Mastering Linux Kernel Development

Completion locks

Completion locks are an efficient way to achieve code synchronization if you need one or multiple threads of execution to wait for completion of some event, such as waiting for another process to reach a point or state. Completion locks may be preferred over a semaphore for a couple of reasons: multiple threads of execution can wait for a completion, and using complete_all(), they can all be released at once. This is way better than a semaphore waking up to multiple threads. Secondly, semaphores can lead to race conditions if a waiting thread deallocates the synchronization object; this problem doesn’t exist when using completion.

Completion can be used by including <linux/completion.h> and by creating a variable of type ...