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