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Rev | Author | Line No. | Line |
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1 | jermar | 1 | /* |
2 | * Copyright (C) 2001-2004 Jakub Jermar |
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3 | * All rights reserved. |
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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 | |||
29 | #include <proc/scheduler.h> |
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30 | #include <proc/thread.h> |
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31 | #include <proc/task.h> |
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32 | #include <cpu.h> |
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33 | #include <mm/vm.h> |
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34 | #include <config.h> |
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35 | #include <context.h> |
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36 | #include <func.h> |
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37 | #include <arch.h> |
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38 | #include <arch/asm.h> |
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39 | #include <list.h> |
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68 | decky | 40 | #include <panic.h> |
1 | jermar | 41 | #include <typedefs.h> |
42 | #include <mm/page.h> |
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43 | #include <synch/spinlock.h> |
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76 | jermar | 44 | #include <arch/faddr.h> |
111 | palkovsky | 45 | #include <arch/atomic.h> |
1 | jermar | 46 | |
47 | volatile int nrdy; |
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48 | |||
107 | decky | 49 | |
50 | /** Initialize context switching |
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51 | * |
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52 | * Initialize context switching and lazy FPU |
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53 | * context switching. |
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54 | * |
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55 | */ |
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52 | vana | 56 | void before_thread_runs(void) |
57 | { |
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58 | before_thread_runs_arch(); |
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57 | vana | 59 | fpu_context_restore(&(THREAD->saved_fpu_context)); |
52 | vana | 60 | } |
61 | |||
62 | |||
107 | decky | 63 | /** Initialize scheduler |
64 | * |
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65 | * Initialize kernel scheduler. |
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66 | * |
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67 | */ |
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1 | jermar | 68 | void scheduler_init(void) |
69 | { |
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70 | } |
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71 | |||
107 | decky | 72 | |
73 | /** Get thread to be scheduled |
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74 | * |
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75 | * Get the optimal thread to be scheduled |
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109 | jermar | 76 | * according to thread accounting and scheduler |
107 | decky | 77 | * policy. |
78 | * |
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79 | * @return Thread to be scheduled. |
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80 | * |
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81 | */ |
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1 | jermar | 82 | struct thread *find_best_thread(void) |
83 | { |
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84 | thread_t *t; |
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85 | runq_t *r; |
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86 | int i, n; |
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87 | |||
88 | loop: |
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89 | cpu_priority_high(); |
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90 | |||
15 | jermar | 91 | spinlock_lock(&CPU->lock); |
92 | n = CPU->nrdy; |
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93 | spinlock_unlock(&CPU->lock); |
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1 | jermar | 94 | |
95 | cpu_priority_low(); |
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96 | |||
97 | if (n == 0) { |
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98 | #ifdef __SMP__ |
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99 | /* |
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100 | * If the load balancing thread is not running, wake it up and |
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101 | * set CPU-private flag that the kcpulb has been started. |
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102 | */ |
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15 | jermar | 103 | if (test_and_set(&CPU->kcpulbstarted) == 0) { |
104 | waitq_wakeup(&CPU->kcpulb_wq, 0); |
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1 | jermar | 105 | goto loop; |
106 | } |
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107 | #endif /* __SMP__ */ |
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108 | |||
109 | /* |
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110 | * For there was nothing to run, the CPU goes to sleep |
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111 | * until a hardware interrupt or an IPI comes. |
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112 | * This improves energy saving and hyperthreading. |
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113 | * On the other hand, several hardware interrupts can be ignored. |
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114 | */ |
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115 | cpu_sleep(); |
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116 | goto loop; |
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117 | } |
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118 | |||
119 | cpu_priority_high(); |
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120 | |||
121 | for (i = 0; i<RQ_COUNT; i++) { |
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15 | jermar | 122 | r = &CPU->rq[i]; |
1 | jermar | 123 | spinlock_lock(&r->lock); |
124 | if (r->n == 0) { |
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125 | /* |
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126 | * If this queue is empty, try a lower-priority queue. |
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127 | */ |
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128 | spinlock_unlock(&r->lock); |
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129 | continue; |
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130 | } |
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131 | |||
111 | palkovsky | 132 | atomic_dec(&nrdy); |
1 | jermar | 133 | |
15 | jermar | 134 | spinlock_lock(&CPU->lock); |
135 | CPU->nrdy--; |
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136 | spinlock_unlock(&CPU->lock); |
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1 | jermar | 137 | |
138 | r->n--; |
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139 | |||
140 | /* |
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141 | * Take the first thread from the queue. |
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142 | */ |
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143 | t = list_get_instance(r->rq_head.next, thread_t, rq_link); |
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144 | list_remove(&t->rq_link); |
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145 | |||
146 | spinlock_unlock(&r->lock); |
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147 | |||
148 | spinlock_lock(&t->lock); |
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15 | jermar | 149 | t->cpu = CPU; |
1 | jermar | 150 | |
151 | t->ticks = us2ticks((i+1)*10000); |
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152 | t->pri = i; /* eventually correct rq index */ |
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153 | |||
154 | /* |
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155 | * Clear the X_STOLEN flag so that t can be migrated when load balancing needs emerge. |
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156 | */ |
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157 | t->flags &= ~X_STOLEN; |
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158 | spinlock_unlock(&t->lock); |
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159 | |||
160 | return t; |
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161 | } |
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162 | goto loop; |
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163 | |||
164 | } |
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165 | |||
107 | decky | 166 | |
167 | /** Prevent rq starvation |
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168 | * |
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169 | * Prevent low priority threads from starving in rq's. |
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170 | * |
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171 | * When the function decides to relink rq's, it reconnects |
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172 | * respective pointers so that in result threads with 'pri' |
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173 | * greater or equal 'start' are moved to a higher-priority queue. |
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174 | * |
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175 | * @param start Threshold priority. |
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176 | * |
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1 | jermar | 177 | */ |
178 | void relink_rq(int start) |
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179 | { |
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180 | link_t head; |
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181 | runq_t *r; |
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182 | int i, n; |
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183 | |||
184 | list_initialize(&head); |
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15 | jermar | 185 | spinlock_lock(&CPU->lock); |
186 | if (CPU->needs_relink > NEEDS_RELINK_MAX) { |
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1 | jermar | 187 | for (i = start; i<RQ_COUNT-1; i++) { |
188 | /* remember and empty rq[i + 1] */ |
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15 | jermar | 189 | r = &CPU->rq[i + 1]; |
1 | jermar | 190 | spinlock_lock(&r->lock); |
191 | list_concat(&head, &r->rq_head); |
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192 | n = r->n; |
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193 | r->n = 0; |
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194 | spinlock_unlock(&r->lock); |
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195 | |||
196 | /* append rq[i + 1] to rq[i] */ |
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15 | jermar | 197 | r = &CPU->rq[i]; |
1 | jermar | 198 | spinlock_lock(&r->lock); |
199 | list_concat(&r->rq_head, &head); |
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200 | r->n += n; |
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201 | spinlock_unlock(&r->lock); |
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202 | } |
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15 | jermar | 203 | CPU->needs_relink = 0; |
1 | jermar | 204 | } |
15 | jermar | 205 | spinlock_unlock(&CPU->lock); |
1 | jermar | 206 | |
207 | } |
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208 | |||
107 | decky | 209 | |
210 | /** The scheduler |
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211 | * |
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212 | * The thread scheduling procedure. |
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213 | * |
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1 | jermar | 214 | */ |
215 | void scheduler(void) |
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216 | { |
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217 | volatile pri_t pri; |
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218 | |||
219 | pri = cpu_priority_high(); |
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220 | |||
221 | if (haltstate) |
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222 | halt(); |
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223 | |||
15 | jermar | 224 | if (THREAD) { |
225 | spinlock_lock(&THREAD->lock); |
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57 | vana | 226 | fpu_context_save(&(THREAD->saved_fpu_context)); |
15 | jermar | 227 | if (!context_save(&THREAD->saved_context)) { |
1 | jermar | 228 | /* |
229 | * This is the place where threads leave scheduler(); |
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230 | */ |
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22 | jermar | 231 | before_thread_runs(); |
15 | jermar | 232 | spinlock_unlock(&THREAD->lock); |
233 | cpu_priority_restore(THREAD->saved_context.pri); |
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1 | jermar | 234 | return; |
235 | } |
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15 | jermar | 236 | THREAD->saved_context.pri = pri; |
1 | jermar | 237 | } |
238 | |||
239 | /* |
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240 | * We may not keep the old stack. |
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241 | * Reason: If we kept the old stack and got blocked, for instance, in |
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242 | * find_best_thread(), the old thread could get rescheduled by another |
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243 | * CPU and overwrite the part of its own stack that was also used by |
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244 | * the scheduler on this CPU. |
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245 | * |
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246 | * Moreover, we have to bypass the compiler-generated POP sequence |
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247 | * which is fooled by SP being set to the very top of the stack. |
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248 | * Therefore the scheduler() function continues in |
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249 | * scheduler_separated_stack(). |
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250 | */ |
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15 | jermar | 251 | context_save(&CPU->saved_context); |
97 | jermar | 252 | context_set(&CPU->saved_context, FADDR(scheduler_separated_stack), CPU->stack, CPU_STACK_SIZE); |
15 | jermar | 253 | context_restore(&CPU->saved_context); |
1 | jermar | 254 | /* not reached */ |
255 | } |
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256 | |||
107 | decky | 257 | |
258 | /** Scheduler stack switch wrapper |
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259 | * |
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260 | * Second part of the scheduler() function |
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261 | * using new stack. Handling the actual context |
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262 | * switch to a new thread. |
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263 | * |
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264 | */ |
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1 | jermar | 265 | void scheduler_separated_stack(void) |
266 | { |
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267 | int priority; |
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268 | |||
15 | jermar | 269 | if (THREAD) { |
270 | switch (THREAD->state) { |
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1 | jermar | 271 | case Running: |
15 | jermar | 272 | THREAD->state = Ready; |
273 | spinlock_unlock(&THREAD->lock); |
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274 | thread_ready(THREAD); |
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1 | jermar | 275 | break; |
276 | |||
277 | case Exiting: |
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15 | jermar | 278 | frame_free((__address) THREAD->kstack); |
279 | if (THREAD->ustack) { |
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280 | frame_free((__address) THREAD->ustack); |
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1 | jermar | 281 | } |
282 | |||
283 | /* |
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284 | * Detach from the containing task. |
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285 | */ |
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15 | jermar | 286 | spinlock_lock(&TASK->lock); |
287 | list_remove(&THREAD->th_link); |
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288 | spinlock_unlock(&TASK->lock); |
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1 | jermar | 289 | |
15 | jermar | 290 | spinlock_unlock(&THREAD->lock); |
1 | jermar | 291 | |
292 | spinlock_lock(&threads_lock); |
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15 | jermar | 293 | list_remove(&THREAD->threads_link); |
1 | jermar | 294 | spinlock_unlock(&threads_lock); |
73 | vana | 295 | |
99 | jermar | 296 | spinlock_lock(&CPU->lock); |
297 | if(CPU->fpu_owner==THREAD) CPU->fpu_owner=NULL; |
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298 | spinlock_unlock(&CPU->lock); |
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73 | vana | 299 | |
1 | jermar | 300 | |
15 | jermar | 301 | free(THREAD); |
1 | jermar | 302 | |
303 | break; |
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304 | |||
305 | case Sleeping: |
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306 | /* |
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307 | * Prefer the thread after it's woken up. |
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308 | */ |
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15 | jermar | 309 | THREAD->pri = -1; |
1 | jermar | 310 | |
311 | /* |
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312 | * We need to release wq->lock which we locked in waitq_sleep(). |
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15 | jermar | 313 | * Address of wq->lock is kept in THREAD->sleep_queue. |
1 | jermar | 314 | */ |
15 | jermar | 315 | spinlock_unlock(&THREAD->sleep_queue->lock); |
1 | jermar | 316 | |
317 | /* |
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318 | * Check for possible requests for out-of-context invocation. |
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319 | */ |
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15 | jermar | 320 | if (THREAD->call_me) { |
321 | THREAD->call_me(THREAD->call_me_with); |
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322 | THREAD->call_me = NULL; |
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323 | THREAD->call_me_with = NULL; |
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1 | jermar | 324 | } |
325 | |||
15 | jermar | 326 | spinlock_unlock(&THREAD->lock); |
1 | jermar | 327 | |
328 | break; |
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329 | |||
330 | default: |
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331 | /* |
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332 | * Entering state is unexpected. |
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333 | */ |
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15 | jermar | 334 | panic("tid%d: unexpected state %s\n", THREAD->tid, thread_states[THREAD->state]); |
1 | jermar | 335 | break; |
336 | } |
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15 | jermar | 337 | THREAD = NULL; |
1 | jermar | 338 | } |
339 | |||
15 | jermar | 340 | THREAD = find_best_thread(); |
1 | jermar | 341 | |
15 | jermar | 342 | spinlock_lock(&THREAD->lock); |
343 | priority = THREAD->pri; |
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344 | spinlock_unlock(&THREAD->lock); |
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1 | jermar | 345 | |
346 | relink_rq(priority); |
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347 | |||
15 | jermar | 348 | spinlock_lock(&THREAD->lock); |
1 | jermar | 349 | |
350 | /* |
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351 | * If both the old and the new task are the same, lots of work is avoided. |
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352 | */ |
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15 | jermar | 353 | if (TASK != THREAD->task) { |
1 | jermar | 354 | vm_t *m1 = NULL; |
355 | vm_t *m2; |
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356 | |||
15 | jermar | 357 | if (TASK) { |
358 | spinlock_lock(&TASK->lock); |
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359 | m1 = TASK->vm; |
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360 | spinlock_unlock(&TASK->lock); |
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1 | jermar | 361 | } |
362 | |||
15 | jermar | 363 | spinlock_lock(&THREAD->task->lock); |
364 | m2 = THREAD->task->vm; |
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365 | spinlock_unlock(&THREAD->task->lock); |
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1 | jermar | 366 | |
367 | /* |
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368 | * Note that it is possible for two tasks to share one vm mapping. |
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369 | */ |
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370 | if (m1 != m2) { |
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371 | /* |
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372 | * Both tasks and vm mappings are different. |
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373 | * Replace the old one with the new one. |
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374 | */ |
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375 | if (m1) { |
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376 | vm_uninstall(m1); |
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377 | } |
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378 | vm_install(m2); |
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379 | } |
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15 | jermar | 380 | TASK = THREAD->task; |
1 | jermar | 381 | } |
382 | |||
15 | jermar | 383 | THREAD->state = Running; |
1 | jermar | 384 | |
385 | #ifdef SCHEDULER_VERBOSE |
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15 | jermar | 386 | printf("cpu%d: tid %d (pri=%d,ticks=%d,nrdy=%d)\n", CPU->id, THREAD->tid, THREAD->pri, THREAD->ticks, CPU->nrdy); |
1 | jermar | 387 | #endif |
388 | |||
15 | jermar | 389 | context_restore(&THREAD->saved_context); |
1 | jermar | 390 | /* not reached */ |
391 | } |
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392 | |||
107 | decky | 393 | |
1 | jermar | 394 | #ifdef __SMP__ |
107 | decky | 395 | /** Load balancing thread |
396 | * |
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397 | * SMP load balancing thread, supervising thread supplies |
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398 | * for the CPU it's wired to. |
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399 | * |
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400 | * @param arg Generic thread argument (unused). |
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401 | * |
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1 | jermar | 402 | */ |
403 | void kcpulb(void *arg) |
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404 | { |
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405 | thread_t *t; |
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406 | int count, i, j, k = 0; |
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407 | pri_t pri; |
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408 | |||
409 | loop: |
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410 | /* |
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411 | * Sleep until there's some work to do. |
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412 | */ |
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15 | jermar | 413 | waitq_sleep(&CPU->kcpulb_wq); |
1 | jermar | 414 | |
415 | not_satisfied: |
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416 | /* |
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417 | * Calculate the number of threads that will be migrated/stolen from |
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418 | * other CPU's. Note that situation can have changed between two |
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419 | * passes. Each time get the most up to date counts. |
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420 | */ |
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421 | pri = cpu_priority_high(); |
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15 | jermar | 422 | spinlock_lock(&CPU->lock); |
1 | jermar | 423 | count = nrdy / config.cpu_active; |
15 | jermar | 424 | count -= CPU->nrdy; |
425 | spinlock_unlock(&CPU->lock); |
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1 | jermar | 426 | cpu_priority_restore(pri); |
427 | |||
428 | if (count <= 0) |
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429 | goto satisfied; |
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430 | |||
431 | /* |
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432 | * Searching least priority queues on all CPU's first and most priority queues on all CPU's last. |
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433 | */ |
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434 | for (j=RQ_COUNT-1; j >= 0; j--) { |
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435 | for (i=0; i < config.cpu_active; i++) { |
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436 | link_t *l; |
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437 | runq_t *r; |
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438 | cpu_t *cpu; |
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439 | |||
440 | cpu = &cpus[(i + k) % config.cpu_active]; |
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441 | r = &cpu->rq[j]; |
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442 | |||
443 | /* |
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444 | * Not interested in ourselves. |
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445 | * Doesn't require interrupt disabling for kcpulb is X_WIRED. |
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446 | */ |
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15 | jermar | 447 | if (CPU == cpu) |
1 | jermar | 448 | continue; |
449 | |||
450 | restart: pri = cpu_priority_high(); |
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451 | spinlock_lock(&r->lock); |
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452 | if (r->n == 0) { |
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453 | spinlock_unlock(&r->lock); |
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454 | cpu_priority_restore(pri); |
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455 | continue; |
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456 | } |
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457 | |||
458 | t = NULL; |
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459 | l = r->rq_head.prev; /* search rq from the back */ |
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460 | while (l != &r->rq_head) { |
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461 | t = list_get_instance(l, thread_t, rq_link); |
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462 | /* |
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463 | * We don't want to steal CPU-wired threads neither threads already stolen. |
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464 | * The latter prevents threads from migrating between CPU's without ever being run. |
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73 | vana | 465 | * We don't want to steal threads whose FPU context is still in CPU |
466 | */ |
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1 | jermar | 467 | spinlock_lock(&t->lock); |
73 | vana | 468 | if ( (!(t->flags & (X_WIRED | X_STOLEN))) && (!(t->fpu_context_engaged)) ) { |
1 | jermar | 469 | /* |
470 | * Remove t from r. |
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471 | */ |
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472 | |||
473 | spinlock_unlock(&t->lock); |
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474 | |||
475 | /* |
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476 | * Here we have to avoid deadlock with relink_rq(), |
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477 | * because it locks cpu and r in a different order than we do. |
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478 | */ |
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479 | if (!spinlock_trylock(&cpu->lock)) { |
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480 | /* Release all locks and try again. */ |
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481 | spinlock_unlock(&r->lock); |
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482 | cpu_priority_restore(pri); |
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483 | goto restart; |
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484 | } |
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485 | cpu->nrdy--; |
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486 | spinlock_unlock(&cpu->lock); |
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487 | |||
111 | palkovsky | 488 | atomic_dec(&nrdy); |
1 | jermar | 489 | |
490 | r->n--; |
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491 | list_remove(&t->rq_link); |
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492 | |||
493 | break; |
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494 | } |
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495 | spinlock_unlock(&t->lock); |
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496 | l = l->prev; |
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497 | t = NULL; |
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498 | } |
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499 | spinlock_unlock(&r->lock); |
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500 | |||
501 | if (t) { |
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502 | /* |
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503 | * Ready t on local CPU |
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504 | */ |
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505 | spinlock_lock(&t->lock); |
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506 | #ifdef KCPULB_VERBOSE |
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15 | jermar | 507 | 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 | 508 | #endif |
509 | t->flags |= X_STOLEN; |
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510 | spinlock_unlock(&t->lock); |
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511 | |||
512 | thread_ready(t); |
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513 | |||
514 | cpu_priority_restore(pri); |
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515 | |||
516 | if (--count == 0) |
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517 | goto satisfied; |
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518 | |||
519 | /* |
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520 | * We are not satisfied yet, focus on another CPU next time. |
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521 | */ |
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522 | k++; |
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523 | |||
524 | continue; |
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525 | } |
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526 | cpu_priority_restore(pri); |
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527 | } |
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528 | } |
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529 | |||
15 | jermar | 530 | if (CPU->nrdy) { |
1 | jermar | 531 | /* |
532 | * Be a little bit light-weight and let migrated threads run. |
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533 | */ |
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534 | scheduler(); |
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535 | } |
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536 | else { |
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537 | /* |
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538 | * We failed to migrate a single thread. |
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539 | * Something more sophisticated should be done. |
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540 | */ |
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541 | scheduler(); |
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542 | } |
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543 | |||
544 | goto not_satisfied; |
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545 | |||
546 | satisfied: |
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547 | /* |
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548 | * Tell find_best_thread() to wake us up later again. |
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549 | */ |
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15 | jermar | 550 | CPU->kcpulbstarted = 0; |
1 | jermar | 551 | goto loop; |
552 | } |
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553 | |||
554 | #endif /* __SMP__ */ |