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Rev | Author | Line No. | Line |
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1 | jermar | 1 | /* |
2071 | jermar | 2 | * Copyright (c) 2001-2007 Jakub Jermar |
1 | jermar | 3 | * All rights reserved. |
4 | * |
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5 | * Redistribution and use in source and binary forms, with or without |
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6 | * modification, are permitted provided that the following conditions |
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7 | * are met: |
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8 | * |
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9 | * - Redistributions of source code must retain the above copyright |
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10 | * notice, this list of conditions and the following disclaimer. |
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11 | * - Redistributions in binary form must reproduce the above copyright |
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12 | * notice, this list of conditions and the following disclaimer in the |
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13 | * documentation and/or other materials provided with the distribution. |
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14 | * - The name of the author may not be used to endorse or promote products |
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15 | * derived from this software without specific prior written permission. |
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16 | * |
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17 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR |
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18 | * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
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19 | * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. |
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20 | * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, |
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21 | * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT |
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22 | * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
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23 | * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
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24 | * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
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25 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF |
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26 | * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
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27 | */ |
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28 | |||
1757 | jermar | 29 | /** @addtogroup genericproc |
1702 | cejka | 30 | * @{ |
31 | */ |
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32 | |||
1248 | jermar | 33 | /** |
1702 | cejka | 34 | * @file |
1248 | jermar | 35 | * @brief Scheduler and load balancing. |
36 | * |
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1264 | jermar | 37 | * This file contains the scheduler and kcpulb kernel thread which |
1248 | jermar | 38 | * performs load-balancing of per-CPU run queues. |
39 | */ |
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40 | |||
1 | jermar | 41 | #include <proc/scheduler.h> |
42 | #include <proc/thread.h> |
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43 | #include <proc/task.h> |
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378 | jermar | 44 | #include <mm/frame.h> |
45 | #include <mm/page.h> |
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703 | jermar | 46 | #include <mm/as.h> |
2089 | decky | 47 | #include <time/timeout.h> |
1571 | jermar | 48 | #include <time/delay.h> |
378 | jermar | 49 | #include <arch/asm.h> |
50 | #include <arch/faddr.h> |
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2030 | decky | 51 | #include <arch/cycle.h> |
1104 | jermar | 52 | #include <atomic.h> |
378 | jermar | 53 | #include <synch/spinlock.h> |
1 | jermar | 54 | #include <config.h> |
55 | #include <context.h> |
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2089 | decky | 56 | #include <fpu_context.h> |
1 | jermar | 57 | #include <func.h> |
58 | #include <arch.h> |
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788 | jermar | 59 | #include <adt/list.h> |
68 | decky | 60 | #include <panic.h> |
378 | jermar | 61 | #include <cpu.h> |
195 | vana | 62 | #include <print.h> |
227 | jermar | 63 | #include <debug.h> |
1 | jermar | 64 | |
1187 | jermar | 65 | static void before_task_runs(void); |
66 | static void before_thread_runs(void); |
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67 | static void after_thread_ran(void); |
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898 | jermar | 68 | static void scheduler_separated_stack(void); |
195 | vana | 69 | |
898 | jermar | 70 | atomic_t nrdy; /**< Number of ready threads in the system. */ |
71 | |||
1187 | jermar | 72 | /** Carry out actions before new task runs. */ |
73 | void before_task_runs(void) |
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74 | { |
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75 | before_task_runs_arch(); |
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76 | } |
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77 | |||
897 | jermar | 78 | /** Take actions before new thread runs. |
107 | decky | 79 | * |
118 | jermar | 80 | * Perform actions that need to be |
81 | * taken before the newly selected |
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82 | * tread is passed control. |
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107 | decky | 83 | * |
827 | palkovsky | 84 | * THREAD->lock is locked on entry |
85 | * |
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107 | decky | 86 | */ |
52 | vana | 87 | void before_thread_runs(void) |
88 | { |
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309 | palkovsky | 89 | before_thread_runs_arch(); |
906 | palkovsky | 90 | #ifdef CONFIG_FPU_LAZY |
1882 | jermar | 91 | if(THREAD == CPU->fpu_owner) |
309 | palkovsky | 92 | fpu_enable(); |
93 | else |
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94 | fpu_disable(); |
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906 | palkovsky | 95 | #else |
309 | palkovsky | 96 | fpu_enable(); |
97 | if (THREAD->fpu_context_exists) |
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906 | palkovsky | 98 | fpu_context_restore(THREAD->saved_fpu_context); |
309 | palkovsky | 99 | else { |
906 | palkovsky | 100 | fpu_init(); |
1882 | jermar | 101 | THREAD->fpu_context_exists = 1; |
309 | palkovsky | 102 | } |
906 | palkovsky | 103 | #endif |
52 | vana | 104 | } |
105 | |||
898 | jermar | 106 | /** Take actions after THREAD had run. |
897 | jermar | 107 | * |
108 | * Perform actions that need to be |
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109 | * taken after the running thread |
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898 | jermar | 110 | * had been preempted by the scheduler. |
897 | jermar | 111 | * |
112 | * THREAD->lock is locked on entry |
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113 | * |
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114 | */ |
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115 | void after_thread_ran(void) |
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116 | { |
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117 | after_thread_ran_arch(); |
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118 | } |
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119 | |||
458 | decky | 120 | #ifdef CONFIG_FPU_LAZY |
309 | palkovsky | 121 | void scheduler_fpu_lazy_request(void) |
122 | { |
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907 | palkovsky | 123 | restart: |
309 | palkovsky | 124 | fpu_enable(); |
827 | palkovsky | 125 | spinlock_lock(&CPU->lock); |
126 | |||
127 | /* Save old context */ |
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309 | palkovsky | 128 | if (CPU->fpu_owner != NULL) { |
827 | palkovsky | 129 | spinlock_lock(&CPU->fpu_owner->lock); |
906 | palkovsky | 130 | fpu_context_save(CPU->fpu_owner->saved_fpu_context); |
309 | palkovsky | 131 | /* don't prevent migration */ |
1882 | jermar | 132 | CPU->fpu_owner->fpu_context_engaged = 0; |
827 | palkovsky | 133 | spinlock_unlock(&CPU->fpu_owner->lock); |
907 | palkovsky | 134 | CPU->fpu_owner = NULL; |
309 | palkovsky | 135 | } |
827 | palkovsky | 136 | |
137 | spinlock_lock(&THREAD->lock); |
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898 | jermar | 138 | if (THREAD->fpu_context_exists) { |
906 | palkovsky | 139 | fpu_context_restore(THREAD->saved_fpu_context); |
898 | jermar | 140 | } else { |
906 | palkovsky | 141 | /* Allocate FPU context */ |
142 | if (!THREAD->saved_fpu_context) { |
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143 | /* Might sleep */ |
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144 | spinlock_unlock(&THREAD->lock); |
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907 | palkovsky | 145 | spinlock_unlock(&CPU->lock); |
2067 | jermar | 146 | THREAD->saved_fpu_context = |
2118 | decky | 147 | (fpu_context_t *) slab_alloc(fpu_context_slab, 0); |
907 | palkovsky | 148 | /* We may have switched CPUs during slab_alloc */ |
149 | goto restart; |
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906 | palkovsky | 150 | } |
151 | fpu_init(); |
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1882 | jermar | 152 | THREAD->fpu_context_exists = 1; |
309 | palkovsky | 153 | } |
1882 | jermar | 154 | CPU->fpu_owner = THREAD; |
309 | palkovsky | 155 | THREAD->fpu_context_engaged = 1; |
898 | jermar | 156 | spinlock_unlock(&THREAD->lock); |
827 | palkovsky | 157 | |
158 | spinlock_unlock(&CPU->lock); |
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309 | palkovsky | 159 | } |
160 | #endif |
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52 | vana | 161 | |
107 | decky | 162 | /** Initialize scheduler |
163 | * |
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164 | * Initialize kernel scheduler. |
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165 | * |
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166 | */ |
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1 | jermar | 167 | void scheduler_init(void) |
168 | { |
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169 | } |
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170 | |||
107 | decky | 171 | /** Get thread to be scheduled |
172 | * |
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173 | * Get the optimal thread to be scheduled |
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109 | jermar | 174 | * according to thread accounting and scheduler |
107 | decky | 175 | * policy. |
176 | * |
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177 | * @return Thread to be scheduled. |
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178 | * |
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179 | */ |
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483 | jermar | 180 | static thread_t *find_best_thread(void) |
1 | jermar | 181 | { |
182 | thread_t *t; |
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183 | runq_t *r; |
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783 | palkovsky | 184 | int i; |
1 | jermar | 185 | |
227 | jermar | 186 | ASSERT(CPU != NULL); |
187 | |||
1 | jermar | 188 | loop: |
413 | jermar | 189 | interrupts_enable(); |
1 | jermar | 190 | |
783 | palkovsky | 191 | if (atomic_get(&CPU->nrdy) == 0) { |
1 | jermar | 192 | /* |
193 | * For there was nothing to run, the CPU goes to sleep |
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194 | * until a hardware interrupt or an IPI comes. |
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195 | * This improves energy saving and hyperthreading. |
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196 | */ |
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785 | jermar | 197 | |
198 | /* |
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199 | * An interrupt might occur right now and wake up a thread. |
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200 | * In such case, the CPU will continue to go to sleep |
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201 | * even though there is a runnable thread. |
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202 | */ |
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203 | |||
1 | jermar | 204 | cpu_sleep(); |
205 | goto loop; |
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206 | } |
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207 | |||
413 | jermar | 208 | interrupts_disable(); |
114 | jermar | 209 | |
2285 | jermar | 210 | for (i = 0; i < RQ_COUNT; i++) { |
15 | jermar | 211 | r = &CPU->rq[i]; |
1 | jermar | 212 | spinlock_lock(&r->lock); |
213 | if (r->n == 0) { |
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214 | /* |
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215 | * If this queue is empty, try a lower-priority queue. |
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216 | */ |
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217 | spinlock_unlock(&r->lock); |
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218 | continue; |
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219 | } |
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213 | jermar | 220 | |
783 | palkovsky | 221 | atomic_dec(&CPU->nrdy); |
475 | jermar | 222 | atomic_dec(&nrdy); |
1 | jermar | 223 | r->n--; |
224 | |||
225 | /* |
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226 | * Take the first thread from the queue. |
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227 | */ |
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228 | t = list_get_instance(r->rq_head.next, thread_t, rq_link); |
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229 | list_remove(&t->rq_link); |
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230 | |||
231 | spinlock_unlock(&r->lock); |
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232 | |||
233 | spinlock_lock(&t->lock); |
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15 | jermar | 234 | t->cpu = CPU; |
1 | jermar | 235 | |
2067 | jermar | 236 | t->ticks = us2ticks((i + 1) * 10000); |
898 | jermar | 237 | t->priority = i; /* correct rq index */ |
1 | jermar | 238 | |
239 | /* |
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1854 | jermar | 240 | * Clear the THREAD_FLAG_STOLEN flag so that t can be migrated |
241 | * when load balancing needs emerge. |
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1 | jermar | 242 | */ |
1854 | jermar | 243 | t->flags &= ~THREAD_FLAG_STOLEN; |
1 | jermar | 244 | spinlock_unlock(&t->lock); |
245 | |||
246 | return t; |
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247 | } |
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248 | goto loop; |
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249 | |||
250 | } |
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251 | |||
107 | decky | 252 | /** Prevent rq starvation |
253 | * |
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254 | * Prevent low priority threads from starving in rq's. |
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255 | * |
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256 | * When the function decides to relink rq's, it reconnects |
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257 | * respective pointers so that in result threads with 'pri' |
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1708 | jermar | 258 | * greater or equal start are moved to a higher-priority queue. |
107 | decky | 259 | * |
260 | * @param start Threshold priority. |
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261 | * |
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1 | jermar | 262 | */ |
452 | decky | 263 | static void relink_rq(int start) |
1 | jermar | 264 | { |
265 | link_t head; |
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266 | runq_t *r; |
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267 | int i, n; |
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268 | |||
269 | list_initialize(&head); |
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15 | jermar | 270 | spinlock_lock(&CPU->lock); |
271 | if (CPU->needs_relink > NEEDS_RELINK_MAX) { |
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2067 | jermar | 272 | for (i = start; i < RQ_COUNT - 1; i++) { |
1 | jermar | 273 | /* remember and empty rq[i + 1] */ |
15 | jermar | 274 | r = &CPU->rq[i + 1]; |
1 | jermar | 275 | spinlock_lock(&r->lock); |
276 | list_concat(&head, &r->rq_head); |
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277 | n = r->n; |
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278 | r->n = 0; |
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279 | spinlock_unlock(&r->lock); |
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280 | |||
281 | /* append rq[i + 1] to rq[i] */ |
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15 | jermar | 282 | r = &CPU->rq[i]; |
1 | jermar | 283 | spinlock_lock(&r->lock); |
284 | list_concat(&r->rq_head, &head); |
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285 | r->n += n; |
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286 | spinlock_unlock(&r->lock); |
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287 | } |
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15 | jermar | 288 | CPU->needs_relink = 0; |
1 | jermar | 289 | } |
784 | palkovsky | 290 | spinlock_unlock(&CPU->lock); |
1 | jermar | 291 | |
292 | } |
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293 | |||
898 | jermar | 294 | /** The scheduler |
295 | * |
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296 | * The thread scheduling procedure. |
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297 | * Passes control directly to |
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298 | * scheduler_separated_stack(). |
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299 | * |
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300 | */ |
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301 | void scheduler(void) |
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302 | { |
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303 | volatile ipl_t ipl; |
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107 | decky | 304 | |
898 | jermar | 305 | ASSERT(CPU != NULL); |
306 | |||
307 | ipl = interrupts_disable(); |
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308 | |||
309 | if (atomic_get(&haltstate)) |
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310 | halt(); |
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1007 | decky | 311 | |
898 | jermar | 312 | if (THREAD) { |
313 | spinlock_lock(&THREAD->lock); |
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2030 | decky | 314 | |
315 | /* Update thread accounting */ |
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316 | THREAD->cycles += get_cycle() - THREAD->last_cycle; |
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317 | |||
906 | palkovsky | 318 | #ifndef CONFIG_FPU_LAZY |
319 | fpu_context_save(THREAD->saved_fpu_context); |
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320 | #endif |
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898 | jermar | 321 | if (!context_save(&THREAD->saved_context)) { |
322 | /* |
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323 | * This is the place where threads leave scheduler(); |
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324 | */ |
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2030 | decky | 325 | |
326 | /* Save current CPU cycle */ |
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327 | THREAD->last_cycle = get_cycle(); |
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328 | |||
898 | jermar | 329 | spinlock_unlock(&THREAD->lock); |
330 | interrupts_restore(THREAD->saved_context.ipl); |
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1007 | decky | 331 | |
898 | jermar | 332 | return; |
333 | } |
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334 | |||
335 | /* |
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2067 | jermar | 336 | * Interrupt priority level of preempted thread is recorded |
337 | * here to facilitate scheduler() invocations from |
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338 | * interrupts_disable()'d code (e.g. waitq_sleep_timeout()). |
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898 | jermar | 339 | */ |
340 | THREAD->saved_context.ipl = ipl; |
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341 | } |
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342 | |||
343 | /* |
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344 | * Through the 'THE' structure, we keep track of THREAD, TASK, CPU, VM |
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345 | * and preemption counter. At this point THE could be coming either |
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346 | * from THREAD's or CPU's stack. |
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347 | */ |
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348 | the_copy(THE, (the_t *) CPU->stack); |
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349 | |||
350 | /* |
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351 | * We may not keep the old stack. |
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352 | * Reason: If we kept the old stack and got blocked, for instance, in |
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353 | * find_best_thread(), the old thread could get rescheduled by another |
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354 | * CPU and overwrite the part of its own stack that was also used by |
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355 | * the scheduler on this CPU. |
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356 | * |
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357 | * Moreover, we have to bypass the compiler-generated POP sequence |
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358 | * which is fooled by SP being set to the very top of the stack. |
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359 | * Therefore the scheduler() function continues in |
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360 | * scheduler_separated_stack(). |
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361 | */ |
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362 | context_save(&CPU->saved_context); |
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1854 | jermar | 363 | context_set(&CPU->saved_context, FADDR(scheduler_separated_stack), |
2087 | jermar | 364 | (uintptr_t) CPU->stack, CPU_STACK_SIZE); |
898 | jermar | 365 | context_restore(&CPU->saved_context); |
366 | /* not reached */ |
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367 | } |
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368 | |||
107 | decky | 369 | /** Scheduler stack switch wrapper |
370 | * |
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371 | * Second part of the scheduler() function |
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372 | * using new stack. Handling the actual context |
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373 | * switch to a new thread. |
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374 | * |
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787 | palkovsky | 375 | * Assume THREAD->lock is held. |
107 | decky | 376 | */ |
898 | jermar | 377 | void scheduler_separated_stack(void) |
1 | jermar | 378 | { |
379 | int priority; |
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2183 | jermar | 380 | DEADLOCK_PROBE_INIT(p_joinwq); |
381 | |||
227 | jermar | 382 | ASSERT(CPU != NULL); |
1007 | decky | 383 | |
15 | jermar | 384 | if (THREAD) { |
898 | jermar | 385 | /* must be run after the switch to scheduler stack */ |
897 | jermar | 386 | after_thread_ran(); |
387 | |||
15 | jermar | 388 | switch (THREAD->state) { |
1888 | jermar | 389 | case Running: |
125 | jermar | 390 | spinlock_unlock(&THREAD->lock); |
391 | thread_ready(THREAD); |
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392 | break; |
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1 | jermar | 393 | |
1888 | jermar | 394 | case Exiting: |
1571 | jermar | 395 | repeat: |
2040 | decky | 396 | if (THREAD->detached) { |
1571 | jermar | 397 | thread_destroy(THREAD); |
398 | } else { |
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399 | /* |
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2067 | jermar | 400 | * The thread structure is kept allocated until |
401 | * somebody calls thread_detach() on it. |
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1571 | jermar | 402 | */ |
403 | if (!spinlock_trylock(&THREAD->join_wq.lock)) { |
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404 | /* |
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405 | * Avoid deadlock. |
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406 | */ |
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407 | spinlock_unlock(&THREAD->lock); |
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2446 | jermar | 408 | delay(HZ); |
1571 | jermar | 409 | spinlock_lock(&THREAD->lock); |
2183 | jermar | 410 | DEADLOCK_PROBE(p_joinwq, |
411 | DEADLOCK_THRESHOLD); |
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1571 | jermar | 412 | goto repeat; |
413 | } |
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2310 | jermar | 414 | _waitq_wakeup_unsafe(&THREAD->join_wq, |
415 | WAKEUP_FIRST); |
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1571 | jermar | 416 | spinlock_unlock(&THREAD->join_wq.lock); |
417 | |||
2451 | jermar | 418 | THREAD->state = Lingering; |
1571 | jermar | 419 | spinlock_unlock(&THREAD->lock); |
420 | } |
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125 | jermar | 421 | break; |
787 | palkovsky | 422 | |
1888 | jermar | 423 | case Sleeping: |
125 | jermar | 424 | /* |
425 | * Prefer the thread after it's woken up. |
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426 | */ |
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413 | jermar | 427 | THREAD->priority = -1; |
1 | jermar | 428 | |
125 | jermar | 429 | /* |
2067 | jermar | 430 | * We need to release wq->lock which we locked in |
431 | * waitq_sleep(). Address of wq->lock is kept in |
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432 | * THREAD->sleep_queue. |
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125 | jermar | 433 | */ |
434 | spinlock_unlock(&THREAD->sleep_queue->lock); |
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1 | jermar | 435 | |
125 | jermar | 436 | /* |
2067 | jermar | 437 | * Check for possible requests for out-of-context |
438 | * invocation. |
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125 | jermar | 439 | */ |
440 | if (THREAD->call_me) { |
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441 | THREAD->call_me(THREAD->call_me_with); |
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442 | THREAD->call_me = NULL; |
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443 | THREAD->call_me_with = NULL; |
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444 | } |
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1 | jermar | 445 | |
125 | jermar | 446 | spinlock_unlock(&THREAD->lock); |
1 | jermar | 447 | |
125 | jermar | 448 | break; |
449 | |||
1888 | jermar | 450 | default: |
125 | jermar | 451 | /* |
452 | * Entering state is unexpected. |
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453 | */ |
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4339 | svoboda | 454 | panic("tid%" PRIu64 ": unexpected state %s.", |
3191 | svoboda | 455 | THREAD->tid, thread_states[THREAD->state]); |
125 | jermar | 456 | break; |
1 | jermar | 457 | } |
897 | jermar | 458 | |
15 | jermar | 459 | THREAD = NULL; |
1 | jermar | 460 | } |
198 | jermar | 461 | |
15 | jermar | 462 | THREAD = find_best_thread(); |
1 | jermar | 463 | |
15 | jermar | 464 | spinlock_lock(&THREAD->lock); |
413 | jermar | 465 | priority = THREAD->priority; |
15 | jermar | 466 | spinlock_unlock(&THREAD->lock); |
192 | jermar | 467 | |
1 | jermar | 468 | relink_rq(priority); |
469 | |||
470 | /* |
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2067 | jermar | 471 | * If both the old and the new task are the same, lots of work is |
472 | * avoided. |
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1 | jermar | 473 | */ |
15 | jermar | 474 | if (TASK != THREAD->task) { |
703 | jermar | 475 | as_t *as1 = NULL; |
476 | as_t *as2; |
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1 | jermar | 477 | |
15 | jermar | 478 | if (TASK) { |
479 | spinlock_lock(&TASK->lock); |
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703 | jermar | 480 | as1 = TASK->as; |
15 | jermar | 481 | spinlock_unlock(&TASK->lock); |
1 | jermar | 482 | } |
483 | |||
15 | jermar | 484 | spinlock_lock(&THREAD->task->lock); |
703 | jermar | 485 | as2 = THREAD->task->as; |
15 | jermar | 486 | spinlock_unlock(&THREAD->task->lock); |
1 | jermar | 487 | |
488 | /* |
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2067 | jermar | 489 | * Note that it is possible for two tasks to share one address |
490 | * space. |
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1 | jermar | 491 | */ |
703 | jermar | 492 | if (as1 != as2) { |
1 | jermar | 493 | /* |
703 | jermar | 494 | * Both tasks and address spaces are different. |
1 | jermar | 495 | * Replace the old one with the new one. |
496 | */ |
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823 | jermar | 497 | as_switch(as1, as2); |
1 | jermar | 498 | } |
906 | palkovsky | 499 | TASK = THREAD->task; |
1187 | jermar | 500 | before_task_runs(); |
1 | jermar | 501 | } |
502 | |||
1380 | jermar | 503 | spinlock_lock(&THREAD->lock); |
15 | jermar | 504 | THREAD->state = Running; |
1 | jermar | 505 | |
906 | palkovsky | 506 | #ifdef SCHEDULER_VERBOSE |
3191 | svoboda | 507 | printf("cpu%u: tid %" PRIu64 " (priority=%d, ticks=%" PRIu64 |
508 | ", nrdy=%ld)\n", CPU->id, THREAD->tid, THREAD->priority, |
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509 | THREAD->ticks, atomic_get(&CPU->nrdy)); |
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906 | palkovsky | 510 | #endif |
1 | jermar | 511 | |
213 | jermar | 512 | /* |
897 | jermar | 513 | * Some architectures provide late kernel PA2KA(identity) |
514 | * mapping in a page fault handler. However, the page fault |
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515 | * handler uses the kernel stack of the running thread and |
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516 | * therefore cannot be used to map it. The kernel stack, if |
||
517 | * necessary, is to be mapped in before_thread_runs(). This |
||
518 | * function must be executed before the switch to the new stack. |
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519 | */ |
||
520 | before_thread_runs(); |
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521 | |||
522 | /* |
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2067 | jermar | 523 | * Copy the knowledge of CPU, TASK, THREAD and preemption counter to |
524 | * thread's stack. |
||
213 | jermar | 525 | */ |
184 | jermar | 526 | the_copy(THE, (the_t *) THREAD->kstack); |
527 | |||
15 | jermar | 528 | context_restore(&THREAD->saved_context); |
1 | jermar | 529 | /* not reached */ |
530 | } |
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531 | |||
458 | decky | 532 | #ifdef CONFIG_SMP |
107 | decky | 533 | /** Load balancing thread |
534 | * |
||
535 | * SMP load balancing thread, supervising thread supplies |
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536 | * for the CPU it's wired to. |
||
537 | * |
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538 | * @param arg Generic thread argument (unused). |
||
539 | * |
||
1 | jermar | 540 | */ |
541 | void kcpulb(void *arg) |
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542 | { |
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543 | thread_t *t; |
||
2118 | decky | 544 | int count, average, j, k = 0; |
545 | unsigned int i; |
||
413 | jermar | 546 | ipl_t ipl; |
1 | jermar | 547 | |
1576 | jermar | 548 | /* |
549 | * Detach kcpulb as nobody will call thread_join_timeout() on it. |
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550 | */ |
||
551 | thread_detach(THREAD); |
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552 | |||
1 | jermar | 553 | loop: |
554 | /* |
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779 | jermar | 555 | * Work in 1s intervals. |
1 | jermar | 556 | */ |
779 | jermar | 557 | thread_sleep(1); |
1 | jermar | 558 | |
559 | not_satisfied: |
||
560 | /* |
||
561 | * Calculate the number of threads that will be migrated/stolen from |
||
562 | * other CPU's. Note that situation can have changed between two |
||
563 | * passes. Each time get the most up to date counts. |
||
564 | */ |
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784 | palkovsky | 565 | average = atomic_get(&nrdy) / config.cpu_active + 1; |
783 | palkovsky | 566 | count = average - atomic_get(&CPU->nrdy); |
1 | jermar | 567 | |
784 | palkovsky | 568 | if (count <= 0) |
1 | jermar | 569 | goto satisfied; |
570 | |||
571 | /* |
||
2067 | jermar | 572 | * Searching least priority queues on all CPU's first and most priority |
573 | * queues on all CPU's last. |
||
1 | jermar | 574 | */ |
2285 | jermar | 575 | for (j = RQ_COUNT - 1; j >= 0; j--) { |
2067 | jermar | 576 | for (i = 0; i < config.cpu_active; i++) { |
1 | jermar | 577 | link_t *l; |
578 | runq_t *r; |
||
579 | cpu_t *cpu; |
||
580 | |||
581 | cpu = &cpus[(i + k) % config.cpu_active]; |
||
582 | |||
583 | /* |
||
584 | * Not interested in ourselves. |
||
2067 | jermar | 585 | * Doesn't require interrupt disabling for kcpulb has |
586 | * THREAD_FLAG_WIRED. |
||
1 | jermar | 587 | */ |
15 | jermar | 588 | if (CPU == cpu) |
783 | palkovsky | 589 | continue; |
590 | if (atomic_get(&cpu->nrdy) <= average) |
||
591 | continue; |
||
1 | jermar | 592 | |
784 | palkovsky | 593 | ipl = interrupts_disable(); |
115 | jermar | 594 | r = &cpu->rq[j]; |
1 | jermar | 595 | spinlock_lock(&r->lock); |
596 | if (r->n == 0) { |
||
597 | spinlock_unlock(&r->lock); |
||
413 | jermar | 598 | interrupts_restore(ipl); |
1 | jermar | 599 | continue; |
600 | } |
||
601 | |||
602 | t = NULL; |
||
603 | l = r->rq_head.prev; /* search rq from the back */ |
||
604 | while (l != &r->rq_head) { |
||
605 | t = list_get_instance(l, thread_t, rq_link); |
||
606 | /* |
||
2067 | jermar | 607 | * We don't want to steal CPU-wired threads |
608 | * neither threads already stolen. The latter |
||
609 | * prevents threads from migrating between CPU's |
||
610 | * without ever being run. We don't want to |
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611 | * steal threads whose FPU context is still in |
||
612 | * CPU. |
||
73 | vana | 613 | */ |
1 | jermar | 614 | spinlock_lock(&t->lock); |
2067 | jermar | 615 | if ((!(t->flags & (THREAD_FLAG_WIRED | |
2285 | jermar | 616 | THREAD_FLAG_STOLEN))) && |
617 | (!(t->fpu_context_engaged))) { |
||
1 | jermar | 618 | /* |
619 | * Remove t from r. |
||
620 | */ |
||
621 | spinlock_unlock(&t->lock); |
||
622 | |||
783 | palkovsky | 623 | atomic_dec(&cpu->nrdy); |
475 | jermar | 624 | atomic_dec(&nrdy); |
1 | jermar | 625 | |
125 | jermar | 626 | r->n--; |
1 | jermar | 627 | list_remove(&t->rq_link); |
628 | |||
629 | break; |
||
630 | } |
||
631 | spinlock_unlock(&t->lock); |
||
632 | l = l->prev; |
||
633 | t = NULL; |
||
634 | } |
||
635 | spinlock_unlock(&r->lock); |
||
636 | |||
637 | if (t) { |
||
638 | /* |
||
639 | * Ready t on local CPU |
||
640 | */ |
||
641 | spinlock_lock(&t->lock); |
||
906 | palkovsky | 642 | #ifdef KCPULB_VERBOSE |
3191 | svoboda | 643 | printf("kcpulb%u: TID %" PRIu64 " -> cpu%u, " |
644 | "nrdy=%ld, avg=%ld\n", CPU->id, t->tid, |
||
645 | CPU->id, atomic_get(&CPU->nrdy), |
||
2087 | jermar | 646 | atomic_get(&nrdy) / config.cpu_active); |
906 | palkovsky | 647 | #endif |
1854 | jermar | 648 | t->flags |= THREAD_FLAG_STOLEN; |
1115 | jermar | 649 | t->state = Entering; |
1 | jermar | 650 | spinlock_unlock(&t->lock); |
651 | |||
652 | thread_ready(t); |
||
653 | |||
413 | jermar | 654 | interrupts_restore(ipl); |
1 | jermar | 655 | |
656 | if (--count == 0) |
||
657 | goto satisfied; |
||
658 | |||
659 | /* |
||
2067 | jermar | 660 | * We are not satisfied yet, focus on another |
661 | * CPU next time. |
||
1 | jermar | 662 | */ |
663 | k++; |
||
664 | |||
665 | continue; |
||
666 | } |
||
413 | jermar | 667 | interrupts_restore(ipl); |
1 | jermar | 668 | } |
669 | } |
||
670 | |||
783 | palkovsky | 671 | if (atomic_get(&CPU->nrdy)) { |
1 | jermar | 672 | /* |
673 | * Be a little bit light-weight and let migrated threads run. |
||
674 | */ |
||
675 | scheduler(); |
||
779 | jermar | 676 | } else { |
1 | jermar | 677 | /* |
678 | * We failed to migrate a single thread. |
||
779 | jermar | 679 | * Give up this turn. |
1 | jermar | 680 | */ |
779 | jermar | 681 | goto loop; |
1 | jermar | 682 | } |
683 | |||
684 | goto not_satisfied; |
||
125 | jermar | 685 | |
1 | jermar | 686 | satisfied: |
687 | goto loop; |
||
688 | } |
||
689 | |||
458 | decky | 690 | #endif /* CONFIG_SMP */ |
775 | palkovsky | 691 | |
692 | |||
693 | /** Print information about threads & scheduler queues */ |
||
694 | void sched_print_list(void) |
||
695 | { |
||
696 | ipl_t ipl; |
||
2118 | decky | 697 | unsigned int cpu, i; |
775 | palkovsky | 698 | runq_t *r; |
699 | thread_t *t; |
||
700 | link_t *cur; |
||
701 | |||
702 | /* We are going to mess with scheduler structures, |
||
703 | * let's not be interrupted */ |
||
704 | ipl = interrupts_disable(); |
||
2118 | decky | 705 | for (cpu = 0; cpu < config.cpu_count; cpu++) { |
898 | jermar | 706 | |
775 | palkovsky | 707 | if (!cpus[cpu].active) |
708 | continue; |
||
898 | jermar | 709 | |
775 | palkovsky | 710 | spinlock_lock(&cpus[cpu].lock); |
4691 | svoboda | 711 | printf("cpu%u: address=%p, nrdy=%ld, needs_relink=%" PRIs "\n", |
2087 | jermar | 712 | cpus[cpu].id, &cpus[cpu], atomic_get(&cpus[cpu].nrdy), |
713 | cpus[cpu].needs_relink); |
||
775 | palkovsky | 714 | |
2067 | jermar | 715 | for (i = 0; i < RQ_COUNT; i++) { |
775 | palkovsky | 716 | r = &cpus[cpu].rq[i]; |
717 | spinlock_lock(&r->lock); |
||
718 | if (!r->n) { |
||
719 | spinlock_unlock(&r->lock); |
||
720 | continue; |
||
721 | } |
||
3149 | svoboda | 722 | printf("\trq[%u]: ", i); |
2067 | jermar | 723 | for (cur = r->rq_head.next; cur != &r->rq_head; |
724 | cur = cur->next) { |
||
775 | palkovsky | 725 | t = list_get_instance(cur, thread_t, rq_link); |
3149 | svoboda | 726 | printf("%" PRIu64 "(%s) ", t->tid, |
2087 | jermar | 727 | thread_states[t->state]); |
775 | palkovsky | 728 | } |
729 | printf("\n"); |
||
730 | spinlock_unlock(&r->lock); |
||
731 | } |
||
732 | spinlock_unlock(&cpus[cpu].lock); |
||
733 | } |
||
734 | |||
735 | interrupts_restore(ipl); |
||
736 | } |
||
1702 | cejka | 737 | |
1757 | jermar | 738 | /** @} |
1702 | cejka | 739 | */ |