WORKQUEUE(9)

NAME
workqueue - simple do-it-in-thread-context framework

SYNOPSIS
#include <sys/workqueue.h>
int
workqueue_create(struct workqueue **wqp, const char *name, void (*func)(struct work *, void *), void *arg, pri_t prio, int ipl, int flags);
void
workqueue_enqueue(struct workqueue *wq, struct work *wk, struct cpu_info *ci);
void
workqueue_wait(struct workqueue *wq, struct work *wk);
void
workqueue_destroy(struct workqueue *wq);

DESCRIPTION
The workqueue utility routines are provided to defer work which is needed to be processed in a thread context.

workqueue_create() creates a workqueue. It takes the following arguments:

wqp Specify where to store the created workqueue.

name
    The name of the workqueue.

func
    The function to be called for each work.

arg An argument to be passed as a second argument of func.

prio
    The priority level for the worker threads.

ipl The highest IPL at which this workqueue is used.

flags
    The value of 0 indicates a standard create operation, however the following flags may be bitwise ORed together:

    WQ_FPU
        Specifies that the kthread must be allowed to use any machine-dependent per-CPU floating-point units or SIMD vector units, as in kthread_fpu_enter(9) / kthread_fpu_exit(9), when it executes the worker function.

    WQ_MPSAFE
        Specifies that the workqueue is multiprocessor safe and does its own locking; otherwise the kernel lock will be held while processing work.

    WQ_PERCPU
        Specifies that the workqueue should have a separate queue for each CPU, thus the work could be enqueued on concrete CPUs.

workqueue_enqueue() enqueues the work wk into the workqueue wq.

If the WQ_PERCPU flag was set on workqueue creation, the ci argument may be used to specify the CPU on which the work should be enqueued. Also it may be NULL, then work will be enqueued on the current CPU. If WQ_PERCPU flag was not set, ci must be NULL.

The enqueued work will be processed in a thread context. A work must not be enqueued again until the callback is called by the workqueue framework.

workqueue_wait() waits for a specified work wk on the workqueue wq to finish. The caller must ensure that wk will not be enqueued to the workqueue again until after workqueue_wait() returns.

workqueue_destroy() destroys a workqueue and frees associated resources. The caller should ensure that the workqueue has no work enqueued beforehand.

RETURN VALUES
workqueue_create() returns 0 on success. Otherwise, it returns an errno(2).

CODE REFERENCES
The workqueue subsystem is implemented within the file sys/kern/subr_workqueue.c.

SEE ALSO
callout(9), condvar(9), kthread(9), softint(9)