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WORKQUEUE(9)               Kernel Developer's Manual              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)

NetBSD 10.99                   December 28, 2017                  NetBSD 10.99