现在的位置: 首页 > 技术文章 > 驱动开发 > 正文

关于函数wait_event_interruptible(wq, condition)

2015年03月10日 驱动开发 ⁄ 共 1520字 ⁄ 字号 暂无评论 ⁄ 阅读 114 次

wait_event_interruptible(wq, condition),该函数修改task的状态为TASK_INTERRUPTIBLE,意味着该进程将不会继续运行直到被唤醒,然后被添加到等待队列wq中。

 

在wait_event_interruptible()中首先判断condition是不是已经满足,如果条件满足则直接返回0,否则调用__wait_event_interruptible(),并用__ret来存放返回值


#define wait_event_interruptible(wq, condition)          \
({                                                       \
int __ret = 0;                                       \
if (!(condition))                                    \
__wait_event_interruptible(wq, condition, __ret);\
__ret;                                               \
})

在无限循环中,__wait_event_interruptible()将本进程置为可中断的挂起状态,反复检查condition是否成立,如果成立则退出,如果不成立则继续休眠;条件满足后,即把本进程运行状态置为运行态

,并将__wait从等待队列中清除掉,从而进程能够调度运行。如果进程当前有异步信号(POSIX的),则返回-ERESTARTSYS。


#define __wait_event_interruptible(wq, condition, ret)      \
do {                                                        \
DEFINE_WAIT(__wait);                                    \
for (;;) {                                              \
prepare_to_wait(&wq, &__wait, TASK_INTERRUPTIBLE);  \
if (condition)                                      \
break;                                          \
if (!signal_pending(current)) {                     \
schedule();                                     \
continue;                                       \
}                                                   \
ret = -ERESTARTSYS;                                 \
break;                                              \
}                                                       \
finish_wait(&wq, &__wait);                              \
} while (0)

给我留言

留言无头像?



×