sleep_timeout
时间: 2023-06-24 21:57:05 浏览: 136
sleep_timeout是一个可以在Android系统中设置的参数,用于控制屏幕自动息屏的时间。这个参数的单位是毫秒,代表设备在没有用户操作的情况下进入休眠状态的时间。在Android设备的设置中,可以找到“显示”选项,里面包含了“休眠”选项,可以设置屏幕自动熄灭的时间,这个时间就是通过修改sleep_timeout参数来实现的。例如,设置sleep_timeout为60000,表示设备在1分钟内没有任何用户操作时,屏幕将会自动熄灭。
相关问题
schedule_timeout和sleep_on_timeout的区别
`schedule_timeout` 和 `sleep_on_timeout` 都是 Linux 内核中用于等待一段时间的函数,但是它们具有以下几点不同:
1. 函数原型不同
`schedule_timeout` 的函数原型为:
```c
unsigned long schedule_timeout(unsigned long timeout);
```
而 `sleep_on_timeout` 的函数原型为:
```c
int sleep_on_timeout(void *queue, long timeout);
```
2. 返回值不同
`schedule_timeout` 的返回值是剩余的等待时间,即实际等待时间可能小于指定的等待时间,因为在等待期间可能会被唤醒。
`sleep_on_timeout` 的返回值是等待的结果,如果等待超时则返回 0,否则返回一个非零值。
3. 使用场景不同
`schedule_timeout` 主要用于等待一段时间,等待的过程中可以检查某个条件是否满足,如果满足则立即返回,否则继续等待。这个函数通常用于等待定时器、等待 I/O 操作等。
`sleep_on_timeout` 主要用于等待某个事件的发生,等待的过程中会让出 CPU,从而避免忙等待。这个函数通常用于等待某个进程或者线程执行完毕,或者等待某个条件成立。需要注意的是,`sleep_on_timeout` 会将进程置为睡眠状态,直到被唤醒,因此需要确保不会出现死锁或者竞争条件等问题。
how to used wait_event_interruptible_timeout
`wait_event_interruptible_timeout` is a function in the Linux kernel that allows a process to sleep until a certain condition is met or a timeout expires. The function prototype is as follows:
```
unsigned long wait_event_interruptible_timeout(wait_queue_head_t *q, int condition, unsigned long timeout);
```
Here are the parameters:
- `wait_queue_head_t *q`: A pointer to the wait queue head associated with the condition that the process is waiting for.
- `int condition`: The condition that the process is waiting for. The condition is typically a boolean expression that becomes true when some event occurs.
- `unsigned long timeout`: The maximum time in jiffies that the process will wait for the condition to become true. If the condition is not met by the timeout, the function returns 0.
Here's an example of how to use `wait_event_interruptible_timeout`:
```
#include <linux/wait.h>
#include <linux/sched.h>
DECLARE_WAIT_QUEUE_HEAD(my_wait_queue);
int my_condition = 0;
void my_function(void) {
unsigned long timeout = msecs_to_jiffies(5000); // wait for up to 5 seconds
int ret;
while (!my_condition) {
ret = wait_event_interruptible_timeout(my_wait_queue, my_condition, timeout);
if (ret == -ERESTARTSYS) {
// interrupted by a signal, handle the signal here
} else if (ret == 0) {
// timeout expired, handle the timeout here
} else {
// condition became true, handle the event here
}
}
}
```
In this example, `my_function` waits for `my_condition` to become true by calling `wait_event_interruptible_timeout` with a timeout of 5 seconds. The function sleeps until either the condition becomes true, the timeout expires, or it is interrupted by a signal. The return value of `wait_event_interruptible_timeout` indicates whether the condition became true, the timeout expired, or the function was interrupted by a signal.