哈工大软件学院操作系统实验4——信号量的实现和应用

#include <errno.h> #include <linux/kernel.h> #include <asm/segment.h> #include <asm/system.h> #include <linux/sched.h> #include <unistd.h> /*#include <signal.h>*/ #define MAX 30 char names[MAX][MAX] = {'\0'}; sem_t arr[30]= {NULL}; void MakeNull(queue *q) { q->front = 0; q->rear = MAX - 1; } int add(int x) { int y; y = (x+1)%MAX; return y; } void EnQueue(struct task_struct *curr, queue *q) { if(add(add(q->rear))==q->front) printk("queue is full"); else { q->rear = add(q->rear); q->task[q->rear]=curr; } } void DeQueue(queue *q) { if(add(q->rear)==q->front) { printk("queue is empty"); } else q->front = add(q->front); } struct task_struct *Front( queue* q ) { if(add(q->rear)==q->front) return NULL; else return (q->task[q->front]); } int sys_sem_open(const char *name, unsigned int value) { char n; int i = 0; int tag; char MyName[MAX]; while ((n = get_fs_byte(&name [i])) != '\0') { MyName[i] = n; i++; } MyName[i] = '\0'; for (i = 0; i < MAX; i++) { tag = strcmp(MyName,names[i]); if (tag==0) return &arr[i]; } for (i = 0; i < MAX; i++) { if (arr[i].flag == 0) { strcpy(names[i],MyName); arr[i].flag = 1; arr[i].value = value; /*printk("%d",value);*/ MakeNull( &(arr[i].wait)); return &arr[i]; } } return NULL; } int sys_sem_wait(sem_t *sem) { int value; cli(); (sem->value) = (sem->value)-1; value = sem->value; if (value < 0) { EnQueue(current, &(sem->wait)); /*sleep();*/ current->state = TASK_UNINTERRUPTIBLE; schedule(); } sti(); return 0; } int sys_sem_post(sem_t *sem) { struct task_struct* tmp; int value; cli(); (sem->value) = (sem->value)+1; value = sem->value; /*printk("post %d\t",sem->value);*/ if (value <= 0) { tmp = Front(&(sem->wait)); /*wake(tmp);*/ if (tmp != NULL) (*tmp).state = TASK_RUNNING; DeQueue(&(sem->wait)); } sti(); return 0; } int sys_sem_unlink(const char *name) { char n; int i=0,j=0,k=0; char aName[MAX]; int tag; while ((n = get_fs_byte(name + i)) != '\0') { aName[i] = n; i++; } aName[i] = '\0'; for(j=0; j<MAX; j++) { tag = strcmp(names[i],aName); if (tag==0) { arr[i].flag = 0; arr[i].value = 0; for(k=0;k<MAX;k++) { names[i][k] = '\0'; } return 0; } } return -1; }