Subversion Repositories HelenOS

Rev

Rev 430 | Rev 458 | 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>
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
 */
452 decky 119
static struct thread *find_best_thread(void)
1 jermar 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
 */
452 decky 225
static void relink_rq(int start)
1 jermar 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
/** Scheduler stack switch wrapper
258
 *
259
 * Second part of the scheduler() function
260
 * using new stack. Handling the actual context
261
 * switch to a new thread.
262
 *
263
 */
452 decky 264
static void scheduler_separated_stack(void)
1 jermar 265
{
266
    int priority;
267
 
227 jermar 268
    ASSERT(CPU != NULL);
269
 
15 jermar 270
    if (THREAD) {
271
        switch (THREAD->state) {
1 jermar 272
            case Running:
125 jermar 273
            THREAD->state = Ready;
274
            spinlock_unlock(&THREAD->lock);
275
            thread_ready(THREAD);
276
            break;
1 jermar 277
 
278
            case Exiting:
125 jermar 279
            frame_free((__address) THREAD->kstack);
280
            if (THREAD->ustack) {
281
                frame_free((__address) THREAD->ustack);
282
            }
1 jermar 283
 
125 jermar 284
            /*
285
             * Detach from the containing task.
286
             */
287
            spinlock_lock(&TASK->lock);
288
            list_remove(&THREAD->th_link);
289
            spinlock_unlock(&TASK->lock);
73 vana 290
 
125 jermar 291
            spinlock_unlock(&THREAD->lock);
292
 
293
            spinlock_lock(&threads_lock);
294
            list_remove(&THREAD->threads_link);
295
            spinlock_unlock(&threads_lock);
73 vana 296
 
125 jermar 297
            spinlock_lock(&CPU->lock);
298
            if(CPU->fpu_owner==THREAD) CPU->fpu_owner=NULL;
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) {
1 jermar 355
        vm_t *m1 = NULL;
356
        vm_t *m2;
357
 
15 jermar 358
        if (TASK) {
359
            spinlock_lock(&TASK->lock);
360
            m1 = TASK->vm;
361
            spinlock_unlock(&TASK->lock);
1 jermar 362
        }
363
 
15 jermar 364
        spinlock_lock(&THREAD->task->lock);
365
        m2 = THREAD->task->vm;
366
        spinlock_unlock(&THREAD->task->lock);
1 jermar 367
 
368
        /*
369
         * Note that it is possible for two tasks to share one vm mapping.
370
         */
371
        if (m1 != m2) {
372
            /*
373
             * Both tasks and vm mappings are different.
374
             * Replace the old one with the new one.
375
             */
376
            vm_install(m2);
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.
400
 *
401
 */
402
void scheduler(void)
403
{
404
    volatile ipl_t ipl;
405
 
406
    ASSERT(CPU != NULL);
407
 
408
    ipl = interrupts_disable();
409
 
410
    if (haltstate)
411
        halt();
412
 
413
    if (THREAD) {
414
        spinlock_lock(&THREAD->lock);
415
#ifndef FPU_LAZY
416
        fpu_context_save(&(THREAD->saved_fpu_context));
417
#endif
418
        if (!context_save(&THREAD->saved_context)) {
419
            /*
420
             * This is the place where threads leave scheduler();
421
             */
422
            before_thread_runs();
423
            spinlock_unlock(&THREAD->lock);
424
            interrupts_restore(THREAD->saved_context.ipl);
425
            return;
426
        }
427
 
428
        /*
429
         * Interrupt priority level of preempted thread is recorded here
430
         * to facilitate scheduler() invocations from interrupts_disable()'d
431
         * code (e.g. waitq_sleep_timeout()).
432
         */
433
        THREAD->saved_context.ipl = ipl;
434
    }
435
 
436
    /*
437
     * Through the 'THE' structure, we keep track of THREAD, TASK, CPU
438
     * and preemption counter. At this point THE could be coming either
439
     * from THREAD's or CPU's stack.
440
     */
441
    the_copy(THE, (the_t *) CPU->stack);
442
 
443
    /*
444
     * We may not keep the old stack.
445
     * Reason: If we kept the old stack and got blocked, for instance, in
446
     * find_best_thread(), the old thread could get rescheduled by another
447
     * CPU and overwrite the part of its own stack that was also used by
448
     * the scheduler on this CPU.
449
     *
450
     * Moreover, we have to bypass the compiler-generated POP sequence
451
     * which is fooled by SP being set to the very top of the stack.
452
     * Therefore the scheduler() function continues in
453
     * scheduler_separated_stack().
454
     */
455
    context_save(&CPU->saved_context);
456
    context_set(&CPU->saved_context, FADDR(scheduler_separated_stack), (__address) CPU->stack, CPU_STACK_SIZE);
457
    context_restore(&CPU->saved_context);
458
    /* not reached */
459
}
460
 
461
 
462
 
463
 
464
 
1 jermar 465
#ifdef __SMP__
107 decky 466
/** Load balancing thread
467
 *
468
 * SMP load balancing thread, supervising thread supplies
469
 * for the CPU it's wired to.
470
 *
471
 * @param arg Generic thread argument (unused).
472
 *
1 jermar 473
 */
474
void kcpulb(void *arg)
475
{
476
    thread_t *t;
477
    int count, i, j, k = 0;
413 jermar 478
    ipl_t ipl;
1 jermar 479
 
480
loop:
481
    /*
482
     * Sleep until there's some work to do.
483
     */
15 jermar 484
    waitq_sleep(&CPU->kcpulb_wq);
1 jermar 485
 
486
not_satisfied:
487
    /*
488
     * Calculate the number of threads that will be migrated/stolen from
489
     * other CPU's. Note that situation can have changed between two
490
     * passes. Each time get the most up to date counts.
491
     */
413 jermar 492
    ipl = interrupts_disable();
15 jermar 493
    spinlock_lock(&CPU->lock);
1 jermar 494
    count = nrdy / config.cpu_active;
15 jermar 495
    count -= CPU->nrdy;
496
    spinlock_unlock(&CPU->lock);
413 jermar 497
    interrupts_restore(ipl);
1 jermar 498
 
499
    if (count <= 0)
500
        goto satisfied;
501
 
502
    /*
503
     * Searching least priority queues on all CPU's first and most priority queues on all CPU's last.
504
     */
505
    for (j=RQ_COUNT-1; j >= 0; j--) {
506
        for (i=0; i < config.cpu_active; i++) {
507
            link_t *l;
508
            runq_t *r;
509
            cpu_t *cpu;
510
 
511
            cpu = &cpus[(i + k) % config.cpu_active];
512
 
513
            /*
514
             * Not interested in ourselves.
515
             * Doesn't require interrupt disabling for kcpulb is X_WIRED.
516
             */
15 jermar 517
            if (CPU == cpu)
115 jermar 518
                continue;              
1 jermar 519
 
413 jermar 520
restart:        ipl = interrupts_disable();
115 jermar 521
            r = &cpu->rq[j];
1 jermar 522
            spinlock_lock(&r->lock);
523
            if (r->n == 0) {
524
                spinlock_unlock(&r->lock);
413 jermar 525
                interrupts_restore(ipl);
1 jermar 526
                continue;
527
            }
528
 
529
            t = NULL;
530
            l = r->rq_head.prev;    /* search rq from the back */
531
            while (l != &r->rq_head) {
532
                t = list_get_instance(l, thread_t, rq_link);
533
                /*
125 jermar 534
                 * We don't want to steal CPU-wired threads neither threads already stolen.
1 jermar 535
                 * The latter prevents threads from migrating between CPU's without ever being run.
125 jermar 536
                 * We don't want to steal threads whose FPU context is still in CPU.
73 vana 537
                 */
1 jermar 538
                spinlock_lock(&t->lock);
73 vana 539
                if ( (!(t->flags & (X_WIRED | X_STOLEN))) && (!(t->fpu_context_engaged)) ) {
115 jermar 540
 
1 jermar 541
                    /*
542
                     * Remove t from r.
543
                     */
544
 
545
                    spinlock_unlock(&t->lock);
546
 
547
                    /*
548
                     * Here we have to avoid deadlock with relink_rq(),
549
                     * because it locks cpu and r in a different order than we do.
550
                     */
551
                    if (!spinlock_trylock(&cpu->lock)) {
552
                        /* Release all locks and try again. */
553
                        spinlock_unlock(&r->lock);
413 jermar 554
                        interrupts_restore(ipl);
1 jermar 555
                        goto restart;
556
                    }
557
                    cpu->nrdy--;
558
                    spinlock_unlock(&cpu->lock);
559
 
258 palkovsky 560
                    atomic_dec((int *)&nrdy);
1 jermar 561
 
125 jermar 562
                    r->n--;
1 jermar 563
                    list_remove(&t->rq_link);
564
 
565
                    break;
566
                }
567
                spinlock_unlock(&t->lock);
568
                l = l->prev;
569
                t = NULL;
570
            }
571
            spinlock_unlock(&r->lock);
572
 
573
            if (t) {
574
                /*
575
                 * Ready t on local CPU
576
                 */
577
                spinlock_lock(&t->lock);
578
                #ifdef KCPULB_VERBOSE
15 jermar 579
                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 580
                #endif
581
                t->flags |= X_STOLEN;
582
                spinlock_unlock(&t->lock);
583
 
584
                thread_ready(t);
585
 
413 jermar 586
                interrupts_restore(ipl);
1 jermar 587
 
588
                if (--count == 0)
589
                    goto satisfied;
590
 
591
                /*
125 jermar 592
                 * We are not satisfied yet, focus on another CPU next time.
1 jermar 593
                 */
594
                k++;
595
 
596
                continue;
597
            }
413 jermar 598
            interrupts_restore(ipl);
1 jermar 599
        }
600
    }
601
 
15 jermar 602
    if (CPU->nrdy) {
1 jermar 603
        /*
604
         * Be a little bit light-weight and let migrated threads run.
605
         */
606
        scheduler();
607
    }
608
    else {
609
        /*
610
         * We failed to migrate a single thread.
611
         * Something more sophisticated should be done.
612
         */
613
        scheduler();
614
    }
615
 
616
    goto not_satisfied;
125 jermar 617
 
1 jermar 618
satisfied:
619
    /*
620
     * Tell find_best_thread() to wake us up later again.
621
     */
15 jermar 622
    CPU->kcpulbstarted = 0;
1 jermar 623
    goto loop;
624
}
625
 
626
#endif /* __SMP__ */