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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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40 | #include <typedefs.h> |
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41 | #include <mm/page.h> |
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42 | #include <synch/spinlock.h> |
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43 | |||
44 | #ifdef __SMP__ |
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11 | jermar | 45 | #include <arch/smp/atomic.h> |
1 | jermar | 46 | #endif /* __SMP__ */ |
47 | |||
48 | /* |
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49 | * NOTE ON ATOMIC READS: |
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50 | * Some architectures cannot read __u32 atomically. |
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51 | * For that reason, all accesses to nrdy and the likes must be protected by spinlock. |
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52 | */ |
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53 | |||
54 | spinlock_t nrdylock; |
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55 | volatile int nrdy; |
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56 | |||
57 | void scheduler_init(void) |
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58 | { |
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59 | spinlock_initialize(&nrdylock); |
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60 | } |
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61 | |||
62 | /* cpu_priority_high()'d */ |
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63 | struct thread *find_best_thread(void) |
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64 | { |
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65 | thread_t *t; |
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66 | runq_t *r; |
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67 | int i, n; |
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68 | |||
69 | loop: |
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70 | cpu_priority_high(); |
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71 | |||
15 | jermar | 72 | spinlock_lock(&CPU->lock); |
73 | n = CPU->nrdy; |
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74 | spinlock_unlock(&CPU->lock); |
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1 | jermar | 75 | |
76 | cpu_priority_low(); |
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77 | |||
78 | if (n == 0) { |
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79 | #ifdef __SMP__ |
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80 | /* |
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81 | * If the load balancing thread is not running, wake it up and |
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82 | * set CPU-private flag that the kcpulb has been started. |
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83 | */ |
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15 | jermar | 84 | if (test_and_set(&CPU->kcpulbstarted) == 0) { |
85 | waitq_wakeup(&CPU->kcpulb_wq, 0); |
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1 | jermar | 86 | goto loop; |
87 | } |
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88 | #endif /* __SMP__ */ |
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89 | |||
90 | /* |
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91 | * For there was nothing to run, the CPU goes to sleep |
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92 | * until a hardware interrupt or an IPI comes. |
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93 | * This improves energy saving and hyperthreading. |
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94 | * On the other hand, several hardware interrupts can be ignored. |
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95 | */ |
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96 | cpu_sleep(); |
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97 | goto loop; |
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98 | } |
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99 | |||
100 | cpu_priority_high(); |
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101 | |||
102 | for (i = 0; i<RQ_COUNT; i++) { |
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15 | jermar | 103 | r = &CPU->rq[i]; |
1 | jermar | 104 | spinlock_lock(&r->lock); |
105 | if (r->n == 0) { |
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106 | /* |
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107 | * If this queue is empty, try a lower-priority queue. |
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108 | */ |
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109 | spinlock_unlock(&r->lock); |
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110 | continue; |
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111 | } |
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112 | |||
113 | spinlock_lock(&nrdylock); |
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114 | nrdy--; |
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115 | spinlock_unlock(&nrdylock); |
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116 | |||
15 | jermar | 117 | spinlock_lock(&CPU->lock); |
118 | CPU->nrdy--; |
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119 | spinlock_unlock(&CPU->lock); |
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1 | jermar | 120 | |
121 | r->n--; |
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122 | |||
123 | /* |
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124 | * Take the first thread from the queue. |
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125 | */ |
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126 | t = list_get_instance(r->rq_head.next, thread_t, rq_link); |
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127 | list_remove(&t->rq_link); |
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128 | |||
129 | spinlock_unlock(&r->lock); |
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130 | |||
131 | spinlock_lock(&t->lock); |
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15 | jermar | 132 | t->cpu = CPU; |
1 | jermar | 133 | |
134 | t->ticks = us2ticks((i+1)*10000); |
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135 | t->pri = i; /* eventually correct rq index */ |
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136 | |||
137 | /* |
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138 | * Clear the X_STOLEN flag so that t can be migrated when load balancing needs emerge. |
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139 | */ |
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140 | t->flags &= ~X_STOLEN; |
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141 | spinlock_unlock(&t->lock); |
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142 | |||
143 | return t; |
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144 | } |
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145 | goto loop; |
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146 | |||
147 | } |
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148 | |||
149 | /* |
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150 | * This function prevents low priority threads from starving in rq's. |
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151 | * When it decides to relink rq's, it reconnects respective pointers |
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152 | * so that in result threads with 'pri' greater or equal 'start' are |
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153 | * moved to a higher-priority queue. |
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154 | */ |
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155 | void relink_rq(int start) |
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156 | { |
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157 | link_t head; |
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158 | runq_t *r; |
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159 | int i, n; |
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160 | |||
161 | list_initialize(&head); |
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15 | jermar | 162 | spinlock_lock(&CPU->lock); |
163 | if (CPU->needs_relink > NEEDS_RELINK_MAX) { |
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1 | jermar | 164 | for (i = start; i<RQ_COUNT-1; i++) { |
165 | /* remember and empty rq[i + 1] */ |
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15 | jermar | 166 | r = &CPU->rq[i + 1]; |
1 | jermar | 167 | spinlock_lock(&r->lock); |
168 | list_concat(&head, &r->rq_head); |
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169 | n = r->n; |
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170 | r->n = 0; |
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171 | spinlock_unlock(&r->lock); |
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172 | |||
173 | /* append rq[i + 1] to rq[i] */ |
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15 | jermar | 174 | r = &CPU->rq[i]; |
1 | jermar | 175 | spinlock_lock(&r->lock); |
176 | list_concat(&r->rq_head, &head); |
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177 | r->n += n; |
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178 | spinlock_unlock(&r->lock); |
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179 | } |
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15 | jermar | 180 | CPU->needs_relink = 0; |
1 | jermar | 181 | } |
15 | jermar | 182 | spinlock_unlock(&CPU->lock); |
1 | jermar | 183 | |
184 | } |
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185 | |||
186 | /* |
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187 | * The scheduler. |
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188 | */ |
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189 | void scheduler(void) |
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190 | { |
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191 | volatile pri_t pri; |
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192 | |||
193 | pri = cpu_priority_high(); |
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194 | |||
195 | if (haltstate) |
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196 | halt(); |
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197 | |||
15 | jermar | 198 | if (THREAD) { |
199 | spinlock_lock(&THREAD->lock); |
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200 | if (!context_save(&THREAD->saved_context)) { |
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1 | jermar | 201 | /* |
202 | * This is the place where threads leave scheduler(); |
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203 | */ |
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22 | jermar | 204 | before_thread_runs(); |
15 | jermar | 205 | spinlock_unlock(&THREAD->lock); |
206 | cpu_priority_restore(THREAD->saved_context.pri); |
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1 | jermar | 207 | return; |
208 | } |
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15 | jermar | 209 | THREAD->saved_context.pri = pri; |
1 | jermar | 210 | } |
211 | |||
212 | /* |
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213 | * We may not keep the old stack. |
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214 | * Reason: If we kept the old stack and got blocked, for instance, in |
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215 | * find_best_thread(), the old thread could get rescheduled by another |
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216 | * CPU and overwrite the part of its own stack that was also used by |
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217 | * the scheduler on this CPU. |
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218 | * |
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219 | * Moreover, we have to bypass the compiler-generated POP sequence |
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220 | * which is fooled by SP being set to the very top of the stack. |
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221 | * Therefore the scheduler() function continues in |
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222 | * scheduler_separated_stack(). |
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223 | */ |
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15 | jermar | 224 | context_save(&CPU->saved_context); |
225 | CPU->saved_context.sp = (__address) &CPU->stack[CPU_STACK_SIZE-8]; |
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226 | CPU->saved_context.pc = (__address) scheduler_separated_stack; |
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227 | context_restore(&CPU->saved_context); |
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1 | jermar | 228 | /* not reached */ |
229 | } |
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230 | |||
231 | void scheduler_separated_stack(void) |
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232 | { |
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233 | int priority; |
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234 | |||
15 | jermar | 235 | if (THREAD) { |
236 | switch (THREAD->state) { |
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1 | jermar | 237 | case Running: |
15 | jermar | 238 | THREAD->state = Ready; |
239 | spinlock_unlock(&THREAD->lock); |
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240 | thread_ready(THREAD); |
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1 | jermar | 241 | break; |
242 | |||
243 | case Exiting: |
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15 | jermar | 244 | frame_free((__address) THREAD->kstack); |
245 | if (THREAD->ustack) { |
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246 | frame_free((__address) THREAD->ustack); |
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1 | jermar | 247 | } |
248 | |||
249 | /* |
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250 | * Detach from the containing task. |
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251 | */ |
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15 | jermar | 252 | spinlock_lock(&TASK->lock); |
253 | list_remove(&THREAD->th_link); |
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254 | spinlock_unlock(&TASK->lock); |
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1 | jermar | 255 | |
15 | jermar | 256 | spinlock_unlock(&THREAD->lock); |
1 | jermar | 257 | |
258 | spinlock_lock(&threads_lock); |
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15 | jermar | 259 | list_remove(&THREAD->threads_link); |
1 | jermar | 260 | spinlock_unlock(&threads_lock); |
261 | |||
15 | jermar | 262 | free(THREAD); |
1 | jermar | 263 | |
264 | break; |
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265 | |||
266 | case Sleeping: |
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267 | /* |
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268 | * Prefer the thread after it's woken up. |
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269 | */ |
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15 | jermar | 270 | THREAD->pri = -1; |
1 | jermar | 271 | |
272 | /* |
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273 | * We need to release wq->lock which we locked in waitq_sleep(). |
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15 | jermar | 274 | * Address of wq->lock is kept in THREAD->sleep_queue. |
1 | jermar | 275 | */ |
15 | jermar | 276 | spinlock_unlock(&THREAD->sleep_queue->lock); |
1 | jermar | 277 | |
278 | /* |
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279 | * Check for possible requests for out-of-context invocation. |
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280 | */ |
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15 | jermar | 281 | if (THREAD->call_me) { |
282 | THREAD->call_me(THREAD->call_me_with); |
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283 | THREAD->call_me = NULL; |
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284 | THREAD->call_me_with = NULL; |
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1 | jermar | 285 | } |
286 | |||
15 | jermar | 287 | spinlock_unlock(&THREAD->lock); |
1 | jermar | 288 | |
289 | break; |
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290 | |||
291 | default: |
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292 | /* |
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293 | * Entering state is unexpected. |
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294 | */ |
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15 | jermar | 295 | panic("tid%d: unexpected state %s\n", THREAD->tid, thread_states[THREAD->state]); |
1 | jermar | 296 | break; |
297 | } |
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15 | jermar | 298 | THREAD = NULL; |
1 | jermar | 299 | } |
300 | |||
15 | jermar | 301 | THREAD = find_best_thread(); |
1 | jermar | 302 | |
15 | jermar | 303 | spinlock_lock(&THREAD->lock); |
304 | priority = THREAD->pri; |
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305 | spinlock_unlock(&THREAD->lock); |
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1 | jermar | 306 | |
307 | relink_rq(priority); |
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308 | |||
15 | jermar | 309 | spinlock_lock(&THREAD->lock); |
1 | jermar | 310 | |
311 | /* |
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312 | * If both the old and the new task are the same, lots of work is avoided. |
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313 | */ |
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15 | jermar | 314 | if (TASK != THREAD->task) { |
1 | jermar | 315 | vm_t *m1 = NULL; |
316 | vm_t *m2; |
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317 | |||
15 | jermar | 318 | if (TASK) { |
319 | spinlock_lock(&TASK->lock); |
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320 | m1 = TASK->vm; |
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321 | spinlock_unlock(&TASK->lock); |
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1 | jermar | 322 | } |
323 | |||
15 | jermar | 324 | spinlock_lock(&THREAD->task->lock); |
325 | m2 = THREAD->task->vm; |
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326 | spinlock_unlock(&THREAD->task->lock); |
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1 | jermar | 327 | |
328 | /* |
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329 | * Note that it is possible for two tasks to share one vm mapping. |
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330 | */ |
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331 | if (m1 != m2) { |
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332 | /* |
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333 | * Both tasks and vm mappings are different. |
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334 | * Replace the old one with the new one. |
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335 | */ |
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336 | if (m1) { |
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337 | vm_uninstall(m1); |
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338 | } |
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339 | vm_install(m2); |
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340 | } |
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15 | jermar | 341 | TASK = THREAD->task; |
1 | jermar | 342 | } |
343 | |||
15 | jermar | 344 | THREAD->state = Running; |
1 | jermar | 345 | |
346 | #ifdef SCHEDULER_VERBOSE |
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15 | jermar | 347 | printf("cpu%d: tid %d (pri=%d,ticks=%d,nrdy=%d)\n", CPU->id, THREAD->tid, THREAD->pri, THREAD->ticks, CPU->nrdy); |
1 | jermar | 348 | #endif |
349 | |||
15 | jermar | 350 | context_restore(&THREAD->saved_context); |
1 | jermar | 351 | /* not reached */ |
352 | } |
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353 | |||
354 | #ifdef __SMP__ |
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355 | /* |
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356 | * This is the load balancing thread. |
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357 | * It supervises thread supplies for the CPU it's wired to. |
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358 | */ |
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359 | void kcpulb(void *arg) |
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360 | { |
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361 | thread_t *t; |
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362 | int count, i, j, k = 0; |
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363 | pri_t pri; |
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364 | |||
365 | loop: |
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366 | /* |
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367 | * Sleep until there's some work to do. |
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368 | */ |
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15 | jermar | 369 | waitq_sleep(&CPU->kcpulb_wq); |
1 | jermar | 370 | |
371 | not_satisfied: |
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372 | /* |
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373 | * Calculate the number of threads that will be migrated/stolen from |
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374 | * other CPU's. Note that situation can have changed between two |
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375 | * passes. Each time get the most up to date counts. |
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376 | */ |
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377 | pri = cpu_priority_high(); |
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15 | jermar | 378 | spinlock_lock(&CPU->lock); |
1 | jermar | 379 | count = nrdy / config.cpu_active; |
15 | jermar | 380 | count -= CPU->nrdy; |
381 | spinlock_unlock(&CPU->lock); |
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1 | jermar | 382 | cpu_priority_restore(pri); |
383 | |||
384 | if (count <= 0) |
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385 | goto satisfied; |
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386 | |||
387 | /* |
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388 | * Searching least priority queues on all CPU's first and most priority queues on all CPU's last. |
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389 | */ |
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390 | for (j=RQ_COUNT-1; j >= 0; j--) { |
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391 | for (i=0; i < config.cpu_active; i++) { |
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392 | link_t *l; |
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393 | runq_t *r; |
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394 | cpu_t *cpu; |
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395 | |||
396 | cpu = &cpus[(i + k) % config.cpu_active]; |
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397 | r = &cpu->rq[j]; |
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398 | |||
399 | /* |
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400 | * Not interested in ourselves. |
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401 | * Doesn't require interrupt disabling for kcpulb is X_WIRED. |
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402 | */ |
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15 | jermar | 403 | if (CPU == cpu) |
1 | jermar | 404 | continue; |
405 | |||
406 | restart: pri = cpu_priority_high(); |
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407 | spinlock_lock(&r->lock); |
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408 | if (r->n == 0) { |
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409 | spinlock_unlock(&r->lock); |
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410 | cpu_priority_restore(pri); |
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411 | continue; |
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412 | } |
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413 | |||
414 | t = NULL; |
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415 | l = r->rq_head.prev; /* search rq from the back */ |
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416 | while (l != &r->rq_head) { |
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417 | t = list_get_instance(l, thread_t, rq_link); |
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418 | /* |
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419 | * We don't want to steal CPU-wired threads neither threads already stolen. |
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420 | * The latter prevents threads from migrating between CPU's without ever being run. |
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421 | */ |
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422 | spinlock_lock(&t->lock); |
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423 | if (!(t->flags & (X_WIRED | X_STOLEN))) { |
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424 | /* |
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425 | * Remove t from r. |
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426 | */ |
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427 | |||
428 | spinlock_unlock(&t->lock); |
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429 | |||
430 | /* |
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431 | * Here we have to avoid deadlock with relink_rq(), |
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432 | * because it locks cpu and r in a different order than we do. |
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433 | */ |
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434 | if (!spinlock_trylock(&cpu->lock)) { |
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435 | /* Release all locks and try again. */ |
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436 | spinlock_unlock(&r->lock); |
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437 | cpu_priority_restore(pri); |
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438 | goto restart; |
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439 | } |
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440 | cpu->nrdy--; |
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441 | spinlock_unlock(&cpu->lock); |
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442 | |||
443 | spinlock_lock(&nrdylock); |
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444 | nrdy--; |
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445 | spinlock_unlock(&nrdylock); |
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446 | |||
447 | r->n--; |
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448 | list_remove(&t->rq_link); |
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449 | |||
450 | break; |
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451 | } |
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452 | spinlock_unlock(&t->lock); |
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453 | l = l->prev; |
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454 | t = NULL; |
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455 | } |
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456 | spinlock_unlock(&r->lock); |
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457 | |||
458 | if (t) { |
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459 | /* |
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460 | * Ready t on local CPU |
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461 | */ |
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462 | spinlock_lock(&t->lock); |
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463 | #ifdef KCPULB_VERBOSE |
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15 | jermar | 464 | 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 | 465 | #endif |
466 | t->flags |= X_STOLEN; |
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467 | spinlock_unlock(&t->lock); |
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468 | |||
469 | thread_ready(t); |
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470 | |||
471 | cpu_priority_restore(pri); |
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472 | |||
473 | if (--count == 0) |
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474 | goto satisfied; |
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475 | |||
476 | /* |
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477 | * We are not satisfied yet, focus on another CPU next time. |
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478 | */ |
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479 | k++; |
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480 | |||
481 | continue; |
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482 | } |
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483 | cpu_priority_restore(pri); |
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484 | } |
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485 | } |
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486 | |||
15 | jermar | 487 | if (CPU->nrdy) { |
1 | jermar | 488 | /* |
489 | * Be a little bit light-weight and let migrated threads run. |
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490 | */ |
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491 | scheduler(); |
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492 | } |
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493 | else { |
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494 | /* |
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495 | * We failed to migrate a single thread. |
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496 | * Something more sophisticated should be done. |
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497 | */ |
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498 | scheduler(); |
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499 | } |
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500 | |||
501 | goto not_satisfied; |
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502 | |||
503 | satisfied: |
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504 | /* |
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505 | * Tell find_best_thread() to wake us up later again. |
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506 | */ |
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15 | jermar | 507 | CPU->kcpulbstarted = 0; |
1 | jermar | 508 | goto loop; |
509 | } |
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510 | |||
511 | #endif /* __SMP__ */ |