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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>
378 jermar 32
#include <mm/heap.h>
33
#include <mm/frame.h>
34
#include <mm/page.h>
703 jermar 35
#include <mm/as.h>
378 jermar 36
#include <arch/asm.h>
37
#include <arch/faddr.h>
38
#include <arch/atomic.h>
39
#include <synch/spinlock.h>
1 jermar 40
#include <config.h>
41
#include <context.h>
42
#include <func.h>
43
#include <arch.h>
44
#include <list.h>
68 decky 45
#include <panic.h>
1 jermar 46
#include <typedefs.h>
378 jermar 47
#include <cpu.h>
195 vana 48
#include <print.h>
227 jermar 49
#include <debug.h>
1 jermar 50
 
475 jermar 51
atomic_t nrdy;
195 vana 52
 
118 jermar 53
/** Take actions before new thread runs
107 decky 54
 *
118 jermar 55
 * Perform actions that need to be
56
 * taken before the newly selected
57
 * tread is passed control.
107 decky 58
 *
59
 */
52 vana 60
void before_thread_runs(void)
61
{
309 palkovsky 62
    before_thread_runs_arch();
458 decky 63
#ifdef CONFIG_FPU_LAZY
309 palkovsky 64
    if(THREAD==CPU->fpu_owner)
65
        fpu_enable();
66
    else
67
        fpu_disable();
68
#else
69
    fpu_enable();
70
    if (THREAD->fpu_context_exists)
71
        fpu_context_restore(&(THREAD->saved_fpu_context));
72
    else {
73
        fpu_init();
74
        THREAD->fpu_context_exists=1;
75
    }
76
#endif
52 vana 77
}
78
 
458 decky 79
#ifdef CONFIG_FPU_LAZY
309 palkovsky 80
void scheduler_fpu_lazy_request(void)
81
{
82
    fpu_enable();
83
    if (CPU->fpu_owner != NULL) {  
84
        fpu_context_save(&CPU->fpu_owner->saved_fpu_context);
85
        /* don't prevent migration */
86
        CPU->fpu_owner->fpu_context_engaged=0;
87
    }
88
    if (THREAD->fpu_context_exists)
89
        fpu_context_restore(&THREAD->saved_fpu_context);
90
    else {
91
        fpu_init();
92
        THREAD->fpu_context_exists=1;
93
    }
94
    CPU->fpu_owner=THREAD;
95
    THREAD->fpu_context_engaged = 1;
96
}
97
#endif
52 vana 98
 
107 decky 99
/** Initialize scheduler
100
 *
101
 * Initialize kernel scheduler.
102
 *
103
 */
1 jermar 104
void scheduler_init(void)
105
{
106
}
107
 
107 decky 108
 
109
/** Get thread to be scheduled
110
 *
111
 * Get the optimal thread to be scheduled
109 jermar 112
 * according to thread accounting and scheduler
107 decky 113
 * policy.
114
 *
115
 * @return Thread to be scheduled.
116
 *
117
 */
483 jermar 118
static thread_t *find_best_thread(void)
1 jermar 119
{
120
    thread_t *t;
121
    runq_t *r;
122
    int i, n;
123
 
227 jermar 124
    ASSERT(CPU != NULL);
125
 
1 jermar 126
loop:
413 jermar 127
    interrupts_disable();
1 jermar 128
 
15 jermar 129
    spinlock_lock(&CPU->lock);
130
    n = CPU->nrdy;
131
    spinlock_unlock(&CPU->lock);
1 jermar 132
 
413 jermar 133
    interrupts_enable();
1 jermar 134
 
135
    if (n == 0) {
458 decky 136
        #ifdef CONFIG_SMP
1 jermar 137
        /*
138
         * If the load balancing thread is not running, wake it up and
139
         * set CPU-private flag that the kcpulb has been started.
140
         */
15 jermar 141
        if (test_and_set(&CPU->kcpulbstarted) == 0) {
125 jermar 142
            waitq_wakeup(&CPU->kcpulb_wq, 0);
1 jermar 143
            goto loop;
144
        }
458 decky 145
        #endif /* CONFIG_SMP */
1 jermar 146
 
147
        /*
148
         * For there was nothing to run, the CPU goes to sleep
149
         * until a hardware interrupt or an IPI comes.
150
         * This improves energy saving and hyperthreading.
151
         * On the other hand, several hardware interrupts can be ignored.
152
         */
153
         cpu_sleep();
154
         goto loop;
155
    }
156
 
413 jermar 157
    interrupts_disable();
114 jermar 158
 
159
    i = 0;
160
retry:
161
    for (; i<RQ_COUNT; i++) {
15 jermar 162
        r = &CPU->rq[i];
1 jermar 163
        spinlock_lock(&r->lock);
164
        if (r->n == 0) {
165
            /*
166
             * If this queue is empty, try a lower-priority queue.
167
             */
168
            spinlock_unlock(&r->lock);
169
            continue;
170
        }
213 jermar 171
 
115 jermar 172
        /* avoid deadlock with relink_rq() */
114 jermar 173
        if (!spinlock_trylock(&CPU->lock)) {
174
            /*
175
             * Unlock r and try again.
176
             */
177
            spinlock_unlock(&r->lock);
178
            goto retry;
179
        }
15 jermar 180
        CPU->nrdy--;
181
        spinlock_unlock(&CPU->lock);
1 jermar 182
 
475 jermar 183
        atomic_dec(&nrdy);
1 jermar 184
        r->n--;
185
 
186
        /*
187
         * Take the first thread from the queue.
188
         */
189
        t = list_get_instance(r->rq_head.next, thread_t, rq_link);
190
        list_remove(&t->rq_link);
191
 
192
        spinlock_unlock(&r->lock);
193
 
194
        spinlock_lock(&t->lock);
15 jermar 195
        t->cpu = CPU;
1 jermar 196
 
197
        t->ticks = us2ticks((i+1)*10000);
413 jermar 198
        t->priority = i;    /* eventually correct rq index */
1 jermar 199
 
200
        /*
201
         * Clear the X_STOLEN flag so that t can be migrated when load balancing needs emerge.
202
         */
203
        t->flags &= ~X_STOLEN;
204
        spinlock_unlock(&t->lock);
205
 
206
        return t;
207
    }
208
    goto loop;
209
 
210
}
211
 
107 decky 212
 
213
/** Prevent rq starvation
214
 *
215
 * Prevent low priority threads from starving in rq's.
216
 *
217
 * When the function decides to relink rq's, it reconnects
218
 * respective pointers so that in result threads with 'pri'
219
 * greater or equal 'start' are moved to a higher-priority queue.
220
 *
221
 * @param start Threshold priority.
222
 *
1 jermar 223
 */
452 decky 224
static void relink_rq(int start)
1 jermar 225
{
226
    link_t head;
227
    runq_t *r;
228
    int i, n;
229
 
230
    list_initialize(&head);
15 jermar 231
    spinlock_lock(&CPU->lock);
232
    if (CPU->needs_relink > NEEDS_RELINK_MAX) {
1 jermar 233
        for (i = start; i<RQ_COUNT-1; i++) {
234
            /* remember and empty rq[i + 1] */
15 jermar 235
            r = &CPU->rq[i + 1];
1 jermar 236
            spinlock_lock(&r->lock);
237
            list_concat(&head, &r->rq_head);
238
            n = r->n;
239
            r->n = 0;
240
            spinlock_unlock(&r->lock);
241
 
242
            /* append rq[i + 1] to rq[i] */
15 jermar 243
            r = &CPU->rq[i];
1 jermar 244
            spinlock_lock(&r->lock);
245
            list_concat(&r->rq_head, &head);
246
            r->n += n;
247
            spinlock_unlock(&r->lock);
248
        }
15 jermar 249
        CPU->needs_relink = 0;
1 jermar 250
    }
15 jermar 251
    spinlock_unlock(&CPU->lock);               
1 jermar 252
 
253
}
254
 
107 decky 255
 
256
/** Scheduler stack switch wrapper
257
 *
258
 * Second part of the scheduler() function
259
 * using new stack. Handling the actual context
260
 * switch to a new thread.
261
 *
262
 */
452 decky 263
static void scheduler_separated_stack(void)
1 jermar 264
{
265
    int priority;
266
 
227 jermar 267
    ASSERT(CPU != NULL);
268
 
15 jermar 269
    if (THREAD) {
270
        switch (THREAD->state) {
1 jermar 271
            case Running:
125 jermar 272
            THREAD->state = Ready;
273
            spinlock_unlock(&THREAD->lock);
274
            thread_ready(THREAD);
275
            break;
1 jermar 276
 
277
            case Exiting:
125 jermar 278
            frame_free((__address) THREAD->kstack);
279
            if (THREAD->ustack) {
280
                frame_free((__address) THREAD->ustack);
281
            }
1 jermar 282
 
125 jermar 283
            /*
284
             * Detach from the containing task.
285
             */
286
            spinlock_lock(&TASK->lock);
287
            list_remove(&THREAD->th_link);
288
            spinlock_unlock(&TASK->lock);
73 vana 289
 
125 jermar 290
            spinlock_unlock(&THREAD->lock);
291
 
292
            spinlock_lock(&threads_lock);
293
            list_remove(&THREAD->threads_link);
294
            spinlock_unlock(&threads_lock);
73 vana 295
 
125 jermar 296
            spinlock_lock(&CPU->lock);
650 jermar 297
            if(CPU->fpu_owner==THREAD)
298
                CPU->fpu_owner=NULL;
125 jermar 299
            spinlock_unlock(&CPU->lock);
300
 
301
            free(THREAD);
302
 
303
            break;
304
 
1 jermar 305
            case Sleeping:
125 jermar 306
            /*
307
             * Prefer the thread after it's woken up.
308
             */
413 jermar 309
            THREAD->priority = -1;
1 jermar 310
 
125 jermar 311
            /*
312
             * We need to release wq->lock which we locked in waitq_sleep().
313
             * Address of wq->lock is kept in THREAD->sleep_queue.
314
             */
315
            spinlock_unlock(&THREAD->sleep_queue->lock);
1 jermar 316
 
125 jermar 317
            /*
318
             * Check for possible requests for out-of-context invocation.
319
             */
320
            if (THREAD->call_me) {
321
                THREAD->call_me(THREAD->call_me_with);
322
                THREAD->call_me = NULL;
323
                THREAD->call_me_with = NULL;
324
            }
1 jermar 325
 
125 jermar 326
            spinlock_unlock(&THREAD->lock);
1 jermar 327
 
125 jermar 328
            break;
329
 
1 jermar 330
            default:
125 jermar 331
            /*
332
             * Entering state is unexpected.
333
             */
334
            panic("tid%d: unexpected state %s\n", THREAD->tid, thread_states[THREAD->state]);
335
            break;
1 jermar 336
        }
15 jermar 337
        THREAD = NULL;
1 jermar 338
    }
198 jermar 339
 
214 vana 340
 
15 jermar 341
    THREAD = find_best_thread();
1 jermar 342
 
15 jermar 343
    spinlock_lock(&THREAD->lock);
413 jermar 344
    priority = THREAD->priority;
15 jermar 345
    spinlock_unlock(&THREAD->lock);
192 jermar 346
 
1 jermar 347
    relink_rq(priority);       
348
 
15 jermar 349
    spinlock_lock(&THREAD->lock);  
1 jermar 350
 
351
    /*
352
     * If both the old and the new task are the same, lots of work is avoided.
353
     */
15 jermar 354
    if (TASK != THREAD->task) {
703 jermar 355
        as_t *as1 = NULL;
356
        as_t *as2;
1 jermar 357
 
15 jermar 358
        if (TASK) {
359
            spinlock_lock(&TASK->lock);
703 jermar 360
            as1 = TASK->as;
15 jermar 361
            spinlock_unlock(&TASK->lock);
1 jermar 362
        }
363
 
15 jermar 364
        spinlock_lock(&THREAD->task->lock);
703 jermar 365
        as2 = THREAD->task->as;
15 jermar 366
        spinlock_unlock(&THREAD->task->lock);
1 jermar 367
 
368
        /*
703 jermar 369
         * Note that it is possible for two tasks to share one address space.
1 jermar 370
         */
703 jermar 371
        if (as1 != as2) {
1 jermar 372
            /*
703 jermar 373
             * Both tasks and address spaces are different.
1 jermar 374
             * Replace the old one with the new one.
375
             */
703 jermar 376
            as_install(as2);
1 jermar 377
        }
15 jermar 378
        TASK = THREAD->task;   
1 jermar 379
    }
380
 
15 jermar 381
    THREAD->state = Running;
1 jermar 382
 
383
    #ifdef SCHEDULER_VERBOSE
413 jermar 384
    printf("cpu%d: tid %d (priority=%d,ticks=%d,nrdy=%d)\n", CPU->id, THREAD->tid, THREAD->priority, THREAD->ticks, CPU->nrdy);
1 jermar 385
    #endif  
386
 
213 jermar 387
    /*
388
     * Copy the knowledge of CPU, TASK, THREAD and preemption counter to thread's stack.
389
     */
184 jermar 390
    the_copy(THE, (the_t *) THREAD->kstack);
391
 
15 jermar 392
    context_restore(&THREAD->saved_context);
1 jermar 393
    /* not reached */
394
}
395
 
107 decky 396
 
452 decky 397
/** The scheduler
398
 *
399
 * The thread scheduling procedure.
675 jermar 400
 * Passes control directly to
401
 * scheduler_separated_stack().
452 decky 402
 *
403
 */
404
void scheduler(void)
405
{
406
    volatile ipl_t ipl;
407
 
408
    ASSERT(CPU != NULL);
409
 
410
    ipl = interrupts_disable();
411
 
631 palkovsky 412
    if (atomic_get(&haltstate))
452 decky 413
        halt();
414
 
415
    if (THREAD) {
416
        spinlock_lock(&THREAD->lock);
458 decky 417
#ifndef CONFIG_FPU_LAZY
452 decky 418
        fpu_context_save(&(THREAD->saved_fpu_context));
419
#endif
420
        if (!context_save(&THREAD->saved_context)) {
421
            /*
422
             * This is the place where threads leave scheduler();
423
             */
424
            before_thread_runs();
425
            spinlock_unlock(&THREAD->lock);
426
            interrupts_restore(THREAD->saved_context.ipl);
427
            return;
428
        }
429
 
430
        /*
431
         * Interrupt priority level of preempted thread is recorded here
432
         * to facilitate scheduler() invocations from interrupts_disable()'d
433
         * code (e.g. waitq_sleep_timeout()).
434
         */
435
        THREAD->saved_context.ipl = ipl;
436
    }
437
 
438
    /*
557 jermar 439
     * Through the 'THE' structure, we keep track of THREAD, TASK, CPU, VM
452 decky 440
     * and preemption counter. At this point THE could be coming either
441
     * from THREAD's or CPU's stack.
442
     */
443
    the_copy(THE, (the_t *) CPU->stack);
444
 
445
    /*
446
     * We may not keep the old stack.
447
     * Reason: If we kept the old stack and got blocked, for instance, in
448
     * find_best_thread(), the old thread could get rescheduled by another
449
     * CPU and overwrite the part of its own stack that was also used by
450
     * the scheduler on this CPU.
451
     *
452
     * Moreover, we have to bypass the compiler-generated POP sequence
453
     * which is fooled by SP being set to the very top of the stack.
454
     * Therefore the scheduler() function continues in
455
     * scheduler_separated_stack().
456
     */
457
    context_save(&CPU->saved_context);
458
    context_set(&CPU->saved_context, FADDR(scheduler_separated_stack), (__address) CPU->stack, CPU_STACK_SIZE);
459
    context_restore(&CPU->saved_context);
460
    /* not reached */
461
}
462
 
463
 
464
 
465
 
466
 
458 decky 467
#ifdef CONFIG_SMP
107 decky 468
/** Load balancing thread
469
 *
470
 * SMP load balancing thread, supervising thread supplies
471
 * for the CPU it's wired to.
472
 *
473
 * @param arg Generic thread argument (unused).
474
 *
1 jermar 475
 */
476
void kcpulb(void *arg)
477
{
478
    thread_t *t;
479
    int count, i, j, k = 0;
413 jermar 480
    ipl_t ipl;
1 jermar 481
 
482
loop:
483
    /*
484
     * Sleep until there's some work to do.
485
     */
15 jermar 486
    waitq_sleep(&CPU->kcpulb_wq);
1 jermar 487
 
488
not_satisfied:
489
    /*
490
     * Calculate the number of threads that will be migrated/stolen from
491
     * other CPU's. Note that situation can have changed between two
492
     * passes. Each time get the most up to date counts.
493
     */
413 jermar 494
    ipl = interrupts_disable();
15 jermar 495
    spinlock_lock(&CPU->lock);
625 palkovsky 496
    count = atomic_get(&nrdy) / config.cpu_active;
15 jermar 497
    count -= CPU->nrdy;
498
    spinlock_unlock(&CPU->lock);
413 jermar 499
    interrupts_restore(ipl);
1 jermar 500
 
501
    if (count <= 0)
502
        goto satisfied;
503
 
504
    /*
505
     * Searching least priority queues on all CPU's first and most priority queues on all CPU's last.
506
     */
507
    for (j=RQ_COUNT-1; j >= 0; j--) {
508
        for (i=0; i < config.cpu_active; i++) {
509
            link_t *l;
510
            runq_t *r;
511
            cpu_t *cpu;
512
 
513
            cpu = &cpus[(i + k) % config.cpu_active];
514
 
515
            /*
516
             * Not interested in ourselves.
517
             * Doesn't require interrupt disabling for kcpulb is X_WIRED.
518
             */
15 jermar 519
            if (CPU == cpu)
115 jermar 520
                continue;              
1 jermar 521
 
413 jermar 522
restart:        ipl = interrupts_disable();
115 jermar 523
            r = &cpu->rq[j];
1 jermar 524
            spinlock_lock(&r->lock);
525
            if (r->n == 0) {
526
                spinlock_unlock(&r->lock);
413 jermar 527
                interrupts_restore(ipl);
1 jermar 528
                continue;
529
            }
530
 
531
            t = NULL;
532
            l = r->rq_head.prev;    /* search rq from the back */
533
            while (l != &r->rq_head) {
534
                t = list_get_instance(l, thread_t, rq_link);
535
                /*
125 jermar 536
                 * We don't want to steal CPU-wired threads neither threads already stolen.
1 jermar 537
                 * The latter prevents threads from migrating between CPU's without ever being run.
125 jermar 538
                 * We don't want to steal threads whose FPU context is still in CPU.
73 vana 539
                 */
1 jermar 540
                spinlock_lock(&t->lock);
73 vana 541
                if ( (!(t->flags & (X_WIRED | X_STOLEN))) && (!(t->fpu_context_engaged)) ) {
115 jermar 542
 
1 jermar 543
                    /*
544
                     * Remove t from r.
545
                     */
546
 
547
                    spinlock_unlock(&t->lock);
548
 
549
                    /*
550
                     * Here we have to avoid deadlock with relink_rq(),
551
                     * because it locks cpu and r in a different order than we do.
552
                     */
553
                    if (!spinlock_trylock(&cpu->lock)) {
554
                        /* Release all locks and try again. */
555
                        spinlock_unlock(&r->lock);
413 jermar 556
                        interrupts_restore(ipl);
1 jermar 557
                        goto restart;
558
                    }
559
                    cpu->nrdy--;
560
                    spinlock_unlock(&cpu->lock);
561
 
475 jermar 562
                    atomic_dec(&nrdy);
1 jermar 563
 
125 jermar 564
                    r->n--;
1 jermar 565
                    list_remove(&t->rq_link);
566
 
567
                    break;
568
                }
569
                spinlock_unlock(&t->lock);
570
                l = l->prev;
571
                t = NULL;
572
            }
573
            spinlock_unlock(&r->lock);
574
 
575
            if (t) {
576
                /*
577
                 * Ready t on local CPU
578
                 */
579
                spinlock_lock(&t->lock);
580
                #ifdef KCPULB_VERBOSE
15 jermar 581
                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 582
                #endif
583
                t->flags |= X_STOLEN;
584
                spinlock_unlock(&t->lock);
585
 
586
                thread_ready(t);
587
 
413 jermar 588
                interrupts_restore(ipl);
1 jermar 589
 
590
                if (--count == 0)
591
                    goto satisfied;
592
 
593
                /*
125 jermar 594
                 * We are not satisfied yet, focus on another CPU next time.
1 jermar 595
                 */
596
                k++;
597
 
598
                continue;
599
            }
413 jermar 600
            interrupts_restore(ipl);
1 jermar 601
        }
602
    }
603
 
15 jermar 604
    if (CPU->nrdy) {
1 jermar 605
        /*
606
         * Be a little bit light-weight and let migrated threads run.
607
         */
608
        scheduler();
609
    }
610
    else {
611
        /*
612
         * We failed to migrate a single thread.
613
         * Something more sophisticated should be done.
614
         */
615
        scheduler();
616
    }
617
 
618
    goto not_satisfied;
125 jermar 619
 
1 jermar 620
satisfied:
621
    /*
622
     * Tell find_best_thread() to wake us up later again.
623
     */
625 palkovsky 624
    atomic_set(&CPU->kcpulbstarted,0);
1 jermar 625
    goto loop;
626
}
627
 
458 decky 628
#endif /* CONFIG_SMP */