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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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44 | |||
45 | #ifdef __SMP__ |
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11 | jermar | 46 | #include <arch/smp/atomic.h> |
1 | jermar | 47 | #endif /* __SMP__ */ |
48 | |||
49 | /* |
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50 | * NOTE ON ATOMIC READS: |
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51 | * Some architectures cannot read __u32 atomically. |
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52 | * For that reason, all accesses to nrdy and the likes must be protected by spinlock. |
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53 | */ |
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54 | |||
55 | spinlock_t nrdylock; |
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56 | volatile int nrdy; |
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57 | |||
52 | vana | 58 | void before_thread_runs(void) |
59 | { |
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60 | before_thread_runs_arch(); |
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57 | vana | 61 | fpu_context_restore(&(THREAD->saved_fpu_context)); |
52 | vana | 62 | } |
63 | |||
64 | |||
1 | jermar | 65 | void scheduler_init(void) |
66 | { |
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67 | spinlock_initialize(&nrdylock); |
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68 | } |
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69 | |||
70 | /* cpu_priority_high()'d */ |
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71 | struct thread *find_best_thread(void) |
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72 | { |
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73 | thread_t *t; |
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74 | runq_t *r; |
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75 | int i, n; |
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76 | |||
77 | loop: |
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78 | cpu_priority_high(); |
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79 | |||
15 | jermar | 80 | spinlock_lock(&CPU->lock); |
81 | n = CPU->nrdy; |
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82 | spinlock_unlock(&CPU->lock); |
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1 | jermar | 83 | |
84 | cpu_priority_low(); |
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85 | |||
86 | if (n == 0) { |
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87 | #ifdef __SMP__ |
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88 | /* |
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89 | * If the load balancing thread is not running, wake it up and |
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90 | * set CPU-private flag that the kcpulb has been started. |
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91 | */ |
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15 | jermar | 92 | if (test_and_set(&CPU->kcpulbstarted) == 0) { |
93 | waitq_wakeup(&CPU->kcpulb_wq, 0); |
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1 | jermar | 94 | goto loop; |
95 | } |
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96 | #endif /* __SMP__ */ |
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97 | |||
98 | /* |
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99 | * For there was nothing to run, the CPU goes to sleep |
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100 | * until a hardware interrupt or an IPI comes. |
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101 | * This improves energy saving and hyperthreading. |
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102 | * On the other hand, several hardware interrupts can be ignored. |
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103 | */ |
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104 | cpu_sleep(); |
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105 | goto loop; |
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106 | } |
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107 | |||
108 | cpu_priority_high(); |
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109 | |||
110 | for (i = 0; i<RQ_COUNT; i++) { |
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15 | jermar | 111 | r = &CPU->rq[i]; |
1 | jermar | 112 | spinlock_lock(&r->lock); |
113 | if (r->n == 0) { |
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114 | /* |
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115 | * If this queue is empty, try a lower-priority queue. |
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116 | */ |
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117 | spinlock_unlock(&r->lock); |
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118 | continue; |
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119 | } |
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120 | |||
121 | spinlock_lock(&nrdylock); |
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122 | nrdy--; |
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123 | spinlock_unlock(&nrdylock); |
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124 | |||
15 | jermar | 125 | spinlock_lock(&CPU->lock); |
126 | CPU->nrdy--; |
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127 | spinlock_unlock(&CPU->lock); |
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1 | jermar | 128 | |
129 | r->n--; |
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130 | |||
131 | /* |
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132 | * Take the first thread from the queue. |
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133 | */ |
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134 | t = list_get_instance(r->rq_head.next, thread_t, rq_link); |
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135 | list_remove(&t->rq_link); |
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136 | |||
137 | spinlock_unlock(&r->lock); |
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138 | |||
139 | spinlock_lock(&t->lock); |
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15 | jermar | 140 | t->cpu = CPU; |
1 | jermar | 141 | |
142 | t->ticks = us2ticks((i+1)*10000); |
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143 | t->pri = i; /* eventually correct rq index */ |
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144 | |||
145 | /* |
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146 | * Clear the X_STOLEN flag so that t can be migrated when load balancing needs emerge. |
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147 | */ |
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148 | t->flags &= ~X_STOLEN; |
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149 | spinlock_unlock(&t->lock); |
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150 | |||
151 | return t; |
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152 | } |
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153 | goto loop; |
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154 | |||
155 | } |
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156 | |||
157 | /* |
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158 | * This function prevents low priority threads from starving in rq's. |
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159 | * When it decides to relink rq's, it reconnects respective pointers |
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160 | * so that in result threads with 'pri' greater or equal 'start' are |
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161 | * moved to a higher-priority queue. |
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162 | */ |
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163 | void relink_rq(int start) |
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164 | { |
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165 | link_t head; |
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166 | runq_t *r; |
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167 | int i, n; |
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168 | |||
169 | list_initialize(&head); |
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15 | jermar | 170 | spinlock_lock(&CPU->lock); |
171 | if (CPU->needs_relink > NEEDS_RELINK_MAX) { |
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1 | jermar | 172 | for (i = start; i<RQ_COUNT-1; i++) { |
173 | /* remember and empty rq[i + 1] */ |
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15 | jermar | 174 | r = &CPU->rq[i + 1]; |
1 | jermar | 175 | spinlock_lock(&r->lock); |
176 | list_concat(&head, &r->rq_head); |
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177 | n = r->n; |
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178 | r->n = 0; |
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179 | spinlock_unlock(&r->lock); |
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180 | |||
181 | /* append rq[i + 1] to rq[i] */ |
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15 | jermar | 182 | r = &CPU->rq[i]; |
1 | jermar | 183 | spinlock_lock(&r->lock); |
184 | list_concat(&r->rq_head, &head); |
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185 | r->n += n; |
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186 | spinlock_unlock(&r->lock); |
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187 | } |
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15 | jermar | 188 | CPU->needs_relink = 0; |
1 | jermar | 189 | } |
15 | jermar | 190 | spinlock_unlock(&CPU->lock); |
1 | jermar | 191 | |
192 | } |
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193 | |||
194 | /* |
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195 | * The scheduler. |
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196 | */ |
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197 | void scheduler(void) |
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198 | { |
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199 | volatile pri_t pri; |
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200 | |||
201 | pri = cpu_priority_high(); |
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202 | |||
203 | if (haltstate) |
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204 | halt(); |
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205 | |||
15 | jermar | 206 | if (THREAD) { |
207 | spinlock_lock(&THREAD->lock); |
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57 | vana | 208 | fpu_context_save(&(THREAD->saved_fpu_context)); |
15 | jermar | 209 | if (!context_save(&THREAD->saved_context)) { |
1 | jermar | 210 | /* |
211 | * This is the place where threads leave scheduler(); |
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212 | */ |
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22 | jermar | 213 | before_thread_runs(); |
15 | jermar | 214 | spinlock_unlock(&THREAD->lock); |
215 | cpu_priority_restore(THREAD->saved_context.pri); |
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1 | jermar | 216 | return; |
217 | } |
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15 | jermar | 218 | THREAD->saved_context.pri = pri; |
1 | jermar | 219 | } |
220 | |||
221 | /* |
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222 | * We may not keep the old stack. |
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223 | * Reason: If we kept the old stack and got blocked, for instance, in |
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224 | * find_best_thread(), the old thread could get rescheduled by another |
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225 | * CPU and overwrite the part of its own stack that was also used by |
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226 | * the scheduler on this CPU. |
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227 | * |
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228 | * Moreover, we have to bypass the compiler-generated POP sequence |
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229 | * which is fooled by SP being set to the very top of the stack. |
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230 | * Therefore the scheduler() function continues in |
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231 | * scheduler_separated_stack(). |
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232 | */ |
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15 | jermar | 233 | context_save(&CPU->saved_context); |
234 | CPU->saved_context.sp = (__address) &CPU->stack[CPU_STACK_SIZE-8]; |
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235 | CPU->saved_context.pc = (__address) scheduler_separated_stack; |
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236 | context_restore(&CPU->saved_context); |
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1 | jermar | 237 | /* not reached */ |
238 | } |
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239 | |||
240 | void scheduler_separated_stack(void) |
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241 | { |
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242 | int priority; |
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243 | |||
15 | jermar | 244 | if (THREAD) { |
245 | switch (THREAD->state) { |
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1 | jermar | 246 | case Running: |
15 | jermar | 247 | THREAD->state = Ready; |
248 | spinlock_unlock(&THREAD->lock); |
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249 | thread_ready(THREAD); |
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1 | jermar | 250 | break; |
251 | |||
252 | case Exiting: |
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15 | jermar | 253 | frame_free((__address) THREAD->kstack); |
254 | if (THREAD->ustack) { |
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255 | frame_free((__address) THREAD->ustack); |
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1 | jermar | 256 | } |
257 | |||
258 | /* |
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259 | * Detach from the containing task. |
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260 | */ |
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15 | jermar | 261 | spinlock_lock(&TASK->lock); |
262 | list_remove(&THREAD->th_link); |
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263 | spinlock_unlock(&TASK->lock); |
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1 | jermar | 264 | |
15 | jermar | 265 | spinlock_unlock(&THREAD->lock); |
1 | jermar | 266 | |
267 | spinlock_lock(&threads_lock); |
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15 | jermar | 268 | list_remove(&THREAD->threads_link); |
1 | jermar | 269 | spinlock_unlock(&threads_lock); |
270 | |||
15 | jermar | 271 | free(THREAD); |
1 | jermar | 272 | |
273 | break; |
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274 | |||
275 | case Sleeping: |
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276 | /* |
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277 | * Prefer the thread after it's woken up. |
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278 | */ |
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15 | jermar | 279 | THREAD->pri = -1; |
1 | jermar | 280 | |
281 | /* |
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282 | * We need to release wq->lock which we locked in waitq_sleep(). |
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15 | jermar | 283 | * Address of wq->lock is kept in THREAD->sleep_queue. |
1 | jermar | 284 | */ |
15 | jermar | 285 | spinlock_unlock(&THREAD->sleep_queue->lock); |
1 | jermar | 286 | |
287 | /* |
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288 | * Check for possible requests for out-of-context invocation. |
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289 | */ |
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15 | jermar | 290 | if (THREAD->call_me) { |
291 | THREAD->call_me(THREAD->call_me_with); |
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292 | THREAD->call_me = NULL; |
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293 | THREAD->call_me_with = NULL; |
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1 | jermar | 294 | } |
295 | |||
15 | jermar | 296 | spinlock_unlock(&THREAD->lock); |
1 | jermar | 297 | |
298 | break; |
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299 | |||
300 | default: |
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301 | /* |
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302 | * Entering state is unexpected. |
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303 | */ |
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15 | jermar | 304 | panic("tid%d: unexpected state %s\n", THREAD->tid, thread_states[THREAD->state]); |
1 | jermar | 305 | break; |
306 | } |
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15 | jermar | 307 | THREAD = NULL; |
1 | jermar | 308 | } |
309 | |||
15 | jermar | 310 | THREAD = find_best_thread(); |
1 | jermar | 311 | |
15 | jermar | 312 | spinlock_lock(&THREAD->lock); |
313 | priority = THREAD->pri; |
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314 | spinlock_unlock(&THREAD->lock); |
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1 | jermar | 315 | |
316 | relink_rq(priority); |
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317 | |||
15 | jermar | 318 | spinlock_lock(&THREAD->lock); |
1 | jermar | 319 | |
320 | /* |
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321 | * If both the old and the new task are the same, lots of work is avoided. |
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322 | */ |
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15 | jermar | 323 | if (TASK != THREAD->task) { |
1 | jermar | 324 | vm_t *m1 = NULL; |
325 | vm_t *m2; |
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326 | |||
15 | jermar | 327 | if (TASK) { |
328 | spinlock_lock(&TASK->lock); |
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329 | m1 = TASK->vm; |
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330 | spinlock_unlock(&TASK->lock); |
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1 | jermar | 331 | } |
332 | |||
15 | jermar | 333 | spinlock_lock(&THREAD->task->lock); |
334 | m2 = THREAD->task->vm; |
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335 | spinlock_unlock(&THREAD->task->lock); |
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1 | jermar | 336 | |
337 | /* |
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338 | * Note that it is possible for two tasks to share one vm mapping. |
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339 | */ |
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340 | if (m1 != m2) { |
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341 | /* |
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342 | * Both tasks and vm mappings are different. |
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343 | * Replace the old one with the new one. |
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344 | */ |
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345 | if (m1) { |
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346 | vm_uninstall(m1); |
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347 | } |
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348 | vm_install(m2); |
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349 | } |
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15 | jermar | 350 | TASK = THREAD->task; |
1 | jermar | 351 | } |
352 | |||
15 | jermar | 353 | THREAD->state = Running; |
1 | jermar | 354 | |
355 | #ifdef SCHEDULER_VERBOSE |
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15 | jermar | 356 | printf("cpu%d: tid %d (pri=%d,ticks=%d,nrdy=%d)\n", CPU->id, THREAD->tid, THREAD->pri, THREAD->ticks, CPU->nrdy); |
1 | jermar | 357 | #endif |
358 | |||
15 | jermar | 359 | context_restore(&THREAD->saved_context); |
1 | jermar | 360 | /* not reached */ |
361 | } |
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362 | |||
363 | #ifdef __SMP__ |
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364 | /* |
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365 | * This is the load balancing thread. |
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366 | * It supervises thread supplies for the CPU it's wired to. |
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367 | */ |
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368 | void kcpulb(void *arg) |
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369 | { |
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370 | thread_t *t; |
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371 | int count, i, j, k = 0; |
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372 | pri_t pri; |
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373 | |||
374 | loop: |
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375 | /* |
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376 | * Sleep until there's some work to do. |
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377 | */ |
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15 | jermar | 378 | waitq_sleep(&CPU->kcpulb_wq); |
1 | jermar | 379 | |
380 | not_satisfied: |
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381 | /* |
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382 | * Calculate the number of threads that will be migrated/stolen from |
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383 | * other CPU's. Note that situation can have changed between two |
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384 | * passes. Each time get the most up to date counts. |
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385 | */ |
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386 | pri = cpu_priority_high(); |
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15 | jermar | 387 | spinlock_lock(&CPU->lock); |
1 | jermar | 388 | count = nrdy / config.cpu_active; |
15 | jermar | 389 | count -= CPU->nrdy; |
390 | spinlock_unlock(&CPU->lock); |
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1 | jermar | 391 | cpu_priority_restore(pri); |
392 | |||
393 | if (count <= 0) |
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394 | goto satisfied; |
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395 | |||
396 | /* |
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397 | * Searching least priority queues on all CPU's first and most priority queues on all CPU's last. |
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398 | */ |
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399 | for (j=RQ_COUNT-1; j >= 0; j--) { |
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400 | for (i=0; i < config.cpu_active; i++) { |
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401 | link_t *l; |
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402 | runq_t *r; |
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403 | cpu_t *cpu; |
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404 | |||
405 | cpu = &cpus[(i + k) % config.cpu_active]; |
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406 | r = &cpu->rq[j]; |
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407 | |||
408 | /* |
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409 | * Not interested in ourselves. |
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410 | * Doesn't require interrupt disabling for kcpulb is X_WIRED. |
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411 | */ |
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15 | jermar | 412 | if (CPU == cpu) |
1 | jermar | 413 | continue; |
414 | |||
415 | restart: pri = cpu_priority_high(); |
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416 | spinlock_lock(&r->lock); |
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417 | if (r->n == 0) { |
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418 | spinlock_unlock(&r->lock); |
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419 | cpu_priority_restore(pri); |
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420 | continue; |
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421 | } |
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422 | |||
423 | t = NULL; |
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424 | l = r->rq_head.prev; /* search rq from the back */ |
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425 | while (l != &r->rq_head) { |
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426 | t = list_get_instance(l, thread_t, rq_link); |
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427 | /* |
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428 | * We don't want to steal CPU-wired threads neither threads already stolen. |
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429 | * The latter prevents threads from migrating between CPU's without ever being run. |
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430 | */ |
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431 | spinlock_lock(&t->lock); |
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432 | if (!(t->flags & (X_WIRED | X_STOLEN))) { |
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433 | /* |
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434 | * Remove t from r. |
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435 | */ |
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436 | |||
437 | spinlock_unlock(&t->lock); |
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438 | |||
439 | /* |
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440 | * Here we have to avoid deadlock with relink_rq(), |
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441 | * because it locks cpu and r in a different order than we do. |
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442 | */ |
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443 | if (!spinlock_trylock(&cpu->lock)) { |
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444 | /* Release all locks and try again. */ |
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445 | spinlock_unlock(&r->lock); |
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446 | cpu_priority_restore(pri); |
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447 | goto restart; |
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448 | } |
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449 | cpu->nrdy--; |
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450 | spinlock_unlock(&cpu->lock); |
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451 | |||
452 | spinlock_lock(&nrdylock); |
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453 | nrdy--; |
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454 | spinlock_unlock(&nrdylock); |
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455 | |||
456 | r->n--; |
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457 | list_remove(&t->rq_link); |
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458 | |||
459 | break; |
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460 | } |
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461 | spinlock_unlock(&t->lock); |
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462 | l = l->prev; |
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463 | t = NULL; |
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464 | } |
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465 | spinlock_unlock(&r->lock); |
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466 | |||
467 | if (t) { |
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468 | /* |
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469 | * Ready t on local CPU |
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470 | */ |
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471 | spinlock_lock(&t->lock); |
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472 | #ifdef KCPULB_VERBOSE |
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15 | jermar | 473 | 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 | 474 | #endif |
475 | t->flags |= X_STOLEN; |
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476 | spinlock_unlock(&t->lock); |
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477 | |||
478 | thread_ready(t); |
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479 | |||
480 | cpu_priority_restore(pri); |
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481 | |||
482 | if (--count == 0) |
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483 | goto satisfied; |
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484 | |||
485 | /* |
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486 | * We are not satisfied yet, focus on another CPU next time. |
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487 | */ |
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488 | k++; |
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489 | |||
490 | continue; |
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491 | } |
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492 | cpu_priority_restore(pri); |
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493 | } |
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494 | } |
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495 | |||
15 | jermar | 496 | if (CPU->nrdy) { |
1 | jermar | 497 | /* |
498 | * Be a little bit light-weight and let migrated threads run. |
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499 | */ |
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500 | scheduler(); |
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501 | } |
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502 | else { |
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503 | /* |
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504 | * We failed to migrate a single thread. |
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505 | * Something more sophisticated should be done. |
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506 | */ |
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507 | scheduler(); |
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508 | } |
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509 | |||
510 | goto not_satisfied; |
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511 | |||
512 | satisfied: |
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513 | /* |
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514 | * Tell find_best_thread() to wake us up later again. |
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515 | */ |
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15 | jermar | 516 | CPU->kcpulbstarted = 0; |
1 | jermar | 517 | goto loop; |
518 | } |
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519 | |||
520 | #endif /* __SMP__ */ |