wait_event_interruptible(wq, condition)

wait_event_interruptible()。该函数修改task的状态为TASK_INTERRUPTIBLE，意味着改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，如果是则直接返回0，否则调用__wait_event_interruptible()，并用__ret来存放返回值
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#define wait_event_interruptible(wq, condition)          \
({                                                       \
    int __ret = 0;                                       \
    if (!(condition))                                    \
        __wait_event_interruptible(wq, condition, __ret);\
    __ret;                                               \
})