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1
/*
1
/*
2
 * Copyright (C) 2001-2004 Jakub Jermar
2
 * Copyright (C) 2001-2004 Jakub Jermar
3
 * All rights reserved.
3
 * All rights reserved.
4
 *
4
 *
5
 * Redistribution and use in source and binary forms, with or without
5
 * Redistribution and use in source and binary forms, with or without
6
 * modification, are permitted provided that the following conditions
6
 * modification, are permitted provided that the following conditions
7
 * are met:
7
 * are met:
8
 *
8
 *
9
 * - Redistributions of source code must retain the above copyright
9
 * - Redistributions of source code must retain the above copyright
10
 *   notice, this list of conditions and the following disclaimer.
10
 *   notice, this list of conditions and the following disclaimer.
11
 * - Redistributions in binary form must reproduce the above copyright
11
 * - Redistributions in binary form must reproduce the above copyright
12
 *   notice, this list of conditions and the following disclaimer in the
12
 *   notice, this list of conditions and the following disclaimer in the
13
 *   documentation and/or other materials provided with the distribution.
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
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.
15
 *   derived from this software without specific prior written permission.
16
 *
16
 *
17
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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
18
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
19
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
19
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
20
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
20
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
21
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
21
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
22
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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
23
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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
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.
26
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27
 */
27
 */
28
 
28
 
29
#include <proc/scheduler.h>
29
#include <proc/scheduler.h>
30
#include <proc/thread.h>
30
#include <proc/thread.h>
31
#include <proc/task.h>
31
#include <proc/task.h>
32
#include <mm/heap.h>
32
#include <mm/heap.h>
33
#include <mm/frame.h>
33
#include <mm/frame.h>
34
#include <mm/page.h>
34
#include <mm/page.h>
35
#include <mm/vm.h>
35
#include <mm/vm.h>
36
#include <arch/asm.h>
36
#include <arch/asm.h>
37
#include <arch/faddr.h>
37
#include <arch/faddr.h>
38
#include <arch/atomic.h>
38
#include <arch/atomic.h>
39
#include <synch/spinlock.h>
39
#include <synch/spinlock.h>
40
#include <config.h>
40
#include <config.h>
41
#include <context.h>
41
#include <context.h>
42
#include <func.h>
42
#include <func.h>
43
#include <arch.h>
43
#include <arch.h>
44
#include <list.h>
44
#include <list.h>
45
#include <panic.h>
45
#include <panic.h>
46
#include <typedefs.h>
46
#include <typedefs.h>
47
#include <cpu.h>
47
#include <cpu.h>
48
#include <print.h>
48
#include <print.h>
49
#include <debug.h>
49
#include <debug.h>
50
 
50
 
51
volatile count_t nrdy;
51
volatile count_t nrdy;
52
 
52
 
53
 
53
 
54
/** Take actions before new thread runs
54
/** Take actions before new thread runs
55
 *
55
 *
56
 * Perform actions that need to be
56
 * Perform actions that need to be
57
 * taken before the newly selected
57
 * taken before the newly selected
58
 * tread is passed control.
58
 * tread is passed control.
59
 *
59
 *
60
 */
60
 */
61
void before_thread_runs(void)
61
void before_thread_runs(void)
62
{
62
{
63
    before_thread_runs_arch();
63
    before_thread_runs_arch();
64
#ifdef FPU_LAZY
64
#ifdef FPU_LAZY
65
    if(THREAD==CPU->fpu_owner)
65
    if(THREAD==CPU->fpu_owner)
66
        fpu_enable();
66
        fpu_enable();
67
    else
67
    else
68
        fpu_disable();
68
        fpu_disable();
69
#else
69
#else
70
    fpu_enable();
70
    fpu_enable();
71
    if (THREAD->fpu_context_exists)
71
    if (THREAD->fpu_context_exists)
72
        fpu_context_restore(&(THREAD->saved_fpu_context));
72
        fpu_context_restore(&(THREAD->saved_fpu_context));
73
    else {
73
    else {
74
        fpu_init();
74
        fpu_init();
75
        THREAD->fpu_context_exists=1;
75
        THREAD->fpu_context_exists=1;
76
    }
76
    }
77
#endif
77
#endif
78
}
78
}
79
 
79
 
80
#ifdef FPU_LAZY
80
#ifdef FPU_LAZY
81
void scheduler_fpu_lazy_request(void)
81
void scheduler_fpu_lazy_request(void)
82
{
82
{
83
    fpu_enable();
83
    fpu_enable();
84
    if (CPU->fpu_owner != NULL) {  
84
    if (CPU->fpu_owner != NULL) {  
85
        fpu_context_save(&CPU->fpu_owner->saved_fpu_context);
85
        fpu_context_save(&CPU->fpu_owner->saved_fpu_context);
86
        /* don't prevent migration */
86
        /* don't prevent migration */
87
        CPU->fpu_owner->fpu_context_engaged=0;
87
        CPU->fpu_owner->fpu_context_engaged=0;
88
    }
88
    }
89
    if (THREAD->fpu_context_exists)
89
    if (THREAD->fpu_context_exists)
90
        fpu_context_restore(&THREAD->saved_fpu_context);
90
        fpu_context_restore(&THREAD->saved_fpu_context);
91
    else {
91
    else {
92
        fpu_init();
92
        fpu_init();
93
        THREAD->fpu_context_exists=1;
93
        THREAD->fpu_context_exists=1;
94
    }
94
    }
95
    CPU->fpu_owner=THREAD;
95
    CPU->fpu_owner=THREAD;
96
    THREAD->fpu_context_engaged = 1;
96
    THREAD->fpu_context_engaged = 1;
97
}
97
}
98
#endif
98
#endif
99
 
99
 
100
/** Initialize scheduler
100
/** Initialize scheduler
101
 *
101
 *
102
 * Initialize kernel scheduler.
102
 * Initialize kernel scheduler.
103
 *
103
 *
104
 */
104
 */
105
void scheduler_init(void)
105
void scheduler_init(void)
106
{
106
{
107
}
107
}
108
 
108
 
109
 
109
 
110
/** Get thread to be scheduled
110
/** Get thread to be scheduled
111
 *
111
 *
112
 * Get the optimal thread to be scheduled
112
 * Get the optimal thread to be scheduled
113
 * according to thread accounting and scheduler
113
 * according to thread accounting and scheduler
114
 * policy.
114
 * policy.
115
 *
115
 *
116
 * @return Thread to be scheduled.
116
 * @return Thread to be scheduled.
117
 *
117
 *
118
 */
118
 */
119
struct thread *find_best_thread(void)
119
struct thread *find_best_thread(void)
120
{
120
{
121
    thread_t *t;
121
    thread_t *t;
122
    runq_t *r;
122
    runq_t *r;
123
    int i, n;
123
    int i, n;
124
 
124
 
125
    ASSERT(CPU != NULL);
125
    ASSERT(CPU != NULL);
126
 
126
 
127
loop:
127
loop:
128
    interrupts_disable();
128
    interrupts_disable();
129
 
129
 
130
    spinlock_lock(&CPU->lock);
130
    spinlock_lock(&CPU->lock);
131
    n = CPU->nrdy;
131
    n = CPU->nrdy;
132
    spinlock_unlock(&CPU->lock);
132
    spinlock_unlock(&CPU->lock);
133
 
133
 
134
    interrupts_enable();
134
    interrupts_enable();
135
   
135
   
136
    if (n == 0) {
136
    if (n == 0) {
137
        #ifdef __SMP__
137
        #ifdef __SMP__
138
        /*
138
        /*
139
         * If the load balancing thread is not running, wake it up and
139
         * If the load balancing thread is not running, wake it up and
140
         * set CPU-private flag that the kcpulb has been started.
140
         * set CPU-private flag that the kcpulb has been started.
141
         */
141
         */
142
        if (test_and_set(&CPU->kcpulbstarted) == 0) {
142
        if (test_and_set(&CPU->kcpulbstarted) == 0) {
143
            waitq_wakeup(&CPU->kcpulb_wq, 0);
143
            waitq_wakeup(&CPU->kcpulb_wq, 0);
144
            goto loop;
144
            goto loop;
145
        }
145
        }
146
        #endif /* __SMP__ */
146
        #endif /* __SMP__ */
147
       
147
       
148
        /*
148
        /*
149
         * For there was nothing to run, the CPU goes to sleep
149
         * For there was nothing to run, the CPU goes to sleep
150
         * until a hardware interrupt or an IPI comes.
150
         * until a hardware interrupt or an IPI comes.
151
         * This improves energy saving and hyperthreading.
151
         * This improves energy saving and hyperthreading.
152
         * On the other hand, several hardware interrupts can be ignored.
152
         * On the other hand, several hardware interrupts can be ignored.
153
         */
153
         */
154
         cpu_sleep();
154
         cpu_sleep();
155
         goto loop;
155
         goto loop;
156
    }
156
    }
157
 
157
 
158
    interrupts_disable();
158
    interrupts_disable();
159
   
159
   
160
    i = 0;
160
    i = 0;
161
retry:
161
retry:
162
    for (; i<RQ_COUNT; i++) {
162
    for (; i<RQ_COUNT; i++) {
163
        r = &CPU->rq[i];
163
        r = &CPU->rq[i];
164
        spinlock_lock(&r->lock);
164
        spinlock_lock(&r->lock);
165
        if (r->n == 0) {
165
        if (r->n == 0) {
166
            /*
166
            /*
167
             * If this queue is empty, try a lower-priority queue.
167
             * If this queue is empty, try a lower-priority queue.
168
             */
168
             */
169
            spinlock_unlock(&r->lock);
169
            spinlock_unlock(&r->lock);
170
            continue;
170
            continue;
171
        }
171
        }
172
 
172
 
173
        /* avoid deadlock with relink_rq() */
173
        /* avoid deadlock with relink_rq() */
174
        if (!spinlock_trylock(&CPU->lock)) {
174
        if (!spinlock_trylock(&CPU->lock)) {
175
            /*
175
            /*
176
             * Unlock r and try again.
176
             * Unlock r and try again.
177
             */
177
             */
178
            spinlock_unlock(&r->lock);
178
            spinlock_unlock(&r->lock);
179
            goto retry;
179
            goto retry;
180
        }
180
        }
181
        CPU->nrdy--;
181
        CPU->nrdy--;
182
        spinlock_unlock(&CPU->lock);
182
        spinlock_unlock(&CPU->lock);
183
 
183
 
184
        atomic_dec((int *) &nrdy);
184
        atomic_dec((int *) &nrdy);
185
        r->n--;
185
        r->n--;
186
 
186
 
187
        /*
187
        /*
188
         * Take the first thread from the queue.
188
         * Take the first thread from the queue.
189
         */
189
         */
190
        t = list_get_instance(r->rq_head.next, thread_t, rq_link);
190
        t = list_get_instance(r->rq_head.next, thread_t, rq_link);
191
        list_remove(&t->rq_link);
191
        list_remove(&t->rq_link);
192
 
192
 
193
        spinlock_unlock(&r->lock);
193
        spinlock_unlock(&r->lock);
194
 
194
 
195
        spinlock_lock(&t->lock);
195
        spinlock_lock(&t->lock);
196
        t->cpu = CPU;
196
        t->cpu = CPU;
197
 
197
 
198
        t->ticks = us2ticks((i+1)*10000);
198
        t->ticks = us2ticks((i+1)*10000);
199
        t->priority = i;    /* eventually correct rq index */
199
        t->priority = i;    /* eventually correct rq index */
200
 
200
 
201
        /*
201
        /*
202
         * Clear the X_STOLEN flag so that t can be migrated when load balancing needs emerge.
202
         * Clear the X_STOLEN flag so that t can be migrated when load balancing needs emerge.
203
         */
203
         */
204
        t->flags &= ~X_STOLEN;
204
        t->flags &= ~X_STOLEN;
205
        spinlock_unlock(&t->lock);
205
        spinlock_unlock(&t->lock);
206
 
206
 
207
        return t;
207
        return t;
208
    }
208
    }
209
    goto loop;
209
    goto loop;
210
 
210
 
211
}
211
}
212
 
212
 
213
 
213
 
214
/** Prevent rq starvation
214
/** Prevent rq starvation
215
 *
215
 *
216
 * Prevent low priority threads from starving in rq's.
216
 * Prevent low priority threads from starving in rq's.
217
 *
217
 *
218
 * When the function decides to relink rq's, it reconnects
218
 * When the function decides to relink rq's, it reconnects
219
 * respective pointers so that in result threads with 'pri'
219
 * respective pointers so that in result threads with 'pri'
220
 * greater or equal 'start' are moved to a higher-priority queue.
220
 * greater or equal 'start' are moved to a higher-priority queue.
221
 *
221
 *
222
 * @param start Threshold priority.
222
 * @param start Threshold priority.
223
 *
223
 *
224
 */
224
 */
225
void relink_rq(int start)
225
void relink_rq(int start)
226
{
226
{
227
    link_t head;
227
    link_t head;
228
    runq_t *r;
228
    runq_t *r;
229
    int i, n;
229
    int i, n;
230
 
230
 
231
    list_initialize(&head);
231
    list_initialize(&head);
232
    spinlock_lock(&CPU->lock);
232
    spinlock_lock(&CPU->lock);
233
    if (CPU->needs_relink > NEEDS_RELINK_MAX) {
233
    if (CPU->needs_relink > NEEDS_RELINK_MAX) {
234
        for (i = start; i<RQ_COUNT-1; i++) {
234
        for (i = start; i<RQ_COUNT-1; i++) {
235
            /* remember and empty rq[i + 1] */
235
            /* remember and empty rq[i + 1] */
236
            r = &CPU->rq[i + 1];
236
            r = &CPU->rq[i + 1];
237
            spinlock_lock(&r->lock);
237
            spinlock_lock(&r->lock);
238
            list_concat(&head, &r->rq_head);
238
            list_concat(&head, &r->rq_head);
239
            n = r->n;
239
            n = r->n;
240
            r->n = 0;
240
            r->n = 0;
241
            spinlock_unlock(&r->lock);
241
            spinlock_unlock(&r->lock);
242
       
242
       
243
            /* append rq[i + 1] to rq[i] */
243
            /* append rq[i + 1] to rq[i] */
244
            r = &CPU->rq[i];
244
            r = &CPU->rq[i];
245
            spinlock_lock(&r->lock);
245
            spinlock_lock(&r->lock);
246
            list_concat(&r->rq_head, &head);
246
            list_concat(&r->rq_head, &head);
247
            r->n += n;
247
            r->n += n;
248
            spinlock_unlock(&r->lock);
248
            spinlock_unlock(&r->lock);
249
        }
249
        }
250
        CPU->needs_relink = 0;
250
        CPU->needs_relink = 0;
251
    }
251
    }
252
    spinlock_unlock(&CPU->lock);               
252
    spinlock_unlock(&CPU->lock);               
253
 
253
 
254
}
254
}
255
 
255
 
256
 
256
 
257
/** The scheduler
257
/** The scheduler
258
 *
258
 *
259
 * The thread scheduling procedure.
259
 * The thread scheduling procedure.
260
 *
260
 *
261
 */
261
 */
262
void scheduler(void)
262
void scheduler(void)
263
{
263
{
264
    volatile ipl_t ipl;
264
    volatile ipl_t ipl;
265
 
265
 
266
    ASSERT(CPU != NULL);
266
    ASSERT(CPU != NULL);
267
 
267
 
268
    ipl = interrupts_disable();
268
    ipl = interrupts_disable();
269
 
269
 
270
    if (haltstate)
270
    if (haltstate)
271
        halt();
271
        halt();
272
 
272
 
273
    if (THREAD) {
273
    if (THREAD) {
274
        spinlock_lock(&THREAD->lock);
274
        spinlock_lock(&THREAD->lock);
275
#ifndef FPU_LAZY
275
#ifndef FPU_LAZY
276
        fpu_context_save(&(THREAD->saved_fpu_context));
276
        fpu_context_save(&(THREAD->saved_fpu_context));
277
#endif
277
#endif
278
        if (!context_save(&THREAD->saved_context)) {
278
        if (!context_save(&THREAD->saved_context)) {
279
            /*
279
            /*
280
             * This is the place where threads leave scheduler();
280
             * This is the place where threads leave scheduler();
281
             */
281
             */
282
            before_thread_runs();
282
            before_thread_runs();
283
            spinlock_unlock(&THREAD->lock);
283
            spinlock_unlock(&THREAD->lock);
284
            interrupts_restore(THREAD->saved_context.ipl);
284
            interrupts_restore(THREAD->saved_context.ipl);
285
            return;
285
            return;
286
        }
286
        }
287
 
287
 
288
        /*
288
        /*
289
         * Interrupt priority level of preempted thread is recorded here
289
         * Interrupt priority level of preempted thread is recorded here
290
         * to facilitate scheduler() invocations from interrupts_disable()'d
290
         * to facilitate scheduler() invocations from interrupts_disable()'d
291
         * code (e.g. waitq_sleep_timeout()).
291
         * code (e.g. waitq_sleep_timeout()).
292
         */
292
         */
293
        THREAD->saved_context.ipl = ipl;
293
        THREAD->saved_context.ipl = ipl;
294
    }
294
    }
295
 
295
 
296
    /*
296
    /*
297
     * Through the 'THE' structure, we keep track of THREAD, TASK, CPU
297
     * Through the 'THE' structure, we keep track of THREAD, TASK, CPU
298
     * and preemption counter. At this point THE could be coming either
298
     * and preemption counter. At this point THE could be coming either
299
     * from THREAD's or CPU's stack.
299
     * from THREAD's or CPU's stack.
300
     */
300
     */
301
    the_copy(THE, (the_t *) CPU->stack);
301
    the_copy(THE, (the_t *) CPU->stack);
302
 
302
 
303
    /*
303
    /*
304
     * We may not keep the old stack.
304
     * We may not keep the old stack.
305
     * Reason: If we kept the old stack and got blocked, for instance, in
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
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
307
     * CPU and overwrite the part of its own stack that was also used by
308
     * the scheduler on this CPU.
308
     * the scheduler on this CPU.
309
     *
309
     *
310
     * Moreover, we have to bypass the compiler-generated POP sequence
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.
311
     * which is fooled by SP being set to the very top of the stack.
312
     * Therefore the scheduler() function continues in
312
     * Therefore the scheduler() function continues in
313
     * scheduler_separated_stack().
313
     * scheduler_separated_stack().
314
     */
314
     */
315
    context_save(&CPU->saved_context);
315
    context_save(&CPU->saved_context);
316
    context_set(&CPU->saved_context, FADDR(scheduler_separated_stack), CPU->stack, CPU_STACK_SIZE);
316
    context_set(&CPU->saved_context, FADDR(scheduler_separated_stack), (__address) CPU->stack, CPU_STACK_SIZE);
317
    context_restore(&CPU->saved_context);
317
    context_restore(&CPU->saved_context);
318
    /* not reached */
318
    /* not reached */
319
}
319
}
320
 
320
 
321
 
321
 
322
/** Scheduler stack switch wrapper
322
/** Scheduler stack switch wrapper
323
 *
323
 *
324
 * Second part of the scheduler() function
324
 * Second part of the scheduler() function
325
 * using new stack. Handling the actual context
325
 * using new stack. Handling the actual context
326
 * switch to a new thread.
326
 * switch to a new thread.
327
 *
327
 *
328
 */
328
 */
329
void scheduler_separated_stack(void)
329
void scheduler_separated_stack(void)
330
{
330
{
331
    int priority;
331
    int priority;
332
 
332
 
333
    ASSERT(CPU != NULL);
333
    ASSERT(CPU != NULL);
334
 
334
 
335
    if (THREAD) {
335
    if (THREAD) {
336
        switch (THREAD->state) {
336
        switch (THREAD->state) {
337
            case Running:
337
            case Running:
338
            THREAD->state = Ready;
338
            THREAD->state = Ready;
339
            spinlock_unlock(&THREAD->lock);
339
            spinlock_unlock(&THREAD->lock);
340
            thread_ready(THREAD);
340
            thread_ready(THREAD);
341
            break;
341
            break;
342
 
342
 
343
            case Exiting:
343
            case Exiting:
344
            frame_free((__address) THREAD->kstack);
344
            frame_free((__address) THREAD->kstack);
345
            if (THREAD->ustack) {
345
            if (THREAD->ustack) {
346
                frame_free((__address) THREAD->ustack);
346
                frame_free((__address) THREAD->ustack);
347
            }
347
            }
348
 
348
 
349
            /*
349
            /*
350
             * Detach from the containing task.
350
             * Detach from the containing task.
351
             */
351
             */
352
            spinlock_lock(&TASK->lock);
352
            spinlock_lock(&TASK->lock);
353
            list_remove(&THREAD->th_link);
353
            list_remove(&THREAD->th_link);
354
            spinlock_unlock(&TASK->lock);
354
            spinlock_unlock(&TASK->lock);
355
 
355
 
356
            spinlock_unlock(&THREAD->lock);
356
            spinlock_unlock(&THREAD->lock);
357
   
357
   
358
            spinlock_lock(&threads_lock);
358
            spinlock_lock(&threads_lock);
359
            list_remove(&THREAD->threads_link);
359
            list_remove(&THREAD->threads_link);
360
            spinlock_unlock(&threads_lock);
360
            spinlock_unlock(&threads_lock);
361
 
361
 
362
            spinlock_lock(&CPU->lock);
362
            spinlock_lock(&CPU->lock);
363
            if(CPU->fpu_owner==THREAD) CPU->fpu_owner=NULL;
363
            if(CPU->fpu_owner==THREAD) CPU->fpu_owner=NULL;
364
            spinlock_unlock(&CPU->lock);
364
            spinlock_unlock(&CPU->lock);
365
 
365
 
366
            free(THREAD);
366
            free(THREAD);
367
 
367
 
368
            break;
368
            break;
369
   
369
   
370
            case Sleeping:
370
            case Sleeping:
371
            /*
371
            /*
372
             * Prefer the thread after it's woken up.
372
             * Prefer the thread after it's woken up.
373
             */
373
             */
374
            THREAD->priority = -1;
374
            THREAD->priority = -1;
375
 
375
 
376
            /*
376
            /*
377
             * We need to release wq->lock which we locked in waitq_sleep().
377
             * We need to release wq->lock which we locked in waitq_sleep().
378
             * Address of wq->lock is kept in THREAD->sleep_queue.
378
             * Address of wq->lock is kept in THREAD->sleep_queue.
379
             */
379
             */
380
            spinlock_unlock(&THREAD->sleep_queue->lock);
380
            spinlock_unlock(&THREAD->sleep_queue->lock);
381
 
381
 
382
            /*
382
            /*
383
             * Check for possible requests for out-of-context invocation.
383
             * Check for possible requests for out-of-context invocation.
384
             */
384
             */
385
            if (THREAD->call_me) {
385
            if (THREAD->call_me) {
386
                THREAD->call_me(THREAD->call_me_with);
386
                THREAD->call_me(THREAD->call_me_with);
387
                THREAD->call_me = NULL;
387
                THREAD->call_me = NULL;
388
                THREAD->call_me_with = NULL;
388
                THREAD->call_me_with = NULL;
389
            }
389
            }
390
 
390
 
391
            spinlock_unlock(&THREAD->lock);
391
            spinlock_unlock(&THREAD->lock);
392
 
392
 
393
            break;
393
            break;
394
 
394
 
395
            default:
395
            default:
396
            /*
396
            /*
397
             * Entering state is unexpected.
397
             * Entering state is unexpected.
398
             */
398
             */
399
            panic("tid%d: unexpected state %s\n", THREAD->tid, thread_states[THREAD->state]);
399
            panic("tid%d: unexpected state %s\n", THREAD->tid, thread_states[THREAD->state]);
400
            break;
400
            break;
401
        }
401
        }
402
        THREAD = NULL;
402
        THREAD = NULL;
403
    }
403
    }
404
 
404
 
405
 
405
 
406
    THREAD = find_best_thread();
406
    THREAD = find_best_thread();
407
   
407
   
408
    spinlock_lock(&THREAD->lock);
408
    spinlock_lock(&THREAD->lock);
409
    priority = THREAD->priority;
409
    priority = THREAD->priority;
410
    spinlock_unlock(&THREAD->lock);
410
    spinlock_unlock(&THREAD->lock);
411
 
411
 
412
    relink_rq(priority);       
412
    relink_rq(priority);       
413
 
413
 
414
    spinlock_lock(&THREAD->lock);  
414
    spinlock_lock(&THREAD->lock);  
415
 
415
 
416
    /*
416
    /*
417
     * If both the old and the new task are the same, lots of work is avoided.
417
     * If both the old and the new task are the same, lots of work is avoided.
418
     */
418
     */
419
    if (TASK != THREAD->task) {
419
    if (TASK != THREAD->task) {
420
        vm_t *m1 = NULL;
420
        vm_t *m1 = NULL;
421
        vm_t *m2;
421
        vm_t *m2;
422
 
422
 
423
        if (TASK) {
423
        if (TASK) {
424
            spinlock_lock(&TASK->lock);
424
            spinlock_lock(&TASK->lock);
425
            m1 = TASK->vm;
425
            m1 = TASK->vm;
426
            spinlock_unlock(&TASK->lock);
426
            spinlock_unlock(&TASK->lock);
427
        }
427
        }
428
 
428
 
429
        spinlock_lock(&THREAD->task->lock);
429
        spinlock_lock(&THREAD->task->lock);
430
        m2 = THREAD->task->vm;
430
        m2 = THREAD->task->vm;
431
        spinlock_unlock(&THREAD->task->lock);
431
        spinlock_unlock(&THREAD->task->lock);
432
       
432
       
433
        /*
433
        /*
434
         * Note that it is possible for two tasks to share one vm mapping.
434
         * Note that it is possible for two tasks to share one vm mapping.
435
         */
435
         */
436
        if (m1 != m2) {
436
        if (m1 != m2) {
437
            /*
437
            /*
438
             * Both tasks and vm mappings are different.
438
             * Both tasks and vm mappings are different.
439
             * Replace the old one with the new one.
439
             * Replace the old one with the new one.
440
             */
440
             */
441
            vm_install(m2);
441
            vm_install(m2);
442
        }
442
        }
443
        TASK = THREAD->task;   
443
        TASK = THREAD->task;   
444
    }
444
    }
445
 
445
 
446
    THREAD->state = Running;
446
    THREAD->state = Running;
447
 
447
 
448
    #ifdef SCHEDULER_VERBOSE
448
    #ifdef SCHEDULER_VERBOSE
449
    printf("cpu%d: tid %d (priority=%d,ticks=%d,nrdy=%d)\n", CPU->id, THREAD->tid, THREAD->priority, THREAD->ticks, CPU->nrdy);
449
    printf("cpu%d: tid %d (priority=%d,ticks=%d,nrdy=%d)\n", CPU->id, THREAD->tid, THREAD->priority, THREAD->ticks, CPU->nrdy);
450
    #endif  
450
    #endif  
451
 
451
 
452
    /*
452
    /*
453
     * Copy the knowledge of CPU, TASK, THREAD and preemption counter to thread's stack.
453
     * Copy the knowledge of CPU, TASK, THREAD and preemption counter to thread's stack.
454
     */
454
     */
455
    the_copy(THE, (the_t *) THREAD->kstack);
455
    the_copy(THE, (the_t *) THREAD->kstack);
456
   
456
   
457
    context_restore(&THREAD->saved_context);
457
    context_restore(&THREAD->saved_context);
458
    /* not reached */
458
    /* not reached */
459
}
459
}
460
 
460
 
461
 
461
 
462
#ifdef __SMP__
462
#ifdef __SMP__
463
/** Load balancing thread
463
/** Load balancing thread
464
 *
464
 *
465
 * SMP load balancing thread, supervising thread supplies
465
 * SMP load balancing thread, supervising thread supplies
466
 * for the CPU it's wired to.
466
 * for the CPU it's wired to.
467
 *
467
 *
468
 * @param arg Generic thread argument (unused).
468
 * @param arg Generic thread argument (unused).
469
 *
469
 *
470
 */
470
 */
471
void kcpulb(void *arg)
471
void kcpulb(void *arg)
472
{
472
{
473
    thread_t *t;
473
    thread_t *t;
474
    int count, i, j, k = 0;
474
    int count, i, j, k = 0;
475
    ipl_t ipl;
475
    ipl_t ipl;
476
 
476
 
477
loop:
477
loop:
478
    /*
478
    /*
479
     * Sleep until there's some work to do.
479
     * Sleep until there's some work to do.
480
     */
480
     */
481
    waitq_sleep(&CPU->kcpulb_wq);
481
    waitq_sleep(&CPU->kcpulb_wq);
482
 
482
 
483
not_satisfied:
483
not_satisfied:
484
    /*
484
    /*
485
     * Calculate the number of threads that will be migrated/stolen from
485
     * Calculate the number of threads that will be migrated/stolen from
486
     * other CPU's. Note that situation can have changed between two
486
     * other CPU's. Note that situation can have changed between two
487
     * passes. Each time get the most up to date counts.
487
     * passes. Each time get the most up to date counts.
488
     */
488
     */
489
    ipl = interrupts_disable();
489
    ipl = interrupts_disable();
490
    spinlock_lock(&CPU->lock);
490
    spinlock_lock(&CPU->lock);
491
    count = nrdy / config.cpu_active;
491
    count = nrdy / config.cpu_active;
492
    count -= CPU->nrdy;
492
    count -= CPU->nrdy;
493
    spinlock_unlock(&CPU->lock);
493
    spinlock_unlock(&CPU->lock);
494
    interrupts_restore(ipl);
494
    interrupts_restore(ipl);
495
 
495
 
496
    if (count <= 0)
496
    if (count <= 0)
497
        goto satisfied;
497
        goto satisfied;
498
 
498
 
499
    /*
499
    /*
500
     * Searching least priority queues on all CPU's first and most priority queues on all CPU's last.
500
     * Searching least priority queues on all CPU's first and most priority queues on all CPU's last.
501
     */
501
     */
502
    for (j=RQ_COUNT-1; j >= 0; j--) {
502
    for (j=RQ_COUNT-1; j >= 0; j--) {
503
        for (i=0; i < config.cpu_active; i++) {
503
        for (i=0; i < config.cpu_active; i++) {
504
            link_t *l;
504
            link_t *l;
505
            runq_t *r;
505
            runq_t *r;
506
            cpu_t *cpu;
506
            cpu_t *cpu;
507
 
507
 
508
            cpu = &cpus[(i + k) % config.cpu_active];
508
            cpu = &cpus[(i + k) % config.cpu_active];
509
 
509
 
510
            /*
510
            /*
511
             * Not interested in ourselves.
511
             * Not interested in ourselves.
512
             * Doesn't require interrupt disabling for kcpulb is X_WIRED.
512
             * Doesn't require interrupt disabling for kcpulb is X_WIRED.
513
             */
513
             */
514
            if (CPU == cpu)
514
            if (CPU == cpu)
515
                continue;              
515
                continue;              
516
 
516
 
517
restart:        ipl = interrupts_disable();
517
restart:        ipl = interrupts_disable();
518
            r = &cpu->rq[j];
518
            r = &cpu->rq[j];
519
            spinlock_lock(&r->lock);
519
            spinlock_lock(&r->lock);
520
            if (r->n == 0) {
520
            if (r->n == 0) {
521
                spinlock_unlock(&r->lock);
521
                spinlock_unlock(&r->lock);
522
                interrupts_restore(ipl);
522
                interrupts_restore(ipl);
523
                continue;
523
                continue;
524
            }
524
            }
525
       
525
       
526
            t = NULL;
526
            t = NULL;
527
            l = r->rq_head.prev;    /* search rq from the back */
527
            l = r->rq_head.prev;    /* search rq from the back */
528
            while (l != &r->rq_head) {
528
            while (l != &r->rq_head) {
529
                t = list_get_instance(l, thread_t, rq_link);
529
                t = list_get_instance(l, thread_t, rq_link);
530
                /*
530
                /*
531
                 * We don't want to steal CPU-wired threads neither threads already stolen.
531
                 * We don't want to steal CPU-wired threads neither threads already stolen.
532
                 * The latter prevents threads from migrating between CPU's without ever being run.
532
                 * The latter prevents threads from migrating between CPU's without ever being run.
533
                 * We don't want to steal threads whose FPU context is still in CPU.
533
                 * We don't want to steal threads whose FPU context is still in CPU.
534
                 */
534
                 */
535
                spinlock_lock(&t->lock);
535
                spinlock_lock(&t->lock);
536
                if ( (!(t->flags & (X_WIRED | X_STOLEN))) && (!(t->fpu_context_engaged)) ) {
536
                if ( (!(t->flags & (X_WIRED | X_STOLEN))) && (!(t->fpu_context_engaged)) ) {
537
               
537
               
538
                    /*
538
                    /*
539
                     * Remove t from r.
539
                     * Remove t from r.
540
                     */
540
                     */
541
 
541
 
542
                    spinlock_unlock(&t->lock);
542
                    spinlock_unlock(&t->lock);
543
                   
543
                   
544
                    /*
544
                    /*
545
                     * Here we have to avoid deadlock with relink_rq(),
545
                     * Here we have to avoid deadlock with relink_rq(),
546
                     * because it locks cpu and r in a different order than we do.
546
                     * because it locks cpu and r in a different order than we do.
547
                     */
547
                     */
548
                    if (!spinlock_trylock(&cpu->lock)) {
548
                    if (!spinlock_trylock(&cpu->lock)) {
549
                        /* Release all locks and try again. */
549
                        /* Release all locks and try again. */
550
                        spinlock_unlock(&r->lock);
550
                        spinlock_unlock(&r->lock);
551
                        interrupts_restore(ipl);
551
                        interrupts_restore(ipl);
552
                        goto restart;
552
                        goto restart;
553
                    }
553
                    }
554
                    cpu->nrdy--;
554
                    cpu->nrdy--;
555
                    spinlock_unlock(&cpu->lock);
555
                    spinlock_unlock(&cpu->lock);
556
 
556
 
557
                    atomic_dec((int *)&nrdy);
557
                    atomic_dec((int *)&nrdy);
558
 
558
 
559
                    r->n--;
559
                    r->n--;
560
                    list_remove(&t->rq_link);
560
                    list_remove(&t->rq_link);
561
 
561
 
562
                    break;
562
                    break;
563
                }
563
                }
564
                spinlock_unlock(&t->lock);
564
                spinlock_unlock(&t->lock);
565
                l = l->prev;
565
                l = l->prev;
566
                t = NULL;
566
                t = NULL;
567
            }
567
            }
568
            spinlock_unlock(&r->lock);
568
            spinlock_unlock(&r->lock);
569
 
569
 
570
            if (t) {
570
            if (t) {
571
                /*
571
                /*
572
                 * Ready t on local CPU
572
                 * Ready t on local CPU
573
                 */
573
                 */
574
                spinlock_lock(&t->lock);
574
                spinlock_lock(&t->lock);
575
                #ifdef KCPULB_VERBOSE
575
                #ifdef KCPULB_VERBOSE
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);
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);
577
                #endif
577
                #endif
578
                t->flags |= X_STOLEN;
578
                t->flags |= X_STOLEN;
579
                spinlock_unlock(&t->lock);
579
                spinlock_unlock(&t->lock);
580
   
580
   
581
                thread_ready(t);
581
                thread_ready(t);
582
 
582
 
583
                interrupts_restore(ipl);
583
                interrupts_restore(ipl);
584
   
584
   
585
                if (--count == 0)
585
                if (--count == 0)
586
                    goto satisfied;
586
                    goto satisfied;
587
                   
587
                   
588
                /*
588
                /*
589
                 * We are not satisfied yet, focus on another CPU next time.
589
                 * We are not satisfied yet, focus on another CPU next time.
590
                 */
590
                 */
591
                k++;
591
                k++;
592
               
592
               
593
                continue;
593
                continue;
594
            }
594
            }
595
            interrupts_restore(ipl);
595
            interrupts_restore(ipl);
596
        }
596
        }
597
    }
597
    }
598
 
598
 
599
    if (CPU->nrdy) {
599
    if (CPU->nrdy) {
600
        /*
600
        /*
601
         * Be a little bit light-weight and let migrated threads run.
601
         * Be a little bit light-weight and let migrated threads run.
602
         */
602
         */
603
        scheduler();
603
        scheduler();
604
    }
604
    }
605
    else {
605
    else {
606
        /*
606
        /*
607
         * We failed to migrate a single thread.
607
         * We failed to migrate a single thread.
608
         * Something more sophisticated should be done.
608
         * Something more sophisticated should be done.
609
         */
609
         */
610
        scheduler();
610
        scheduler();
611
    }
611
    }
612
       
612
       
613
    goto not_satisfied;
613
    goto not_satisfied;
614
 
614
 
615
satisfied:
615
satisfied:
616
    /*
616
    /*
617
     * Tell find_best_thread() to wake us up later again.
617
     * Tell find_best_thread() to wake us up later again.
618
     */
618
     */
619
    CPU->kcpulbstarted = 0;
619
    CPU->kcpulbstarted = 0;
620
    goto loop;
620
    goto loop;
621
}
621
}
622
 
622
 
623
#endif /* __SMP__ */
623
#endif /* __SMP__ */
624
 
624