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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
 
227 jermar 51
volatile count_t nrdy;
195 vana 52
 
1 jermar 53
 
118 jermar 54
/** Take actions before new thread runs
107 decky 55
 *
118 jermar 56
 * Perform actions that need to be
57
 * taken before the newly selected
58
 * tread is passed control.
107 decky 59
 *
60
 */
52 vana 61
void before_thread_runs(void)
62
{
309 palkovsky 63
    before_thread_runs_arch();
64
#ifdef FPU_LAZY
65
    if(THREAD==CPU->fpu_owner)
66
        fpu_enable();
67
    else
68
        fpu_disable();
69
#else
70
    fpu_enable();
71
    if (THREAD->fpu_context_exists)
72
        fpu_context_restore(&(THREAD->saved_fpu_context));
73
    else {
74
        fpu_init();
75
        THREAD->fpu_context_exists=1;
76
    }
77
#endif
52 vana 78
}
79
 
309 palkovsky 80
#ifdef FPU_LAZY
81
void scheduler_fpu_lazy_request(void)
82
{
83
    fpu_enable();
84
    if (CPU->fpu_owner != NULL) {  
85
        fpu_context_save(&CPU->fpu_owner->saved_fpu_context);
86
        /* don't prevent migration */
87
        CPU->fpu_owner->fpu_context_engaged=0;
88
    }
89
    if (THREAD->fpu_context_exists)
90
        fpu_context_restore(&THREAD->saved_fpu_context);
91
    else {
92
        fpu_init();
93
        THREAD->fpu_context_exists=1;
94
    }
95
    CPU->fpu_owner=THREAD;
96
    THREAD->fpu_context_engaged = 1;
97
}
98
#endif
52 vana 99
 
107 decky 100
/** Initialize scheduler
101
 *
102
 * Initialize kernel scheduler.
103
 *
104
 */
1 jermar 105
void scheduler_init(void)
106
{
107
}
108
 
107 decky 109
 
110
/** Get thread to be scheduled
111
 *
112
 * Get the optimal thread to be scheduled
109 jermar 113
 * according to thread accounting and scheduler
107 decky 114
 * policy.
115
 *
116
 * @return Thread to be scheduled.
117
 *
118
 */
1 jermar 119
struct thread *find_best_thread(void)
120
{
121
    thread_t *t;
122
    runq_t *r;
123
    int i, n;
124
 
227 jermar 125
    ASSERT(CPU != NULL);
126
 
1 jermar 127
loop:
413 jermar 128
    interrupts_disable();
1 jermar 129
 
15 jermar 130
    spinlock_lock(&CPU->lock);
131
    n = CPU->nrdy;
132
    spinlock_unlock(&CPU->lock);
1 jermar 133
 
413 jermar 134
    interrupts_enable();
1 jermar 135
 
136
    if (n == 0) {
137
        #ifdef __SMP__
138
        /*
139
         * If the load balancing thread is not running, wake it up and
140
         * set CPU-private flag that the kcpulb has been started.
141
         */
15 jermar 142
        if (test_and_set(&CPU->kcpulbstarted) == 0) {
125 jermar 143
            waitq_wakeup(&CPU->kcpulb_wq, 0);
1 jermar 144
            goto loop;
145
        }
146
        #endif /* __SMP__ */
147
 
148
        /*
149
         * For there was nothing to run, the CPU goes to sleep
150
         * until a hardware interrupt or an IPI comes.
151
         * This improves energy saving and hyperthreading.
152
         * On the other hand, several hardware interrupts can be ignored.
153
         */
154
         cpu_sleep();
155
         goto loop;
156
    }
157
 
413 jermar 158
    interrupts_disable();
114 jermar 159
 
160
    i = 0;
161
retry:
162
    for (; i<RQ_COUNT; i++) {
15 jermar 163
        r = &CPU->rq[i];
1 jermar 164
        spinlock_lock(&r->lock);
165
        if (r->n == 0) {
166
            /*
167
             * If this queue is empty, try a lower-priority queue.
168
             */
169
            spinlock_unlock(&r->lock);
170
            continue;
171
        }
213 jermar 172
 
115 jermar 173
        /* avoid deadlock with relink_rq() */
114 jermar 174
        if (!spinlock_trylock(&CPU->lock)) {
175
            /*
176
             * Unlock r and try again.
177
             */
178
            spinlock_unlock(&r->lock);
179
            goto retry;
180
        }
15 jermar 181
        CPU->nrdy--;
182
        spinlock_unlock(&CPU->lock);
1 jermar 183
 
248 jermar 184
        atomic_dec((int *) &nrdy);
1 jermar 185
        r->n--;
186
 
187
        /*
188
         * Take the first thread from the queue.
189
         */
190
        t = list_get_instance(r->rq_head.next, thread_t, rq_link);
191
        list_remove(&t->rq_link);
192
 
193
        spinlock_unlock(&r->lock);
194
 
195
        spinlock_lock(&t->lock);
15 jermar 196
        t->cpu = CPU;
1 jermar 197
 
198
        t->ticks = us2ticks((i+1)*10000);
413 jermar 199
        t->priority = i;    /* eventually correct rq index */
1 jermar 200
 
201
        /*
202
         * Clear the X_STOLEN flag so that t can be migrated when load balancing needs emerge.
203
         */
204
        t->flags &= ~X_STOLEN;
205
        spinlock_unlock(&t->lock);
206
 
207
        return t;
208
    }
209
    goto loop;
210
 
211
}
212
 
107 decky 213
 
214
/** Prevent rq starvation
215
 *
216
 * Prevent low priority threads from starving in rq's.
217
 *
218
 * When the function decides to relink rq's, it reconnects
219
 * respective pointers so that in result threads with 'pri'
220
 * greater or equal 'start' are moved to a higher-priority queue.
221
 *
222
 * @param start Threshold priority.
223
 *
1 jermar 224
 */
225
void relink_rq(int start)
226
{
227
    link_t head;
228
    runq_t *r;
229
    int i, n;
230
 
231
    list_initialize(&head);
15 jermar 232
    spinlock_lock(&CPU->lock);
233
    if (CPU->needs_relink > NEEDS_RELINK_MAX) {
1 jermar 234
        for (i = start; i<RQ_COUNT-1; i++) {
235
            /* remember and empty rq[i + 1] */
15 jermar 236
            r = &CPU->rq[i + 1];
1 jermar 237
            spinlock_lock(&r->lock);
238
            list_concat(&head, &r->rq_head);
239
            n = r->n;
240
            r->n = 0;
241
            spinlock_unlock(&r->lock);
242
 
243
            /* append rq[i + 1] to rq[i] */
15 jermar 244
            r = &CPU->rq[i];
1 jermar 245
            spinlock_lock(&r->lock);
246
            list_concat(&r->rq_head, &head);
247
            r->n += n;
248
            spinlock_unlock(&r->lock);
249
        }
15 jermar 250
        CPU->needs_relink = 0;
1 jermar 251
    }
15 jermar 252
    spinlock_unlock(&CPU->lock);               
1 jermar 253
 
254
}
255
 
107 decky 256
 
257
/** The scheduler
258
 *
259
 * The thread scheduling procedure.
260
 *
1 jermar 261
 */
262
void scheduler(void)
263
{
413 jermar 264
    volatile ipl_t ipl;
1 jermar 265
 
227 jermar 266
    ASSERT(CPU != NULL);
267
 
413 jermar 268
    ipl = interrupts_disable();
1 jermar 269
 
270
    if (haltstate)
271
        halt();
272
 
15 jermar 273
    if (THREAD) {
274
        spinlock_lock(&THREAD->lock);
309 palkovsky 275
#ifndef FPU_LAZY
57 vana 276
        fpu_context_save(&(THREAD->saved_fpu_context));
309 palkovsky 277
#endif
15 jermar 278
        if (!context_save(&THREAD->saved_context)) {
1 jermar 279
            /*
280
             * This is the place where threads leave scheduler();
281
             */
22 jermar 282
            before_thread_runs();
125 jermar 283
            spinlock_unlock(&THREAD->lock);
413 jermar 284
            interrupts_restore(THREAD->saved_context.ipl);
1 jermar 285
            return;
286
        }
170 jermar 287
 
288
        /*
413 jermar 289
         * Interrupt priority level of preempted thread is recorded here
290
         * to facilitate scheduler() invocations from interrupts_disable()'d
291
         * code (e.g. waitq_sleep_timeout()).
170 jermar 292
         */
413 jermar 293
        THREAD->saved_context.ipl = ipl;
1 jermar 294
    }
295
 
296
    /*
184 jermar 297
     * Through the 'THE' structure, we keep track of THREAD, TASK, CPU
298
     * and preemption counter. At this point THE could be coming either
299
     * from THREAD's or CPU's stack.
300
     */
301
    the_copy(THE, (the_t *) CPU->stack);
302
 
303
    /*
1 jermar 304
     * We may not keep the old stack.
305
     * Reason: If we kept the old stack and got blocked, for instance, in
306
     * find_best_thread(), the old thread could get rescheduled by another
307
     * CPU and overwrite the part of its own stack that was also used by
308
     * the scheduler on this CPU.
309
     *
310
     * Moreover, we have to bypass the compiler-generated POP sequence
311
     * which is fooled by SP being set to the very top of the stack.
312
     * Therefore the scheduler() function continues in
313
     * scheduler_separated_stack().
314
     */
15 jermar 315
    context_save(&CPU->saved_context);
97 jermar 316
    context_set(&CPU->saved_context, FADDR(scheduler_separated_stack), CPU->stack, CPU_STACK_SIZE);
15 jermar 317
    context_restore(&CPU->saved_context);
1 jermar 318
    /* not reached */
319
}
320
 
107 decky 321
 
322
/** Scheduler stack switch wrapper
323
 *
324
 * Second part of the scheduler() function
325
 * using new stack. Handling the actual context
326
 * switch to a new thread.
327
 *
328
 */
1 jermar 329
void scheduler_separated_stack(void)
330
{
331
    int priority;
332
 
227 jermar 333
    ASSERT(CPU != NULL);
334
 
15 jermar 335
    if (THREAD) {
336
        switch (THREAD->state) {
1 jermar 337
            case Running:
125 jermar 338
            THREAD->state = Ready;
339
            spinlock_unlock(&THREAD->lock);
340
            thread_ready(THREAD);
341
            break;
1 jermar 342
 
343
            case Exiting:
125 jermar 344
            frame_free((__address) THREAD->kstack);
345
            if (THREAD->ustack) {
346
                frame_free((__address) THREAD->ustack);
347
            }
1 jermar 348
 
125 jermar 349
            /*
350
             * Detach from the containing task.
351
             */
352
            spinlock_lock(&TASK->lock);
353
            list_remove(&THREAD->th_link);
354
            spinlock_unlock(&TASK->lock);
73 vana 355
 
125 jermar 356
            spinlock_unlock(&THREAD->lock);
357
 
358
            spinlock_lock(&threads_lock);
359
            list_remove(&THREAD->threads_link);
360
            spinlock_unlock(&threads_lock);
73 vana 361
 
125 jermar 362
            spinlock_lock(&CPU->lock);
363
            if(CPU->fpu_owner==THREAD) CPU->fpu_owner=NULL;
364
            spinlock_unlock(&CPU->lock);
365
 
366
            free(THREAD);
367
 
368
            break;
369
 
1 jermar 370
            case Sleeping:
125 jermar 371
            /*
372
             * Prefer the thread after it's woken up.
373
             */
413 jermar 374
            THREAD->priority = -1;
1 jermar 375
 
125 jermar 376
            /*
377
             * We need to release wq->lock which we locked in waitq_sleep().
378
             * Address of wq->lock is kept in THREAD->sleep_queue.
379
             */
380
            spinlock_unlock(&THREAD->sleep_queue->lock);
1 jermar 381
 
125 jermar 382
            /*
383
             * Check for possible requests for out-of-context invocation.
384
             */
385
            if (THREAD->call_me) {
386
                THREAD->call_me(THREAD->call_me_with);
387
                THREAD->call_me = NULL;
388
                THREAD->call_me_with = NULL;
389
            }
1 jermar 390
 
125 jermar 391
            spinlock_unlock(&THREAD->lock);
1 jermar 392
 
125 jermar 393
            break;
394
 
1 jermar 395
            default:
125 jermar 396
            /*
397
             * Entering state is unexpected.
398
             */
399
            panic("tid%d: unexpected state %s\n", THREAD->tid, thread_states[THREAD->state]);
400
            break;
1 jermar 401
        }
15 jermar 402
        THREAD = NULL;
1 jermar 403
    }
198 jermar 404
 
214 vana 405
 
15 jermar 406
    THREAD = find_best_thread();
1 jermar 407
 
15 jermar 408
    spinlock_lock(&THREAD->lock);
413 jermar 409
    priority = THREAD->priority;
15 jermar 410
    spinlock_unlock(&THREAD->lock);
192 jermar 411
 
1 jermar 412
    relink_rq(priority);       
413
 
15 jermar 414
    spinlock_lock(&THREAD->lock);  
1 jermar 415
 
416
    /*
417
     * If both the old and the new task are the same, lots of work is avoided.
418
     */
15 jermar 419
    if (TASK != THREAD->task) {
1 jermar 420
        vm_t *m1 = NULL;
421
        vm_t *m2;
422
 
15 jermar 423
        if (TASK) {
424
            spinlock_lock(&TASK->lock);
425
            m1 = TASK->vm;
426
            spinlock_unlock(&TASK->lock);
1 jermar 427
        }
428
 
15 jermar 429
        spinlock_lock(&THREAD->task->lock);
430
        m2 = THREAD->task->vm;
431
        spinlock_unlock(&THREAD->task->lock);
1 jermar 432
 
433
        /*
434
         * Note that it is possible for two tasks to share one vm mapping.
435
         */
436
        if (m1 != m2) {
437
            /*
438
             * Both tasks and vm mappings are different.
439
             * Replace the old one with the new one.
440
             */
441
            vm_install(m2);
442
        }
15 jermar 443
        TASK = THREAD->task;   
1 jermar 444
    }
445
 
15 jermar 446
    THREAD->state = Running;
1 jermar 447
 
448
    #ifdef SCHEDULER_VERBOSE
413 jermar 449
    printf("cpu%d: tid %d (priority=%d,ticks=%d,nrdy=%d)\n", CPU->id, THREAD->tid, THREAD->priority, THREAD->ticks, CPU->nrdy);
1 jermar 450
    #endif  
451
 
213 jermar 452
    /*
453
     * Copy the knowledge of CPU, TASK, THREAD and preemption counter to thread's stack.
454
     */
184 jermar 455
    the_copy(THE, (the_t *) THREAD->kstack);
456
 
15 jermar 457
    context_restore(&THREAD->saved_context);
1 jermar 458
    /* not reached */
459
}
460
 
107 decky 461
 
1 jermar 462
#ifdef __SMP__
107 decky 463
/** Load balancing thread
464
 *
465
 * SMP load balancing thread, supervising thread supplies
466
 * for the CPU it's wired to.
467
 *
468
 * @param arg Generic thread argument (unused).
469
 *
1 jermar 470
 */
471
void kcpulb(void *arg)
472
{
473
    thread_t *t;
474
    int count, i, j, k = 0;
413 jermar 475
    ipl_t ipl;
1 jermar 476
 
477
loop:
478
    /*
479
     * Sleep until there's some work to do.
480
     */
15 jermar 481
    waitq_sleep(&CPU->kcpulb_wq);
1 jermar 482
 
483
not_satisfied:
484
    /*
485
     * Calculate the number of threads that will be migrated/stolen from
486
     * other CPU's. Note that situation can have changed between two
487
     * passes. Each time get the most up to date counts.
488
     */
413 jermar 489
    ipl = interrupts_disable();
15 jermar 490
    spinlock_lock(&CPU->lock);
1 jermar 491
    count = nrdy / config.cpu_active;
15 jermar 492
    count -= CPU->nrdy;
493
    spinlock_unlock(&CPU->lock);
413 jermar 494
    interrupts_restore(ipl);
1 jermar 495
 
496
    if (count <= 0)
497
        goto satisfied;
498
 
499
    /*
500
     * Searching least priority queues on all CPU's first and most priority queues on all CPU's last.
501
     */
502
    for (j=RQ_COUNT-1; j >= 0; j--) {
503
        for (i=0; i < config.cpu_active; i++) {
504
            link_t *l;
505
            runq_t *r;
506
            cpu_t *cpu;
507
 
508
            cpu = &cpus[(i + k) % config.cpu_active];
509
 
510
            /*
511
             * Not interested in ourselves.
512
             * Doesn't require interrupt disabling for kcpulb is X_WIRED.
513
             */
15 jermar 514
            if (CPU == cpu)
115 jermar 515
                continue;              
1 jermar 516
 
413 jermar 517
restart:        ipl = interrupts_disable();
115 jermar 518
            r = &cpu->rq[j];
1 jermar 519
            spinlock_lock(&r->lock);
520
            if (r->n == 0) {
521
                spinlock_unlock(&r->lock);
413 jermar 522
                interrupts_restore(ipl);
1 jermar 523
                continue;
524
            }
525
 
526
            t = NULL;
527
            l = r->rq_head.prev;    /* search rq from the back */
528
            while (l != &r->rq_head) {
529
                t = list_get_instance(l, thread_t, rq_link);
530
                /*
125 jermar 531
                 * We don't want to steal CPU-wired threads neither threads already stolen.
1 jermar 532
                 * The latter prevents threads from migrating between CPU's without ever being run.
125 jermar 533
                 * We don't want to steal threads whose FPU context is still in CPU.
73 vana 534
                 */
1 jermar 535
                spinlock_lock(&t->lock);
73 vana 536
                if ( (!(t->flags & (X_WIRED | X_STOLEN))) && (!(t->fpu_context_engaged)) ) {
115 jermar 537
 
1 jermar 538
                    /*
539
                     * Remove t from r.
540
                     */
541
 
542
                    spinlock_unlock(&t->lock);
543
 
544
                    /*
545
                     * Here we have to avoid deadlock with relink_rq(),
546
                     * because it locks cpu and r in a different order than we do.
547
                     */
548
                    if (!spinlock_trylock(&cpu->lock)) {
549
                        /* Release all locks and try again. */
550
                        spinlock_unlock(&r->lock);
413 jermar 551
                        interrupts_restore(ipl);
1 jermar 552
                        goto restart;
553
                    }
554
                    cpu->nrdy--;
555
                    spinlock_unlock(&cpu->lock);
556
 
258 palkovsky 557
                    atomic_dec((int *)&nrdy);
1 jermar 558
 
125 jermar 559
                    r->n--;
1 jermar 560
                    list_remove(&t->rq_link);
561
 
562
                    break;
563
                }
564
                spinlock_unlock(&t->lock);
565
                l = l->prev;
566
                t = NULL;
567
            }
568
            spinlock_unlock(&r->lock);
569
 
570
            if (t) {
571
                /*
572
                 * Ready t on local CPU
573
                 */
574
                spinlock_lock(&t->lock);
575
                #ifdef KCPULB_VERBOSE
15 jermar 576
                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 577
                #endif
578
                t->flags |= X_STOLEN;
579
                spinlock_unlock(&t->lock);
580
 
581
                thread_ready(t);
582
 
413 jermar 583
                interrupts_restore(ipl);
1 jermar 584
 
585
                if (--count == 0)
586
                    goto satisfied;
587
 
588
                /*
125 jermar 589
                 * We are not satisfied yet, focus on another CPU next time.
1 jermar 590
                 */
591
                k++;
592
 
593
                continue;
594
            }
413 jermar 595
            interrupts_restore(ipl);
1 jermar 596
        }
597
    }
598
 
15 jermar 599
    if (CPU->nrdy) {
1 jermar 600
        /*
601
         * Be a little bit light-weight and let migrated threads run.
602
         */
603
        scheduler();
604
    }
605
    else {
606
        /*
607
         * We failed to migrate a single thread.
608
         * Something more sophisticated should be done.
609
         */
610
        scheduler();
611
    }
612
 
613
    goto not_satisfied;
125 jermar 614
 
1 jermar 615
satisfied:
616
    /*
617
     * Tell find_best_thread() to wake us up later again.
618
     */
15 jermar 619
    CPU->kcpulbstarted = 0;
1 jermar 620
    goto loop;
621
}
622
 
623
#endif /* __SMP__ */