mm/vm.h> |
||
34 | #include <config.h> |
||
35 | #include <context.h> |
||
36 | #include <func.h> |
||
37 | #include <arch.h> |
||
38 | #include <arch/asm.h> |
||
39 | #include <list.h> |
||
68 | decky | 40 | #include <panic.h> |
1 | jermar | 41 | #include <typedefs.h> |
42 | #include <mm/page.h> |
||
43 | #include <synch/spinlock.h> |
||
76 | jermar | 44 | #include <arch/faddr.h> |
1 | jermar | 45 | |
46 | #ifdef __SMP__ |
||
11 | jermar | 47 | #include <arch/smp/atomic.h> |
1 | jermar | 48 | #endif /* __SMP__ */ |
49 | |||
50 | /* |
||
51 | * NOTE ON ATOMIC READS: |
||
52 | * Some architectures cannot read __u32 atomically. |
||
53 | * For that reason, all accesses to nrdy and the likes must be protected by spinlock. |
||
54 | */ |
||
55 | |||
56 | spinlock_t nrdylock; |
||
57 | volatile int nrdy; |
||
58 | |||
107 | decky | 59 | |
60 | /** Initialize context switching |
||
61 | * |
||
62 | * Initialize context switching and lazy FPU |
||
63 | * context switching. |
||
64 | * |
||
65 | */ |
||
52 | vana | 66 | void before_thread_runs(void) |
67 | { |
||
68 | before_thread_runs_arch(); |
||
57 | vana | 69 | fpu_context_restore(&(THREAD->saved_fpu_context)); |
52 | vana | 70 | } |
71 | |||
72 | |||
107 | decky | 73 | /** Initialize scheduler |
74 | * |
||
75 | * Initialize kernel scheduler. |
||
76 | * |
||
77 | */ |
||
1 | jermar | 78 | void scheduler_init(void) |
79 | { |
||
80 | spinlock_initialize(&nrdylock); |
||
81 | } |
||
82 | |||
107 | decky | 83 | |
84 | /** Get thread to be scheduled |
||
85 | * |
||
86 | * Get the optimal thread to be scheduled |
||
87 | * according thread accounting and scheduler |
||
88 | * policy. |
||
89 | * |
||
90 | * @return Thread to be scheduled. |
||
91 | * |
||
92 | */ |
||
1 | jermar | 93 | struct thread *find_best_thread(void) |
94 | { |
||
95 | thread_t *t; |
||
96 | runq_t *r; |
||
97 | int i, n; |
||
98 | |||
99 | loop: |
||
100 | cpu_priority_high(); |
||
101 | |||
15 | jermar | 102 | spinlock_lock(&CPU->lock); |
103 | n = CPU->nrdy; |
||
104 | spinlock_unlock(&CPU->lock); |
||
1 | jermar | 105 | |
106 | cpu_priority_low(); |
||
107 | |||
108 | if (n == 0) { |
||
109 | #ifdef __SMP__ |
||
110 | /* |
||
111 | * If the load balancing thread is not running, wake it up and |
||
112 | * set CPU-private flag that the kcpulb has been started. |
||
113 | */ |
||
15 | jermar | 114 | if (test_and_set(&CPU->kcpulbstarted) == 0) { |
115 | waitq_wakeup(&CPU->kcpulb_wq, 0); |
||
1 | jermar | 116 | goto loop; |
117 | } |
||
118 | #endif /* __SMP__ */ |
||
119 | |||
120 | /* |
||
121 | * For there was nothing to run, the CPU goes to sleep |
||
122 | * until a hardware interrupt or an IPI comes. |
||
123 | * This improves energy saving and hyperthreading. |
||
124 | * On the other hand, several hardware interrupts can be ignored. |
||
125 | */ |
||
126 | cpu_sleep(); |
||
127 | goto loop; |
||
128 | } |
||
129 | |||
130 | cpu_priority_high(); |
||
131 | |||
132 | for (i = 0; i<RQ_COUNT; i++) { |
||
15 | jermar | 133 | r = &CPU->rq[i]; |
1 | jermar | 134 | spinlock_lock(&r->lock); |
135 | if (r->n == 0) { |
||
136 | /* |
||
137 | * If this queue is empty, try a lower-priority queue. |
||
138 | */ |
||
139 | spinlock_unlock(&r->lock); |
||
140 | continue; |
||
141 | } |
||
142 | |||
143 | spinlock_lock(&nrdylock); |
||
144 | nrdy--; |
||
145 | spinlock_unlock(&nrdylock); |
||
146 | |||
15 | jermar | 147 | spinlock_lock(&CPU->lock); |
148 | CPU->nrdy--; |
||
149 | spinlock_unlock(&CPU->lock); |
||
1 | jermar | 150 | |
151 | r->n--; |
||
152 | |||
153 | /* |
||
154 | * Take the first thread from the queue. |
||
155 | */ |
||
156 | t = list_get_instance(r->rq_head.next, thread_t, rq_link); |
||
157 | list_remove(&t->rq_link); |
||
158 | |||
159 | spinlock_unlock(&r->lock); |
||
160 | |||
161 | spinlock_lock(&t->lock); |
||
15 | jermar | 162 | t->cpu = CPU; |
1 | jermar | 163 | |
164 | t->ticks = us2ticks((i+1)*10000); |
||
165 | t->pri = i; /* eventually correct rq index */ |
||
166 | |||
167 | /* |
||
168 | * Clear the X_STOLEN flag so that t can be migrated when load balancing needs emerge. |
||
169 | */ |
||
170 | t->flags &= ~X_STOLEN; |
||
171 | spinlock_unlock(&t->lock); |
||
172 | |||
173 | return t; |
||
174 | } |
||
175 | goto loop; |
||
176 | |||
177 | } |
||
178 | |||
107 | decky | 179 | |
180 | /** Prevent rq starvation |
||
181 | * |
||
182 | * Prevent low priority threads from starving in rq's. |
||
183 | * |
||
184 | * When the function decides to relink rq's, it reconnects |
||
185 | * respective pointers so that in result threads with 'pri' |
||
186 | * greater or equal 'start' are moved to a higher-priority queue. |
||
187 | * |
||
188 | * @param start Threshold priority. |
||
189 | * |
||
1 | jermar | 190 | */ |
191 | void relink_rq(int start) |
||
192 | { |
||
193 | link_t head; |
||
194 | runq_t *r; |
||
195 | int i, n; |
||
196 | |||
197 | list_initialize(&head); |
||
15 | jermar | 198 | spinlock_lock(&CPU->lock); |
199 | if (CPU->needs_relink > NEEDS_RELINK_MAX) { |
||
1 | jermar | 200 | for (i = start; i<RQ_COUNT-1; i++) { |
201 | /* remember and empty rq[i + 1] */ |
||
15 | jermar | 202 | r = &CPU->rq[i + 1]; |
1 | jermar | 203 | spinlock_lock(&r->lock); |
204 | list_concat(&head, &r->rq_head); |
||
205 | n = r->n; |
||
206 | r->n = 0; |
||
207 | spinlock_unlock(&r->lock); |
||
208 | |||
209 | /* append rq[i + 1] to rq[i] */ |
||
15 | jermar | 210 | r = &CPU->rq[i]; |
1 | jermar | 211 | spinlock_lock(&r->lock); |
212 | list_concat(&r->rq_head, &head); |
||
213 | r->n += n; |
||
214 | spinlock_unlock(&r->lock); |
||
215 | } |
||
15 | jermar | 216 | CPU->needs_relink = 0; |
1 | jermar | 217 | } |
15 | jermar | 218 | spinlock_unlock(&CPU->lock); |
1 | jermar | 219 | |
220 | } |
||
221 | |||
107 | decky | 222 | |
223 | /** The scheduler |
||
224 | * |
||
225 | * The thread scheduling procedure. |
||
226 | * |
||
1 | jermar | 227 | */ |
228 | void scheduler(void) |
||
229 | { |
||
230 | volatile pri_t pri; |
||
231 | |||
232 | pri = cpu_priority_high(); |
||
233 | |||
234 | if (haltstate) |
||
235 | halt(); |
||
236 | |||
15 | jermar | 237 | if (THREAD) { |
238 | spinlock_lock(&THREAD->lock); |
||
57 | vana | 239 | fpu_context_save(&(THREAD->saved_fpu_context)); |
15 | jermar | 240 | if (!context_save(&THREAD->saved_context)) { |
1 | jermar | 241 | /* |
242 | * This is the place where threads leave scheduler(); |
||
243 | */ |
||
22 | jermar | 244 | before_thread_runs(); |
15 | jermar | 245 | spinlock_unlock(&THREAD->lock); |
246 | cpu_priority_restore(THREAD->saved_context.pri); |
||
1 | jermar | 247 | return; |
248 | } |
||
15 | jermar | 249 | THREAD->saved_context.pri = pri; |
1 | jermar | 250 | } |
251 | |||
252 | /* |
||
253 | * We may not keep the old stack. |
||
254 | * Reason: If we kept the old stack and got blocked, for instance, in |
||
255 | * find_best_thread(), the old thread could get rescheduled by another |
||
256 | * CPU and overwrite the part of its own stack that was also used by |
||
257 | * the scheduler on this CPU. |
||
258 | * |
||
259 | * Moreover, we have to bypass the compiler-generated POP sequence |
||
260 | * which is fooled by SP being set to the very top of the stack. |
||
261 | * Therefore the scheduler() function continues in |
||
262 | * scheduler_separated_stack(). |
||
263 | */ |
||
15 | jermar | 264 | context_save(&CPU->saved_context); |
97 | jermar | 265 | context_set(&CPU->saved_context, FADDR(scheduler_separated_stack), CPU->stack, CPU_STACK_SIZE); |
15 | jermar | 266 | context_restore(&CPU->saved_context); |
1 | jermar | 267 | /* not reached */ |
268 | } |
||
269 | |||
107 | decky | 270 | |
271 | /** Scheduler stack switch wrapper |
||
272 | * |
||
273 | * Second part of the scheduler() function |
||
274 | * using new stack. Handling the actual context |
||
275 | * switch to a new thread. |
||
276 | * |
||
277 | */ |
||
1 | jermar | 278 | void scheduler_separated_stack(void) |
279 | { |
||
280 | int priority; |
||
281 | |||
15 | jermar | 282 | if (THREAD) { |
283 | switch (THREAD->state) { |
||
1 | jermar | 284 | case Running: |
15 | jermar | 285 | THREAD->state = Ready; |
286 | spinlock_unlock(&THREAD->lock); |
||
287 | thread_ready(THREAD); |
||
1 | jermar | 288 | break; |
289 | |||
290 | case Exiting: |
||
15 | jermar | 291 | frame_free((__address) THREAD->kstack); |
292 | if (THREAD->ustack) { |
||
293 | frame_free((__address) THREAD->ustack); |
||
1 | jermar | 294 | } |
295 | |||
296 | /* |
||
297 | * Detach from the containing task. |
||
298 | */ |
||
15 | jermar | 299 | spinlock_lock(&TASK->lock); |
300 | list_remove(&THREAD->th_link); |
||
301 | spinlock_unlock(&TASK->lock); |
||
1 | jermar | 302 | |
15 | jermar | 303 | spinlock_unlock(&THREAD->lock); |
1 | jermar | 304 | |
305 | spinlock_lock(&threads_lock); |
||
15 | jermar | 306 | list_remove(&THREAD->threads_link); |
1 | jermar | 307 | spinlock_unlock(&threads_lock); |
73 | vana | 308 | |
99 | jermar | 309 | spinlock_lock(&CPU->lock); |
310 | if(CPU->fpu_owner==THREAD) CPU->fpu_owner=NULL; |
||
311 | spinlock_unlock(&CPU->lock); |
||
73 | vana | 312 | |
1 | jermar | 313 | |
15 | jermar | 314 | free(THREAD); |
1 | jermar | 315 | |
316 | break; |
||
317 | |||
318 | case Sleeping: |
||
319 | /* |
||
320 | * Prefer the thread after it's woken up. |
||
321 | */ |
||
15 | jermar | 322 | THREAD->pri = -1; |
1 | jermar | 323 | |
324 | /* |
||
325 | * We need to release wq->lock which we locked in waitq_sleep(). |
||
15 | jermar | 326 | * Address of wq->lock is kept in THREAD->sleep_queue. |
1 | jermar | 327 | */ |
15 | jermar | 328 | spinlock_unlock(&THREAD->sleep_queue->lock); |
1 | jermar | 329 | |
330 | /* |
||
331 | * Check for possible requests for out-of-context invocation. |
||
332 | */ |
||
15 | jermar | 333 | if (THREAD->call_me) { |
334 | THREAD->call_me(THREAD->call_me_with); |
||
335 | THREAD->call_me = NULL; |
||
336 | THREAD->call_me_with = NULL; |
||
1 | jermar | 337 | } |
338 | |||
15 | jermar | 339 | spinlock_unlock(&THREAD->lock); |
1 | jermar | 340 | |
341 | break; |
||
342 | |||
343 | default: |
||
344 | /* |
||
345 | * Entering state is unexpected. |
||
346 | */ |
||
15 | jermar | 347 | panic("tid%d: unexpected state %s\n", THREAD->tid, thread_states[THREAD->state]); |
1 | jermar | 348 | break; |
349 | } |
||
15 | jermar | 350 | THREAD = NULL; |
1 | jermar | 351 | } |
352 | |||
15 | jermar | 353 | THREAD = find_best_thread(); |
1 | jermar | 354 | |
15 | jermar | 355 | spinlock_lock(&THREAD->lock); |
356 | priority = THREAD->pri; |
||
357 | spinlock_unlock(&THREAD->lock); |
||
1 | jermar | 358 | |
359 | relink_rq(priority); |
||
360 | |||
15 | jermar | 361 | spinlock_lock(&THREAD->lock); |
1 | jermar | 362 | |
363 | /* |
||
364 | * If both the old and the new task are the same, lots of work is avoided. |
||
365 | */ |
||
15 | jermar | 366 | if (TASK != THREAD->task) { |
1 | jermar | 367 | vm_t *m1 = NULL; |
368 | vm_t *m2; |
||
369 | |||
15 | jermar | 370 | if (TASK) { |
371 | spinlock_lock(&TASK->lock); |
||
372 | m1 = TASK->vm; |
||
373 | spinlock_unlock(&TASK->lock); |
||
1 | jermar | 374 | } |
375 | |||
15 | jermar | 376 | spinlock_lock(&THREAD->task->lock); |
377 | m2 = THREAD->task->vm; |
||
378 | spinlock_unlock(&THREAD->task->lock); |
||
1 | jermar | 379 | |
380 | /* |
||
381 | * Note that it is possible for two tasks to share one vm mapping. |
||
382 | */ |
||
383 | if (m1 != m2) { |
||
384 | /* |
||
385 | * Both tasks and vm mappings are different. |
||
386 | * Replace the old one with the new one. |
||
387 | */ |
||
388 | if (m1) { |
||
389 | vm_uninstall(m1); |
||
390 | } |
||
391 | vm_install(m2); |
||
392 | } |
||
15 | jermar | 393 | TASK = THREAD->task; |
1 | jermar | 394 | } |
395 | |||
15 | jermar | 396 | THREAD->state = Running; |
1 | jermar | 397 | |
398 | #ifdef SCHEDULER_VERBOSE |
||
15 | jermar | 399 | printf("cpu%d: tid %d (pri=%d,ticks=%d,nrdy=%d)\n", CPU->id, THREAD->tid, THREAD->pri, THREAD->ticks, CPU->nrdy); |
1 | jermar | 400 | #endif |
401 | |||
15 | jermar | 402 | context_restore(&THREAD->saved_context); |
1 | jermar | 403 | /* not reached */ |
404 | } |
||
405 | |||
107 | decky | 406 | |
1 | jermar | 407 | #ifdef __SMP__ |
107 | decky | 408 | /** Load balancing thread |
409 | * |
||
410 | * SMP load balancing thread, supervising thread supplies |
||
411 | * for the CPU it's wired to. |
||
412 | * |
||
413 | * @param arg Generic thread argument (unused). |
||
414 | * |
||
1 | jermar | 415 | */ |
416 | void kcpulb(void *arg) |
||
417 | { |
||
418 | thread_t *t; |
||
419 | int count, i, j, k = 0; |
||
420 | pri_t pri; |
||
421 | |||
422 | loop: |
||
423 | /* |
||
424 | * Sleep until there's some work to do. |
||
425 | */ |
||
15 | jermar | 426 | waitq_sleep(&CPU->kcpulb_wq); |
1 | jermar | 427 | |
428 | not_satisfied: |
||
429 | /* |
||
430 | * Calculate the number of threads that will be migrated/stolen from |
||
431 | * other CPU's. Note that situation can have changed between two |
||
432 | * passes. Each time get the most up to date counts. |
||
433 | */ |
||
434 | pri = cpu_priority_high(); |
||
15 | jermar | 435 | spinlock_lock(&CPU->lock); |
1 | jermar | 436 | count = nrdy / config.cpu_active; |
15 | jermar | 437 | count -= CPU->nrdy; |
438 | spinlock_unlock(&CPU->lock); |
||
1 | jermar | 439 | cpu_priority_restore(pri); |
440 | |||
441 | if (count <= 0) |
||
442 | goto satisfied; |
||
443 | |||
444 | /* |
||
445 | * Searching least priority queues on all CPU's first and most priority queues on all CPU's last. |
||
446 | */ |
||
447 | for (j=RQ_COUNT-1; j >= 0; j--) { |
||
448 | for (i=0; i < config.cpu_active; i++) { |
||
449 | link_t *l; |
||
450 | runq_t *r; |
||
451 | cpu_t *cpu; |
||
452 | |||
453 | cpu = &cpus[(i + k) % config.cpu_active]; |
||
454 | r = &cpu->rq[j]; |
||
455 | |||
456 | /* |
||
457 | * Not interested in ourselves. |
||
458 | * Doesn't require interrupt disabling for kcpulb is X_WIRED. |
||
459 | */ |
||
15 | jermar | 460 | if (CPU == cpu) |
1 | jermar | 461 | continue; |
462 | |||
463 | restart: pri = cpu_priority_high(); |
||
464 | spinlock_lock(&r->lock); |
||
465 | if (r->n == 0) { |
||
466 | spinlock_unlock(&r->lock); |
||
467 | cpu_priority_restore(pri); |
||
468 | continue; |
||
469 | } |
||
470 | |||
471 | t = NULL; |
||
472 | l = r->rq_head.prev; /* search rq from the back */ |
||
473 | while (l != &r->rq_head) { |
||
474 | t = list_get_instance(l, thread_t, rq_link); |
||
475 | /* |
||
476 | * We don't want to steal CPU-wired threads neither threads already stolen. |
||
477 | * The latter prevents threads from migrating between CPU's without ever being run. |
||
73 | vana | 478 | * We don't want to steal threads whose FPU context is still in CPU |
479 | */ |
||
1 | jermar | 480 | spinlock_lock(&t->lock); |
73 | vana | 481 | if ( (!(t->flags & (X_WIRED | X_STOLEN))) && (!(t->fpu_context_engaged)) ) { |
1 | jermar | 482 | /* |
483 | * Remove t from r. |
||
484 | */ |
||
485 | |||
486 | spinlock_unlock(&t->lock); |
||
487 | |||
488 | /* |
||
489 | * Here we have to avoid deadlock with relink_rq(), |
||
490 | * because it locks cpu and r in a different order than we do. |
||
491 | */ |
||
492 | if (!spinlock_trylock(&cpu->lock)) { |
||
493 | /* Release all locks and try again. */ |
||
494 | spinlock_unlock(&r->lock); |
||
495 | cpu_priority_restore(pri); |
||
496 | goto restart; |
||
497 | } |
||
498 | cpu->nrdy--; |
||
499 | spinlock_unlock(&cpu->lock); |
||
500 | |||
501 | spinlock_lock(&nrdylock); |
||
502 | nrdy--; |
||
503 | spinlock_unlock(&nrdylock); |
||
504 | |||
505 | r->n--; |
||
506 | list_remove(&t->rq_link); |
||
507 | |||
508 | break; |
||
509 | } |
||
510 | spinlock_unlock(&t->lock); |
||
511 | l = l->prev; |
||
512 | t = NULL; |
||
513 | } |
||
514 | spinlock_unlock(&r->lock); |
||
515 | |||
516 | if (t) { |
||
517 | /* |
||
518 | * Ready t on local CPU |
||
519 | */ |
||
520 | spinlock_lock(&t->lock); |
||
521 | #ifdef KCPULB_VERBOSE |
||
15 | jermar | 522 | printf("kcpulb%d: TID %d -> cpu%d, nrdy=%d, avg=%d\n", CPU->id, t->tid, CPU->id, CPU->nrdy, nrdy / config.cpu_active); |
1 | jermar | 523 | #endif |
524 | t->flags |= X_STOLEN; |
||
525 | spinlock_unlock(&t->lock); |
||
526 | |||
527 | thread_ready(t); |
||
528 | |||
529 | cpu_priority_restore(pri); |
||
530 | |||
531 | if (--count == 0) |
||
532 | goto satisfied; |
||
533 | |||
534 | /* |
||
535 | * We are not satisfied yet, focus on another CPU next time. |
||
536 | */ |
||
537 | k++; |
||
538 | |||
539 | continue; |
||
540 | } |
||
541 | cpu_priority_restore(pri); |
||
542 | } |
||
543 | } |
||
544 | |||
15 | jermar | 545 | if (CPU->nrdy) { |
1 | jermar | 546 | /* |
547 | * Be a little bit light-weight and let migrated threads run. |
||
548 | */ |
||
549 | scheduler(); |
||
550 | } |
||
551 | else { |
||
552 | /* |
||
553 | * We failed to migrate a single thread. |
||
554 | * Something more sophisticated should be done. |
||
555 | */ |
||
556 | scheduler(); |
||
557 | } |
||
558 | |||
559 | goto not_satisfied; |
||
560 | |||
561 | satisfied: |
||
562 | /* |
||
563 | * Tell find_best_thread() to wake us up later again. |
||
564 | */ |
||
15 | jermar | 565 | CPU->kcpulbstarted = 0; |
1 | jermar | 566 | goto loop; |
567 | } |
||
568 | |||
569 | #endif /* __SMP__ */ |