Introduction: __kthread_unpark and __kthread_parkme are a pair of functions used for synchronization between kernel threads, usually used together.
1. Function prototype
(1)__kthread_unpark function prototype
void __kthread_unpark(struct task_struct *k);
该函数的参数k是一个指向要唤醒的内核线程的task_struct结构体指针。调用__kthread_unpark函数会唤醒指定的内核线程，使其从挂起状态恢复执行
(2)__kthread_parkme function prototype
void __kthread_parkme(void);
__kthread_parkme函数没有参数，返回值为void。在调用这个函数时，当前内核线程会被挂起等待，直到被其他线程调用__kthread_unpark函数唤醒。
2. Function usage scenarios
(1) Waiting for the occurrence of an event: When a kernel thread needs to wait for the occurrence of an event, it can use the __kthread_parkme function to suspend itself and wait. For example, in a device driver, you can use the __kthread_unpark function to wake up a waiting kernel thread when the device completes an operation.
(2) Waiting for the release of resources: When a kernel thread needs to wait for the release of a key resource, it can use the __kthread_parkme function to suspend itself and wait. For example, in the file system, when a process needs to access a file, if the file is occupied by other processes, the __kthread_parkme function can be used to suspend the process and wait for the file to be released.
(3) Waiting for the completion of other threads: When a kernel thread needs to wait for the completion of other threads, it can use the __kthread_parkme function to suspend itself and wait. For example, in multi-threaded programming, when a thread needs to wait for the results of other threads, it can use the __kthread_parkme function to suspend itself and wait for the completion of other threads.
The __kthread_unpark and __kthread_parkme functions are only a mechanism for kernel thread synchronization and communication. There are other synchronization mechanisms, such as semaphores, mutex locks, condition variables, etc. When choosing a synchronization mechanism, you need to make a choice based on specific needs and scenarios.
3.demo