NetBSD/share/man/man9/workqueue.9

.\"	$NetBSD: workqueue.9,v 1.8 2009/08/04 18:59:05 wiz Exp $
.\"
.\" Copyright (c)2005 YAMAMOTO Takashi,
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.\" ------------------------------------------------------------
.Dd August 3, 2009
.Dt WORKQUEUE 9
.Os
.\" ------------------------------------------------------------
.Sh NAME
.Nm workqueue
.Nd simple do-it-in-thread-context framework
.\" ------------------------------------------------------------
.Sh SYNOPSIS
.In sys/workqueue.h
.\" - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
.Ft int
.Fn workqueue_create \
"struct workqueue **wqp" "const char *name" \
"void (*func)(struct work *, void *)" "void *arg" \
"pri_t prio" "int ipl" "int flags"
.\" - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
.Ft void
.Fn workqueue_enqueue \
"struct workqueue *wq" "struct work *wk" "struct cpu_info *ci"
.\" - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
.Ft void
.Fn workqueue_destroy \
"struct workqueue *wq"
.\" ------------------------------------------------------------
.Sh DESCRIPTION
The
.Nm
utility routines are provided to defer work which is needed to be
processed in a thread context.
.Pp
.\" - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
.Fn workqueue_create
creates a workqueue.
It takes the following arguments:
.Bl -tag -width flags
.It Fa wqp
Specify where to store the created workqueue.
.It Fa name
The name of the workqueue.
.It Fa func
The function to be called for each
.Fa work .
.It Fa arg
An argument to be passed as a second argument of
.Fa func .
.It Fa prio
The process priority to be used when sleeping to wait requests.
.It Fa ipl
The highest IPL at which this workqueue is used.
.It Fa flags
The value of 0 indicates a standard create operation, however the following
flags may be bitwise ORed together:
.Bl -tag -width WQ_MPSAFE
.It Dv WQ_MPSAFE
Specifies that the workqueue is multiprocessor safe and does its own locking,
otherwise the kernel lock will be held while work will be processed.
.It Dv WQ_PERCPU
Specifies that the workqueue should have a separate queue for each CPU,
thus the work could be enqueued on concrete CPUs.
.El
.El
.Pp
.\" - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
.Fn workqueue_enqueue
enqueues the work
.Fa wk
into the workqueue
.Fa wq .
.Pp
If the
.Dv WQ_PERCPU
flag was set on workqueue creation, the
.Fa ci
argument may be used to specify the CPU on which the work should
be enqueued.
Also it may be
.Dv NULL ,
then work will be enqueued on the current CPU.
If
.Dv WQ_PERCPU
flag was not set,
.Fa ci
must be
.Dv NULL .
.Pp
The enqueued work will be processed in a thread context.
A work must not be enqueued again until the callback is called by
the
.Nm
framework.
.Pp
.\" - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
.Fn workqueue_destroy
destroys a workqueue and frees associated resources.
The caller should ensure that the workqueue has no work enqueued beforehand.
.\" ------------------------------------------------------------
.Sh RETURN VALUES
.Fn workqueue_create
returns 0 on success.
Otherwise, it returns an
.Xr errno 2 .
.\" ------------------------------------------------------------
.Sh CODE REFERENCES
This section describes places within the
.Nx
source tree where actual code implementing the
.Nm
subsystem
can be found.
All pathnames are relative to
.Pa /usr/src .
.Pp
The
.Nm
subsystem is implemented within the file
.Pa sys/kern/subr_workqueue.c .
.\" ------------------------------------------------------------
.Sh SEE ALSO
.Xr callout 9 ,
.Xr condvar 9 ,
.Xr kthread 9 ,
.Xr softint 9