Linux内核中工作队列(work_queue)的操作

// 保存线程指针
cwq->thread = p;
return p;
}
static int worker_thread(void *__cwq)
{
struct cpu_workqueue_struct *cwq = __cwq;
// 声明一个等待队列
DECLARE_WAITQUEUE(wait, current);
// 参数初始化定义, 而该宏用在程式之中对工作结构赋值
#define INIT_WORK(_work, _func, _data) \
do { \
INIT_LIST_HEAD(&(_work)->entry); \
(_work)->pending = 0; \
/*
* The externally visible workqueue abstraction is an array of
* per-CPU workqueues:
*/
// 工作队列结构
struct workqueue_struct {
struct cpu_workqueue_struct *cpu_wq;
int cpu)
{
// 每个CPU的工作队列
struct cpu_workqueue_struct *cwq = per_cpu_ptr(wq->cpu_wq, cpu);
struct task_struct *p;
spin_lock_init(&cwq->lock);
{
...
keventd_wq = create_workqueue("events");
...
}
核心创建函数是__reate_workqueue:
struct workqueue_struct *__create_workqueue(const char *name,
int singlethread)
// 工作队列节点
struct workqueue_struct *wq;
// 进程指针
struct task_struct *thread;
int run_depth; /* Detect run_workqueue() recursion depth */
} ____cacheline_aligned;
// 下一个要插入节点的序号
long insert_sequence; /* Next to add */
// 工作机构链表节点
struct list_head worklist;
// 要进行处理的等待队列
wait_queue_head_t more_work;
// 处理完的等待队列
wait_queue_head_t work_done;
destroy = 1;
}
}
mutex_unlock(&workqueue_mutex);
/*
* Was there any error during startup? If yes then clean up:
*/
if (destroy) {
// 建立线程失败, 释放工作队列
3. 一些宏定义
/* include/linux/workqueue.h */
// 初始化工作队列
#define __WORK_INITIALIZER(n, f, d) { \
// 初始化list
.entry = { &(n).entry, &(n).entry }, \
// 为每个CPU分配单独的工作队列空间
wq->cpu_wq = alloc_percpu(struct cpu_workqueue_struct);
if (!wq->cpu_wq) {
kfree(wq);
return NULL;
}
wq->name = name;
mutex_lock(&workqueue_mutex);
// 回调函数
.func = (f), \
// 回调函数参数
.data = (d), \
// 初始化定时器
.timer = TIMER_INITIALIZER(NULL, 0, 0), \
}
// 声明工作队列并初始化
#define DECLARE_WORK(n, f, d) \
const char *name;
struct list_head list; /* Empty if single thread */
};
kernel/workqueue.c中定义了一个工作队列链表, 任何工作队列能够挂接到这个链表中:
static LIST_HEAD(workqueues);
destroy_workqueue(wq);
wq = NULL;
}
return wq;
}
EXPORT_SYMBOL_GPL(__create_workqueue);
// 创建工作队列线程
static struct task_struct *create_workqueue_thread(struct workqueue_struct *wq,
for_each_online_cpu(cpu) {
p = create_workqueue_thread(wq, cpu);
if (p) {
// 绑定CPU
kthread_bind(p, cpu);
// 唤醒线程
wake_up_process(p);
} else
* flush_scheduled_work() was called.
*/
// 这个结构是针对每个CPU的
struct cpu_workqueue_struct {
// 结构锁
spinlock_t lock;
// 下一个要执行的节点序号
long remove_sequence; /* Least-recently added (next to run) */
* until all currently-scheduled works are completed, but it doesn't
* want to be livelocked by new, incoming ones. So it waits until
* remove_sequence is >= the insert_sequence which pertained when
struct work_struct n = __WORK_INITIALIZER(n, f, d)
/*
* initialize a work-struct's func and data pointers:
*/
// 重新定义工作结构参数
#define PREPARE_WORK(_work, _func, _data) \
/*
* The per-CPU workqueue (if single thread, we always use the first
* possible cpu).
*
* The sequence counters are for flush_scheduled_work(). It wants to wait
init_waitqueue_head(&cwq->more_work);
// 初始化等待队列work_done, 该队列处理执行完的工作结构
init_waitqueue_head(&cwq->work_done);
// 建立内核线程work_thread
if (is_single_threaded(wq))
struct work_struct {
// 等待时间
unsigned long pending;
// 链表节点
struct list_head entry;
// workqueue回调函数
void (*func)(void *);
// 回调函数func的数据
void *data;
{
int cpu, destroy = 0;
struct workqueue_struct *wq;
struct task_struct *p;
// 分配工作队列结构空间
wq = kzalloc(sizeof(*wq), GFP_KERNEL);
if (!wq)
return NULL;
1. 前言
工作队列(workqueue)的Linux内核中的定义的用来处理不是很紧急事件的回调方式处理方法.
以下代码的linux内核版本为2.6.19.2, 源代码文档主要为kernel/workqueue.c.
2. 数据结构
/* include/linux/workqueue.h */
// 工作节点结构
PREPARE_WORK((_work), (_func), (_data)); \
init_timer(&(_work)->timer); \
} while (0)
4. 操作函数
4.1 创建工作队列
一般的创建函数是create_workqueue, 但这其实只是个宏: