内核版本为:2.4.10
等待队列
相关结构体:
DECLARE_WAITQUEUE(wait, current); // 定义一个等待队列,和当前进程挂钩
#define DECLARE_WAITQUEUE(name, tsk) wait_queue_t name = __WAITQUEUE_INITIALIZER(name, tsk)
#define __WAITQUEUE_INITIALIZER(name, tsk) { \
task: tsk, \
task_list: { NULL, NULL }, \
// 等待队列
struct __wait_queue {
unsigned int flags;
#define WQ_FLAG_EXCLUSIVE 0x01
struct task_struct *task;
struct list_head task_list;
#if WAITQUEUE_DEBUG
long __magic;
long __waker;
#endif
};
typedef struct __wait_queue wait_queue_t;
// 等待队列头
struct __wait_queue_head {
wq_lock_t lock; // 读写锁
struct list_head task_list;
#if WAITQUEUE_DEBUG
long __magic;
long __creator;
#endif
};
typedef struct __wait_queue_head wait_queue_head_t;
// 信号量
struct semaphore {
atomic_t count;
int sleepers;
wait_queue_head_t wait;
#if WAITQUEUE_DEBUG
long __magic;
#endif
};
函数操作:
将等待队列挂入等待队列头
add_wait_queue_exclusive(&sem->wait, &wait); // void add_wait_queue_exclusive(wait_queue_head_t *q, wait_queue_t * wait)
wait->flags &= ~WQ_FLAG_EXCLUSIVE;
__add_wait_queue_tail(q, wait); // (&sem->wait, &wait) //
list_add_tail(&new->task_list, &head->task_list); // &wait->task_list挂入sem->wait->task_list尾部
将等待队列从队列头上卸载
remove_wait_queue(&sem->wait, &wait);
__remove_wait_queue(q, wait); // (&sem->wait, &wait)
list_del(&old->task_list); // wait->task_list
唤醒等待队列头
wake_up(&sem->wait); // 唤醒信号量上面的进程
链表相关的操作:
结构体
strut list_head {
struct list_head *next, *prev;
};
初始化
1 结构体方式
#define LIST_HEAD_INIT(name) {&(name), &(name)}
#define LIST_HEAD(name) struct list_head name = LIST_HEAD_INIT(name)
2 指针方式
#define INIT_LIST_HEAD(ptr) do { \
(ptr)->next = (ptr); (ptr)->prev = (ptr); \
} while (0)
向链表里面插入元素
void __list_add(struct list_head *new, struct list_head *prev, struct list_head *next)
{
prev->next = new;
new->prev = prev;
new->next = next;
next->prev = new;
}
// 把new插入head后面,插入表头
void list_add(struct list_head *new, sturct list_head *head)
{
__list_add(new, head, head->next);
}
// 把new插入head前面,插入表尾
void list_add_tail(struct list_head *new, struct list_head *head)
{
__list_add(new, head->prev, head);
}
// 从链表里删除元素
void __list_del(struct list_head *prev, struct list_head *next)
{
prev->next = next;
next->prev = prev;
}
void list_del(struct list_head *entry)
{
__list_del(entry->prev, entry->next); // 出队列
entry->prev = entry->next = NULL; // 重新初始化entry
}
// 删除元素并初始化
void list_del_init(struct list_head *entry)
{
__list_del(entry->prev, entry->next);
INIT_LIST_HEAD(entry);
}
// 判断链表队列是否为空
int list_empty(struct list_head *head)
{
return (head->next == head);
}
// 链表拼接
// 把list链表接到head后面,实现链表合并,------> 链表队列的合并以及堆栈的原理!
void list_splice(struct list_head *list, struct list_head *head)
{
struct list_head *first = list->next;
if (list != first)
{
struct list_head *last = list->prev;
struct list_head *at = head->next;
head->next = first;
first->prev = head;
last->next = at;
at->prev = last;
}
}
// 通过指针获取到宿主结构,基本思想为通过list_head插槽的地址减去对应在宿主结构的偏移量
#define list_entry(ptr, type, member) \
(type *)((char *)ptr - (unsigned long)(&(((type *)0)->member)))