进程PCB的双向循环链表

进程链表示意图（linux-2.6.38内核）

  内核中对应结构体。

struct task_struct {
   ...;
    struct list_head tasks;
   ...;
};

struct list_head {
    struct list_head *next,*prev;
};

----------------------------------------------------------------------------------------

编写内核模块遍历双向循环链表。（逆序的方式，pid从大到小）

#include<linux/module.h>
#include<linux/init.h>
#include<linux/sched.h>

MODULE_LICENSE("GPL");

#ifndef offsetof
#define offsetof(type, field)   ((long) &((type *)0)->field)
#endif   /* offsetof */

#ifndef container_of
#define container_of(ptr, type, member) ({                      \
        const typeof( ((type *)0)->member ) *__mptr = (ptr);    \
        (type *)( (char *)__mptr - offsetof(type,member) );})
#endif

static __init int process_init(void)
{
    struct task_struct *task = NULL,*task_ptr = NULL;
    struct list_head *p = NULL;
    printk("<0> the pid = %d\n",init_task.pid);//init_task(0号进程的PCB 常驻内存(内核数据区))
    task = &init_task;
    p = &(task->tasks);
    for (p = &(task->tasks);(p=(p->prev)) != &(task->tasks);) {
     task_ptr = container_of(p,struct task_struct,tasks);
     printk("%d------------------>%s\n",task_ptr->pid,task_ptr->comm);
    }

    return 0;
}


static __exit void process_exit(void)
{
    printk("<0> bye! \n");
}

module_init(process_init);
module_exit(process_exit);