// 而它在调度器调度运行时已经从队列上取下了
// 运行时不在任何队列上，所以只需要直接调整
+ int old_priority = current->priority;
+
current->priority = priority;
// irq_restore(eflags);
// 降低优先级应该触发调度
- // 这里简单实现，更复杂的实现，应该是看有没有比priority更高的任务在就绪队列上再决定要不要重新调度
- if (current->priority < priority) {
+ if ((old_priority < priority) && priority_readyq_has_higher_priority_task(priority)) {
set_need_schedule();
}
}
+static void _priority_readyq_enqueue(task_t* task, bool at_head) {
+ assert(task != NULL);
+
+ int priority = task->priority;
+
+ assert(priority >= TASK_PRIORITY_MIN);
+ assert(priority <= TASK_PRIORITY_MAX);
+
+ if (at_head) {
+ list_add(&task->ready_list, g_priority_readyq.lists + priority);
+ } else {
+ list_add_tail(&task->ready_list, g_priority_readyq.lists + priority);
+ }
+
+ priority_readyq_set_bit(priority);
+}
+
+void priority_readyq_enqueue_head(task_t* task) {
+ _priority_readyq_enqueue(task, true);
+}
+
+void priority_readyq_enqueue_tail(task_t* task) {
+ _priority_readyq_enqueue(task, false);
+}
+
+void priority_readyq_unlink(task_t* task) {
+ assert(task != NULL);
+
+ int priority = task->priority;
+
+ assert(priority >= TASK_PRIORITY_MIN);
+ assert(priority <= TASK_PRIORITY_MAX);
+
+ assert(!list_empty(&task->ready_list));
+
+ list_del_init(&task->ready_list);
+
+ if (list_empty(g_priority_readyq.lists + priority)) {
+ priority_readyq_clear_bit(priority);
+ }
+}
+
+bool priority_readyq_has_higher_priority_task(int priority) {
+ assert(priority >= TASK_PRIORITY_MIN);
+ assert(priority <= TASK_PRIORITY_MAX);
+
+ int end_index = priority / READYQ_BITS_PER_WORD;
+ int bit_index = priority % READYQ_BITS_PER_WORD;
+
+ for (int i = 0; i < end_index; i++) {
+ if (g_priority_readyq.bitmap[i] != 0) {
+ return true;
+ }
+ }
+
+ // 虽然bit_index为0的情况下这个if必不满足，但不影响逻辑正确性
+ if (g_priority_readyq.bitmap[end_index] & ((1U << bit_index) - 1)) {
+ return true;
+ }
+
+ return false;
+}
+
void setup_tasks() {
INIT_LIST_HEAD(&all_tasks);
// INIT_LIST_HEAD(&ready_tasks);
unsigned long eflags;
irq_save(eflags);
- // 把自己挂到就绪队列尾部
+ // prev->state == TASK_WAIT 的进程也可能走到这里来，因为这还是切换前
if (prev->state == TASK_READY || prev->state == TASK_RUN) {
- task_set_ready(prev);
+ prev->state = TASK_READY;
+ assert(list_empty(&prev->ready_list));
+ if (prev != &root_task) {
+ // 如果时间片没有耗尽(例如：被高优先级的进程抢占了，或者主动让出CPU)，还是把自己挂队列头部，下次还是该优先级第一个被调度，以消耗完全余下的时间片
+ // 如果时间片耗尽了，就把自己挂到就绪队列尾部，下次调度时会重新分配时间片
+ if (prev->ticks_left > 0) {
+ priority_readyq_enqueue_head(prev);
+ } else {
+ priority_readyq_enqueue_tail(prev);
+ }
+ }
}
next = pick_next_task();
next = &root_task;
next->ticks_left = 1;
} else {
- list_del_init(&next->ready_list);
+ priority_readyq_unlink(next);
next->state = TASK_RUN;
if (next->ticks_left <= 0) {
next->ticks_left = TASK_TICKS_PER_QUANTUM;
}
- if (list_empty(g_priority_readyq.lists + next->priority)) {
- priority_readyq_clear_bit(next->priority);
- }
}
-#if 0
- if (list_empty(&ready_tasks)) {
- next = &root_task;
- goto end;
- }
-
- // 从ready_tasks中选择第一个
- next = list_entry(ready_tasks.next, task_t, ready_list);
-
- assert(next->state == TASK_READY);
- assert(next != &root_task);
-
-end:
- task_set_run(next);
-#endif
-
clear_need_schedule();
if (prev != next) {
monitor_tasks[id] = tsk;
}
-// void task_set_run(task_t* t) {
-// assert(t != NULL);
-
-// // if (t == &root_task) {
-// // t->state = TASK_RUN;
-// // return;
-// // }
-
-// assert(t->state == TASK_READY);
-
-// unsigned long eflags;
-// irq_save(eflags);
-
-// list_del_init(&t->ready_list);
-// t->state = TASK_RUN;
-
-// irq_restore(eflags);
-// }
-
void task_set_ready(task_t* t) {
assert(t != NULL);
if (t == &root_task) {
unsigned long eflags;
irq_save(eflags);
- //
- if (!list_empty(&t->ready_list)) {
- list_del_init(&t->ready_list);
- }
+ // 不应该出现重复设置ready的情况
+ assert(list_empty(&t->ready_list));
//
- assert(t->priority >= TASK_PRIORITY_MIN);
- assert(t->priority <= TASK_PRIORITY_MAX);
- list_head_t* list = g_priority_readyq.lists + t->priority;
- list_add_tail(&t->ready_list, list);
- priority_readyq_set_bit(t->priority);
+ priority_readyq_enqueue_tail(t);
t->state = TASK_READY;
+ if (t->priority < current->priority || current == &root_task) {
+ set_need_schedule();
+ }
+
irq_restore(eflags);
}
-void task_set_wait(task_t* t) {
- assert(t != NULL);
- // printk("task_set_wait %s %d\n", t->name, t->state);
- assert(t != &root_task);
-
- unsigned long eflags;
- irq_save(eflags);
-
- list_del_init(&t->ready_list);
- t->state = TASK_WAIT;
+void task_set_wait() {
+ task_t* task = current;
+ assert(task != NULL);
+ assert(task != &root_task);
+ assert(task->state == TASK_RUN);
- irq_restore(eflags);
+ task->state = TASK_WAIT;
}
void task_init_lists(task_t* t) {