Linux Device Drivers Development

Predefined (shared) workqueue and standard workqueue functions

The predefined work queue is defined in kernel/workqueue.c as follows:

struct workqueue_struct *system_wq __read_mostly; 

This is just standard work for which the kernel provides a custom API that simply wraps around the standard one.

Comparisons between kernel predefined work queue functions and standard work queue functions are shown as follows:

Predefined work queue function	Equivalent standard work queue function
schedule_work(w)	queue_work(keventd_wq,w)
schedule_delayed_work(w,d)	queue_delayed_work(keventd_wq,w,d)(on any CPU)
schedule_delayed_work_on(cpu,w,d)	queue_delayed_work(keventd_wq,w,d) (on a given CPU)
flush_scheduled_work()	flush_workqueue(keventd_wq) ...