1 #include <common/semaphore.h>
2 #include <sched/sched.h>
3 #include <process/process.h>
4 
5 
semaphore_down(semaphore_t * sema)6 void semaphore_down(semaphore_t *sema)
7 {
8     if (atomic_read(&sema->counter) > 0) // 信号量大于0，资源充足
9         atomic_dec(&sema->counter);
10     else // 资源不足，进程休眠
11     {
12         // 将当前进程加入信号量的等待队列
13         wait_queue_node_t wait;
14         wait_queue_init(&wait, current_pcb);
15 
16         current_pcb->state = PROC_UNINTERRUPTIBLE;
17 
18         list_append(&sema->wait_queue.wait_list, &wait.wait_list);
19 
20         // 执行调度
21         current_pcb->flags |= PF_NEED_SCHED;
22         sched();
23     }
24 }
25 
semaphore_up(semaphore_t * sema)26 void semaphore_up(semaphore_t *sema)
27 {
28     if (list_empty(&sema->wait_queue.wait_list)) // 没有进程在等待资源
29     {
30         atomic_inc(&sema->counter);
31     }
32     else    // 有进程在等待资源，唤醒进程
33     {
34 
35         wait_queue_node_t *wq = container_of(list_next(&sema->wait_queue.wait_list), wait_queue_node_t, wait_list);
36         list_del(&wq->wait_list);
37 
38         process_wakeup_immediately(wq->pcb);
39     }
40 };