int down_interruptible(struct semaphore *sem)
如果得不到信号量,此时没有信号打断,那么进入睡眠。
主要用来进程间的互斥同步
你如果看函数的注释,也可以知道大概的
66/**
67 * down_interruptible - acquire the semaphore unless interrupted
68 * @sem: the semaphore to be acquired
69 *
70 * Attempts to acquire the semaphore. If no more tasks are allowed to
71 * acquire the semaphore, calling this function will put the task to sleep.
72 * If the sleep is interrupted by a signal, this function will return -EINTR.
73 * If the semaphore is successfully acquired, this function returns 0.
74 */
75int down_interruptible(struct semaphore *sem)