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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>
1 jermar 35
#include <mm/vm.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);
297
            if(CPU->fpu_owner==THREAD) CPU->fpu_owner=NULL;
298
            spinlock_unlock(&CPU->lock);
299
 
300
            free(THREAD);
301
 
302
            break;
303
 
1 jermar 304
            case Sleeping:
125 jermar 305
            /*
306
             * Prefer the thread after it's woken up.
307
             */
413 jermar 308
            THREAD->priority = -1;
1 jermar 309
 
125 jermar 310
            /*
311
             * We need to release wq->lock which we locked in waitq_sleep().
312
             * Address of wq->lock is kept in THREAD->sleep_queue.
313
             */
314
            spinlock_unlock(&THREAD->sleep_queue->lock);
1 jermar 315
 
125 jermar 316
            /*
317
             * Check for possible requests for out-of-context invocation.
318
             */
319
            if (THREAD->call_me) {
320
                THREAD->call_me(THREAD->call_me_with);
321
                THREAD->call_me = NULL;
322
                THREAD->call_me_with = NULL;
323
            }
1 jermar 324
 
125 jermar 325
            spinlock_unlock(&THREAD->lock);
1 jermar 326
 
125 jermar 327
            break;
328
 
1 jermar 329
            default:
125 jermar 330
            /*
331
             * Entering state is unexpected.
332
             */
333
            panic("tid%d: unexpected state %s\n", THREAD->tid, thread_states[THREAD->state]);
334
            break;
1 jermar 335
        }
15 jermar 336
        THREAD = NULL;
1 jermar 337
    }
198 jermar 338
 
214 vana 339
 
15 jermar 340
    THREAD = find_best_thread();
1 jermar 341
 
15 jermar 342
    spinlock_lock(&THREAD->lock);
413 jermar 343
    priority = THREAD->priority;
15 jermar 344
    spinlock_unlock(&THREAD->lock);
192 jermar 345
 
1 jermar 346
    relink_rq(priority);       
347
 
15 jermar 348
    spinlock_lock(&THREAD->lock);  
1 jermar 349
 
350
    /*
351
     * If both the old and the new task are the same, lots of work is avoided.
352
     */
15 jermar 353
    if (TASK != THREAD->task) {
1 jermar 354
        vm_t *m1 = NULL;
355
        vm_t *m2;
356
 
15 jermar 357
        if (TASK) {
358
            spinlock_lock(&TASK->lock);
359
            m1 = TASK->vm;
360
            spinlock_unlock(&TASK->lock);
1 jermar 361
        }
362
 
15 jermar 363
        spinlock_lock(&THREAD->task->lock);
364
        m2 = THREAD->task->vm;
365
        spinlock_unlock(&THREAD->task->lock);
1 jermar 366
 
367
        /*
368
         * Note that it is possible for two tasks to share one vm mapping.
369
         */
370
        if (m1 != m2) {
371
            /*
372
             * Both tasks and vm mappings are different.
373
             * Replace the old one with the new one.
374
             */
375
            vm_install(m2);
376
        }
15 jermar 377
        TASK = THREAD->task;   
1 jermar 378
    }
379
 
15 jermar 380
    THREAD->state = Running;
1 jermar 381
 
382
    #ifdef SCHEDULER_VERBOSE
413 jermar 383
    printf("cpu%d: tid %d (priority=%d,ticks=%d,nrdy=%d)\n", CPU->id, THREAD->tid, THREAD->priority, THREAD->ticks, CPU->nrdy);
1 jermar 384
    #endif  
385
 
213 jermar 386
    /*
387
     * Copy the knowledge of CPU, TASK, THREAD and preemption counter to thread's stack.
388
     */
184 jermar 389
    the_copy(THE, (the_t *) THREAD->kstack);
390
 
15 jermar 391
    context_restore(&THREAD->saved_context);
1 jermar 392
    /* not reached */
393
}
394
 
107 decky 395
 
452 decky 396
/** The scheduler
397
 *
398
 * The thread scheduling procedure.
399
 *
400
 */
401
void scheduler(void)
402
{
403
    volatile ipl_t ipl;
404
 
405
    ASSERT(CPU != NULL);
406
 
407
    ipl = interrupts_disable();
408
 
409
    if (haltstate)
410
        halt();
411
 
412
    if (THREAD) {
413
        spinlock_lock(&THREAD->lock);
458 decky 414
#ifndef CONFIG_FPU_LAZY
452 decky 415
        fpu_context_save(&(THREAD->saved_fpu_context));
416
#endif
417
        if (!context_save(&THREAD->saved_context)) {
418
            /*
419
             * This is the place where threads leave scheduler();
420
             */
421
            before_thread_runs();
422
            spinlock_unlock(&THREAD->lock);
423
            interrupts_restore(THREAD->saved_context.ipl);
424
            return;
425
        }
426
 
427
        /*
428
         * Interrupt priority level of preempted thread is recorded here
429
         * to facilitate scheduler() invocations from interrupts_disable()'d
430
         * code (e.g. waitq_sleep_timeout()).
431
         */
432
        THREAD->saved_context.ipl = ipl;
433
    }
434
 
435
    /*
557 jermar 436
     * Through the 'THE' structure, we keep track of THREAD, TASK, CPU, VM
452 decky 437
     * and preemption counter. At this point THE could be coming either
438
     * from THREAD's or CPU's stack.
439
     */
440
    the_copy(THE, (the_t *) CPU->stack);
441
 
442
    /*
443
     * We may not keep the old stack.
444
     * Reason: If we kept the old stack and got blocked, for instance, in
445
     * find_best_thread(), the old thread could get rescheduled by another
446
     * CPU and overwrite the part of its own stack that was also used by
447
     * the scheduler on this CPU.
448
     *
449
     * Moreover, we have to bypass the compiler-generated POP sequence
450
     * which is fooled by SP being set to the very top of the stack.
451
     * Therefore the scheduler() function continues in
452
     * scheduler_separated_stack().
453
     */
454
    context_save(&CPU->saved_context);
455
    context_set(&CPU->saved_context, FADDR(scheduler_separated_stack), (__address) CPU->stack, CPU_STACK_SIZE);
456
    context_restore(&CPU->saved_context);
457
    /* not reached */
458
}
459
 
460
 
461
 
462
 
463
 
458 decky 464
#ifdef CONFIG_SMP
107 decky 465
/** Load balancing thread
466
 *
467
 * SMP load balancing thread, supervising thread supplies
468
 * for the CPU it's wired to.
469
 *
470
 * @param arg Generic thread argument (unused).
471
 *
1 jermar 472
 */
473
void kcpulb(void *arg)
474
{
475
    thread_t *t;
476
    int count, i, j, k = 0;
413 jermar 477
    ipl_t ipl;
1 jermar 478
 
479
loop:
480
    /*
481
     * Sleep until there's some work to do.
482
     */
15 jermar 483
    waitq_sleep(&CPU->kcpulb_wq);
1 jermar 484
 
485
not_satisfied:
486
    /*
487
     * Calculate the number of threads that will be migrated/stolen from
488
     * other CPU's. Note that situation can have changed between two
489
     * passes. Each time get the most up to date counts.
490
     */
413 jermar 491
    ipl = interrupts_disable();
15 jermar 492
    spinlock_lock(&CPU->lock);
1 jermar 493
    count = nrdy / config.cpu_active;
15 jermar 494
    count -= CPU->nrdy;
495
    spinlock_unlock(&CPU->lock);
413 jermar 496
    interrupts_restore(ipl);
1 jermar 497
 
498
    if (count <= 0)
499
        goto satisfied;
500
 
501
    /*
502
     * Searching least priority queues on all CPU's first and most priority queues on all CPU's last.
503
     */
504
    for (j=RQ_COUNT-1; j >= 0; j--) {
505
        for (i=0; i < config.cpu_active; i++) {
506
            link_t *l;
507
            runq_t *r;
508
            cpu_t *cpu;
509
 
510
            cpu = &cpus[(i + k) % config.cpu_active];
511
 
512
            /*
513
             * Not interested in ourselves.
514
             * Doesn't require interrupt disabling for kcpulb is X_WIRED.
515
             */
15 jermar 516
            if (CPU == cpu)
115 jermar 517
                continue;              
1 jermar 518
 
413 jermar 519
restart:        ipl = interrupts_disable();
115 jermar 520
            r = &cpu->rq[j];
1 jermar 521
            spinlock_lock(&r->lock);
522
            if (r->n == 0) {
523
                spinlock_unlock(&r->lock);
413 jermar 524
                interrupts_restore(ipl);
1 jermar 525
                continue;
526
            }
527
 
528
            t = NULL;
529
            l = r->rq_head.prev;    /* search rq from the back */
530
            while (l != &r->rq_head) {
531
                t = list_get_instance(l, thread_t, rq_link);
532
                /*
125 jermar 533
                 * We don't want to steal CPU-wired threads neither threads already stolen.
1 jermar 534
                 * The latter prevents threads from migrating between CPU's without ever being run.
125 jermar 535
                 * We don't want to steal threads whose FPU context is still in CPU.
73 vana 536
                 */
1 jermar 537
                spinlock_lock(&t->lock);
73 vana 538
                if ( (!(t->flags & (X_WIRED | X_STOLEN))) && (!(t->fpu_context_engaged)) ) {
115 jermar 539
 
1 jermar 540
                    /*
541
                     * Remove t from r.
542
                     */
543
 
544
                    spinlock_unlock(&t->lock);
545
 
546
                    /*
547
                     * Here we have to avoid deadlock with relink_rq(),
548
                     * because it locks cpu and r in a different order than we do.
549
                     */
550
                    if (!spinlock_trylock(&cpu->lock)) {
551
                        /* Release all locks and try again. */
552
                        spinlock_unlock(&r->lock);
413 jermar 553
                        interrupts_restore(ipl);
1 jermar 554
                        goto restart;
555
                    }
556
                    cpu->nrdy--;
557
                    spinlock_unlock(&cpu->lock);
558
 
475 jermar 559
                    atomic_dec(&nrdy);
1 jermar 560
 
125 jermar 561
                    r->n--;
1 jermar 562
                    list_remove(&t->rq_link);
563
 
564
                    break;
565
                }
566
                spinlock_unlock(&t->lock);
567
                l = l->prev;
568
                t = NULL;
569
            }
570
            spinlock_unlock(&r->lock);
571
 
572
            if (t) {
573
                /*
574
                 * Ready t on local CPU
575
                 */
576
                spinlock_lock(&t->lock);
577
                #ifdef KCPULB_VERBOSE
15 jermar 578
                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 579
                #endif
580
                t->flags |= X_STOLEN;
581
                spinlock_unlock(&t->lock);
582
 
583
                thread_ready(t);
584
 
413 jermar 585
                interrupts_restore(ipl);
1 jermar 586
 
587
                if (--count == 0)
588
                    goto satisfied;
589
 
590
                /*
125 jermar 591
                 * We are not satisfied yet, focus on another CPU next time.
1 jermar 592
                 */
593
                k++;
594
 
595
                continue;
596
            }
413 jermar 597
            interrupts_restore(ipl);
1 jermar 598
        }
599
    }
600
 
15 jermar 601
    if (CPU->nrdy) {
1 jermar 602
        /*
603
         * Be a little bit light-weight and let migrated threads run.
604
         */
605
        scheduler();
606
    }
607
    else {
608
        /*
609
         * We failed to migrate a single thread.
610
         * Something more sophisticated should be done.
611
         */
612
        scheduler();
613
    }
614
 
615
    goto not_satisfied;
125 jermar 616
 
1 jermar 617
satisfied:
618
    /*
619
     * Tell find_best_thread() to wake us up later again.
620
     */
15 jermar 621
    CPU->kcpulbstarted = 0;
1 jermar 622
    goto loop;
623
}
624
 
458 decky 625
#endif /* CONFIG_SMP */