Workqueue (Slideshow)#

Workqueue: Motivation#

  • Kernel thread ⟶ has a process ID, and is thus schedulable

  • ⟶ process context

  • Commonly used to defer (postpone) work from atomic context

  • Optional thread pool: one work queue per CPU

Creating/Destroying a Workqueue#

#include <linux/workqueue.h>

struct workqueue_struct* create_workqueue(const char* name);
void destroy_workqueue(struct workqueue_struct* wq);

What is Work?#

struct work_struct#
#include <linux/workqueue.h>

struct work_struct;
typedef void (*work_func_t)(struct work_struct *work);
INIT_WORK(struct work_struct* work, work_func_t);

  • Basically, a function pointer

  • Usually part of a larger structure

    • ⟶ container_of()-like dance

Submitting Work#

#include <linux/workqueue.h>

bool queue_work(struct workqueue_struct* wq, struct work_struct* work);

  • Returns false if work is already submitted (and doesn’t submit it again)

  • Returns true if work has been successfully submitted

What’s this?

  • Work cannot be submitted twice, with different parameters

  • Typically used to call a function on something which contains work (⟶ container_of())

  • Function has to decide itself