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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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114 | jermar | 120 | |
121 | i = 0; |
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122 | retry: |
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123 | for (; i<RQ_COUNT; i++) { |
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15 | jermar | 124 | r = &CPU->rq[i]; |
1 | jermar | 125 | spinlock_lock(&r->lock); |
126 | if (r->n == 0) { |
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127 | /* |
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128 | * If this queue is empty, try a lower-priority queue. |
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129 | */ |
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130 | spinlock_unlock(&r->lock); |
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131 | continue; |
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132 | } |
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133 | |||
114 | jermar | 134 | /* avoid deadlock with relink_rq */ |
135 | if (!spinlock_trylock(&CPU->lock)) { |
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136 | /* |
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137 | * Unlock r and try again. |
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138 | */ |
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139 | spinlock_unlock(&r->lock); |
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140 | goto retry; |
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141 | } |
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15 | jermar | 142 | CPU->nrdy--; |
143 | spinlock_unlock(&CPU->lock); |
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1 | jermar | 144 | |
114 | jermar | 145 | atomic_dec(&nrdy); |
1 | jermar | 146 | r->n--; |
147 | |||
148 | /* |
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149 | * Take the first thread from the queue. |
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150 | */ |
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151 | t = list_get_instance(r->rq_head.next, thread_t, rq_link); |
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152 | list_remove(&t->rq_link); |
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153 | |||
154 | spinlock_unlock(&r->lock); |
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155 | |||
156 | spinlock_lock(&t->lock); |
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15 | jermar | 157 | t->cpu = CPU; |
1 | jermar | 158 | |
159 | t->ticks = us2ticks((i+1)*10000); |
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160 | t->pri = i; /* eventually correct rq index */ |
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161 | |||
162 | /* |
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163 | * Clear the X_STOLEN flag so that t can be migrated when load balancing needs emerge. |
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164 | */ |
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165 | t->flags &= ~X_STOLEN; |
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166 | spinlock_unlock(&t->lock); |
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167 | |||
168 | return t; |
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169 | } |
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170 | goto loop; |
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171 | |||
172 | } |
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173 | |||
107 | decky | 174 | |
175 | /** Prevent rq starvation |
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176 | * |
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177 | * Prevent low priority threads from starving in rq's. |
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178 | * |
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179 | * When the function decides to relink rq's, it reconnects |
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180 | * respective pointers so that in result threads with 'pri' |
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181 | * greater or equal 'start' are moved to a higher-priority queue. |
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182 | * |
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183 | * @param start Threshold priority. |
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184 | * |
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1 | jermar | 185 | */ |
186 | void relink_rq(int start) |
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187 | { |
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188 | link_t head; |
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189 | runq_t *r; |
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190 | int i, n; |
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191 | |||
192 | list_initialize(&head); |
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15 | jermar | 193 | spinlock_lock(&CPU->lock); |
194 | if (CPU->needs_relink > NEEDS_RELINK_MAX) { |
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1 | jermar | 195 | for (i = start; i<RQ_COUNT-1; i++) { |
196 | /* remember and empty rq[i + 1] */ |
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15 | jermar | 197 | r = &CPU->rq[i + 1]; |
1 | jermar | 198 | spinlock_lock(&r->lock); |
199 | list_concat(&head, &r->rq_head); |
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200 | n = r->n; |
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201 | r->n = 0; |
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202 | spinlock_unlock(&r->lock); |
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203 | |||
204 | /* append rq[i + 1] to rq[i] */ |
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15 | jermar | 205 | r = &CPU->rq[i]; |
1 | jermar | 206 | spinlock_lock(&r->lock); |
207 | list_concat(&r->rq_head, &head); |
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208 | r->n += n; |
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209 | spinlock_unlock(&r->lock); |
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210 | } |
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15 | jermar | 211 | CPU->needs_relink = 0; |
1 | jermar | 212 | } |
15 | jermar | 213 | spinlock_unlock(&CPU->lock); |
1 | jermar | 214 | |
215 | } |
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216 | |||
107 | decky | 217 | |
218 | /** The scheduler |
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219 | * |
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220 | * The thread scheduling procedure. |
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221 | * |
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1 | jermar | 222 | */ |
223 | void scheduler(void) |
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224 | { |
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225 | volatile pri_t pri; |
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226 | |||
227 | pri = cpu_priority_high(); |
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228 | |||
229 | if (haltstate) |
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230 | halt(); |
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231 | |||
15 | jermar | 232 | if (THREAD) { |
233 | spinlock_lock(&THREAD->lock); |
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57 | vana | 234 | fpu_context_save(&(THREAD->saved_fpu_context)); |
15 | jermar | 235 | if (!context_save(&THREAD->saved_context)) { |
1 | jermar | 236 | /* |
237 | * This is the place where threads leave scheduler(); |
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238 | */ |
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22 | jermar | 239 | before_thread_runs(); |
15 | jermar | 240 | spinlock_unlock(&THREAD->lock); |
241 | cpu_priority_restore(THREAD->saved_context.pri); |
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1 | jermar | 242 | return; |
243 | } |
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15 | jermar | 244 | THREAD->saved_context.pri = pri; |
1 | jermar | 245 | } |
246 | |||
247 | /* |
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248 | * We may not keep the old stack. |
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249 | * Reason: If we kept the old stack and got blocked, for instance, in |
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250 | * find_best_thread(), the old thread could get rescheduled by another |
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251 | * CPU and overwrite the part of its own stack that was also used by |
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252 | * the scheduler on this CPU. |
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253 | * |
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254 | * Moreover, we have to bypass the compiler-generated POP sequence |
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255 | * which is fooled by SP being set to the very top of the stack. |
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256 | * Therefore the scheduler() function continues in |
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257 | * scheduler_separated_stack(). |
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258 | */ |
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15 | jermar | 259 | context_save(&CPU->saved_context); |
97 | jermar | 260 | context_set(&CPU->saved_context, FADDR(scheduler_separated_stack), CPU->stack, CPU_STACK_SIZE); |
15 | jermar | 261 | context_restore(&CPU->saved_context); |
1 | jermar | 262 | /* not reached */ |
263 | } |
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264 | |||
107 | decky | 265 | |
266 | /** Scheduler stack switch wrapper |
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267 | * |
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268 | * Second part of the scheduler() function |
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269 | * using new stack. Handling the actual context |
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270 | * switch to a new thread. |
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271 | * |
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272 | */ |
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1 | jermar | 273 | void scheduler_separated_stack(void) |
274 | { |
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275 | int priority; |
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276 | |||
15 | jermar | 277 | if (THREAD) { |
278 | switch (THREAD->state) { |
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1 | jermar | 279 | case Running: |
15 | jermar | 280 | THREAD->state = Ready; |
281 | spinlock_unlock(&THREAD->lock); |
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282 | thread_ready(THREAD); |
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1 | jermar | 283 | break; |
284 | |||
285 | case Exiting: |
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15 | jermar | 286 | frame_free((__address) THREAD->kstack); |
287 | if (THREAD->ustack) { |
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288 | frame_free((__address) THREAD->ustack); |
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1 | jermar | 289 | } |
290 | |||
291 | /* |
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292 | * Detach from the containing task. |
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293 | */ |
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15 | jermar | 294 | spinlock_lock(&TASK->lock); |
295 | list_remove(&THREAD->th_link); |
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296 | spinlock_unlock(&TASK->lock); |
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1 | jermar | 297 | |
15 | jermar | 298 | spinlock_unlock(&THREAD->lock); |
1 | jermar | 299 | |
300 | spinlock_lock(&threads_lock); |
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15 | jermar | 301 | list_remove(&THREAD->threads_link); |
1 | jermar | 302 | spinlock_unlock(&threads_lock); |
73 | vana | 303 | |
99 | jermar | 304 | spinlock_lock(&CPU->lock); |
305 | if(CPU->fpu_owner==THREAD) CPU->fpu_owner=NULL; |
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306 | spinlock_unlock(&CPU->lock); |
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73 | vana | 307 | |
1 | jermar | 308 | |
15 | jermar | 309 | free(THREAD); |
1 | jermar | 310 | |
311 | break; |
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312 | |||
313 | case Sleeping: |
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314 | /* |
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315 | * Prefer the thread after it's woken up. |
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316 | */ |
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15 | jermar | 317 | THREAD->pri = -1; |
1 | jermar | 318 | |
319 | /* |
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320 | * We need to release wq->lock which we locked in waitq_sleep(). |
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15 | jermar | 321 | * Address of wq->lock is kept in THREAD->sleep_queue. |
1 | jermar | 322 | */ |
15 | jermar | 323 | spinlock_unlock(&THREAD->sleep_queue->lock); |
1 | jermar | 324 | |
325 | /* |
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326 | * Check for possible requests for out-of-context invocation. |
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327 | */ |
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15 | jermar | 328 | if (THREAD->call_me) { |
329 | THREAD->call_me(THREAD->call_me_with); |
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330 | THREAD->call_me = NULL; |
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331 | THREAD->call_me_with = NULL; |
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1 | jermar | 332 | } |
333 | |||
15 | jermar | 334 | spinlock_unlock(&THREAD->lock); |
1 | jermar | 335 | |
336 | break; |
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337 | |||
338 | default: |
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339 | /* |
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340 | * Entering state is unexpected. |
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341 | */ |
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15 | jermar | 342 | panic("tid%d: unexpected state %s\n", THREAD->tid, thread_states[THREAD->state]); |
1 | jermar | 343 | break; |
344 | } |
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15 | jermar | 345 | THREAD = NULL; |
1 | jermar | 346 | } |
347 | |||
15 | jermar | 348 | THREAD = find_best_thread(); |
1 | jermar | 349 | |
15 | jermar | 350 | spinlock_lock(&THREAD->lock); |
351 | priority = THREAD->pri; |
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352 | spinlock_unlock(&THREAD->lock); |
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1 | jermar | 353 | |
354 | relink_rq(priority); |
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355 | |||
15 | jermar | 356 | spinlock_lock(&THREAD->lock); |
1 | jermar | 357 | |
358 | /* |
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359 | * If both the old and the new task are the same, lots of work is avoided. |
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360 | */ |
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15 | jermar | 361 | if (TASK != THREAD->task) { |
1 | jermar | 362 | vm_t *m1 = NULL; |
363 | vm_t *m2; |
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364 | |||
15 | jermar | 365 | if (TASK) { |
366 | spinlock_lock(&TASK->lock); |
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367 | m1 = TASK->vm; |
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368 | spinlock_unlock(&TASK->lock); |
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1 | jermar | 369 | } |
370 | |||
15 | jermar | 371 | spinlock_lock(&THREAD->task->lock); |
372 | m2 = THREAD->task->vm; |
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373 | spinlock_unlock(&THREAD->task->lock); |
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1 | jermar | 374 | |
375 | /* |
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376 | * Note that it is possible for two tasks to share one vm mapping. |
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377 | */ |
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378 | if (m1 != m2) { |
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379 | /* |
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380 | * Both tasks and vm mappings are different. |
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381 | * Replace the old one with the new one. |
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382 | */ |
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383 | if (m1) { |
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384 | vm_uninstall(m1); |
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385 | } |
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386 | vm_install(m2); |
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387 | } |
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15 | jermar | 388 | TASK = THREAD->task; |
1 | jermar | 389 | } |
390 | |||
15 | jermar | 391 | THREAD->state = Running; |
1 | jermar | 392 | |
393 | #ifdef SCHEDULER_VERBOSE |
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15 | jermar | 394 | printf("cpu%d: tid %d (pri=%d,ticks=%d,nrdy=%d)\n", CPU->id, THREAD->tid, THREAD->pri, THREAD->ticks, CPU->nrdy); |
1 | jermar | 395 | #endif |
396 | |||
15 | jermar | 397 | context_restore(&THREAD->saved_context); |
1 | jermar | 398 | /* not reached */ |
399 | } |
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400 | |||
107 | decky | 401 | |
1 | jermar | 402 | #ifdef __SMP__ |
107 | decky | 403 | /** Load balancing thread |
404 | * |
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405 | * SMP load balancing thread, supervising thread supplies |
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406 | * for the CPU it's wired to. |
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407 | * |
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408 | * @param arg Generic thread argument (unused). |
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409 | * |
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1 | jermar | 410 | */ |
411 | void kcpulb(void *arg) |
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412 | { |
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413 | thread_t *t; |
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414 | int count, i, j, k = 0; |
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415 | pri_t pri; |
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416 | |||
417 | loop: |
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418 | /* |
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419 | * Sleep until there's some work to do. |
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420 | */ |
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15 | jermar | 421 | waitq_sleep(&CPU->kcpulb_wq); |
1 | jermar | 422 | |
423 | not_satisfied: |
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424 | /* |
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425 | * Calculate the number of threads that will be migrated/stolen from |
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426 | * other CPU's. Note that situation can have changed between two |
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427 | * passes. Each time get the most up to date counts. |
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428 | */ |
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429 | pri = cpu_priority_high(); |
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15 | jermar | 430 | spinlock_lock(&CPU->lock); |
1 | jermar | 431 | count = nrdy / config.cpu_active; |
15 | jermar | 432 | count -= CPU->nrdy; |
433 | spinlock_unlock(&CPU->lock); |
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1 | jermar | 434 | cpu_priority_restore(pri); |
435 | |||
436 | if (count <= 0) |
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437 | goto satisfied; |
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438 | |||
439 | /* |
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440 | * Searching least priority queues on all CPU's first and most priority queues on all CPU's last. |
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441 | */ |
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442 | for (j=RQ_COUNT-1; j >= 0; j--) { |
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443 | for (i=0; i < config.cpu_active; i++) { |
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444 | link_t *l; |
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445 | runq_t *r; |
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446 | cpu_t *cpu; |
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447 | |||
448 | cpu = &cpus[(i + k) % config.cpu_active]; |
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449 | r = &cpu->rq[j]; |
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450 | |||
451 | /* |
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452 | * Not interested in ourselves. |
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453 | * Doesn't require interrupt disabling for kcpulb is X_WIRED. |
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454 | */ |
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15 | jermar | 455 | if (CPU == cpu) |
1 | jermar | 456 | continue; |
457 | |||
458 | restart: pri = cpu_priority_high(); |
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459 | spinlock_lock(&r->lock); |
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460 | if (r->n == 0) { |
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461 | spinlock_unlock(&r->lock); |
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462 | cpu_priority_restore(pri); |
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463 | continue; |
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464 | } |
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465 | |||
466 | t = NULL; |
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467 | l = r->rq_head.prev; /* search rq from the back */ |
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468 | while (l != &r->rq_head) { |
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469 | t = list_get_instance(l, thread_t, rq_link); |
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470 | /* |
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471 | * We don't want to steal CPU-wired threads neither threads already stolen. |
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472 | * The latter prevents threads from migrating between CPU's without ever being run. |
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73 | vana | 473 | * We don't want to steal threads whose FPU context is still in CPU |
474 | */ |
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1 | jermar | 475 | spinlock_lock(&t->lock); |
73 | vana | 476 | if ( (!(t->flags & (X_WIRED | X_STOLEN))) && (!(t->fpu_context_engaged)) ) { |
1 | jermar | 477 | /* |
478 | * Remove t from r. |
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479 | */ |
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480 | |||
481 | spinlock_unlock(&t->lock); |
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482 | |||
483 | /* |
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484 | * Here we have to avoid deadlock with relink_rq(), |
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485 | * because it locks cpu and r in a different order than we do. |
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486 | */ |
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487 | if (!spinlock_trylock(&cpu->lock)) { |
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488 | /* Release all locks and try again. */ |
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489 | spinlock_unlock(&r->lock); |
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490 | cpu_priority_restore(pri); |
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491 | goto restart; |
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492 | } |
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493 | cpu->nrdy--; |
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494 | spinlock_unlock(&cpu->lock); |
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495 | |||
111 | palkovsky | 496 | atomic_dec(&nrdy); |
1 | jermar | 497 | |
498 | r->n--; |
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499 | list_remove(&t->rq_link); |
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500 | |||
501 | break; |
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502 | } |
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503 | spinlock_unlock(&t->lock); |
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504 | l = l->prev; |
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505 | t = NULL; |
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506 | } |
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507 | spinlock_unlock(&r->lock); |
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508 | |||
509 | if (t) { |
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510 | /* |
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511 | * Ready t on local CPU |
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512 | */ |
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513 | spinlock_lock(&t->lock); |
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514 | #ifdef KCPULB_VERBOSE |
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15 | jermar | 515 | 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 | 516 | #endif |
517 | t->flags |= X_STOLEN; |
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518 | spinlock_unlock(&t->lock); |
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519 | |||
520 | thread_ready(t); |
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521 | |||
522 | cpu_priority_restore(pri); |
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523 | |||
524 | if (--count == 0) |
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525 | goto satisfied; |
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526 | |||
527 | /* |
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528 | * We are not satisfied yet, focus on another CPU next time. |
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529 | */ |
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530 | k++; |
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531 | |||
532 | continue; |
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533 | } |
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534 | cpu_priority_restore(pri); |
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535 | } |
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536 | } |
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537 | |||
15 | jermar | 538 | if (CPU->nrdy) { |
1 | jermar | 539 | /* |
540 | * Be a little bit light-weight and let migrated threads run. |
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541 | */ |
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542 | scheduler(); |
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543 | } |
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544 | else { |
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545 | /* |
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546 | * We failed to migrate a single thread. |
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547 | * Something more sophisticated should be done. |
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548 | */ |
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549 | scheduler(); |
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550 | } |
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551 | |||
552 | goto not_satisfied; |
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553 | |||
554 | satisfied: |
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555 | /* |
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556 | * Tell find_best_thread() to wake us up later again. |
||
557 | */ |
||
15 | jermar | 558 | CPU->kcpulbstarted = 0; |
1 | jermar | 559 | goto loop; |
560 | } |
||
561 | |||
562 | #endif /* __SMP__ */ |