Add a manual page for producer/consumer queues, pcq(9), that I derived
from some documentation written by Matt Thomas.
This commit is contained in:
dyoung
parent
03c533138a
commit
e3420c6750
|
|
@ -0,0 +1,146 @@
|
|||
.\" $NetBSD: pcq.9,v 1.1 2010/01/04 18:00:26 dyoung Exp $
|
||||
.\" $NetBSD: pcq.9,v 1.1 2010/01/04 18:00:26 dyoung Exp $
|
||||
.\"
|
||||
.\" Copyright (c) 2010 The NetBSD Foundation, Inc.
|
||||
.\" All rights reserved.
|
||||
.\"
|
||||
.\" This code is derived from software contributed to The NetBSD Foundation
|
||||
.\" by Matt Thomas.
|
||||
.\"
|
||||
.\" Redistribution and use in source and binary forms, with or without
|
||||
.\" modification, are permitted provided that the following conditions
|
||||
.\" are met:
|
||||
.\" 1. Redistributions of source code must retain the above copyright
|
||||
.\" notice, this list of conditions and the following disclaimer.
|
||||
.\" 2. Redistributions in binary form must reproduce the above copyright
|
||||
.\" notice, this list of conditions and the following disclaimer in the
|
||||
.\" documentation and/or other materials provided with the distribution.
|
||||
.\"
|
||||
.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
|
||||
.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
|
||||
.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
|
||||
.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
|
||||
.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
|
||||
.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
|
||||
.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
|
||||
.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
|
||||
.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
|
||||
.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
|
||||
.\" POSSIBILITY OF SUCH DAMAGE.
|
||||
.\"
|
||||
.Dd January 2, 2010
|
||||
.Dt PCQ 9
|
||||
.Os
|
||||
.Sh NAME
|
||||
.Nm PCQ ,
|
||||
.Nm pcq_put ,
|
||||
.Nm pcq_peek ,
|
||||
.Nm pcq_get ,
|
||||
.Nm pcq_maxitems ,
|
||||
.Nm pcq_create ,
|
||||
.Nm pcq_destroy
|
||||
.Nd Producer/consumer queue.
|
||||
.Sh SYNOPSIS
|
||||
.In sys/pcq.h
|
||||
.Ft pcq_t *
|
||||
.Fn pcq_create "size_t maxlen" "km_flags_t kmflags"
|
||||
.Ft void
|
||||
.Fn pcq_destroy "pcq_t *pcq"
|
||||
.Ft void *
|
||||
.Fn pcq_get "pcq_t *pcq"
|
||||
.Ft size_t
|
||||
.Fn pcq_maxitems "pcq_t *pcq"
|
||||
.Ft void *
|
||||
.Fn pcq_peek "pcq_t *pcq"
|
||||
.Ft bool
|
||||
.Fn pcq_put "pcq_t *pcq" "void *item"
|
||||
.Sh DESCRIPTION
|
||||
The machine-independent
|
||||
.Nm
|
||||
framework provides producer/consumer queues.
|
||||
A queue
|
||||
.Po
|
||||
.Vt pcq_t
|
||||
.Pc
|
||||
allows multiple writers
|
||||
.Pq producers
|
||||
but only a single reader
|
||||
.Pq consumer .
|
||||
Compare-and-store operations are used to allow lockless updates.
|
||||
The consumer is expected to be protected by a mutex that covers
|
||||
the structure that the
|
||||
.Vt pcq_t
|
||||
is embedded into
|
||||
.Po
|
||||
e.g., socket lock, ifnet hwlock
|
||||
.Pc .
|
||||
These queues operate in a first-in, first-out
|
||||
.Pq FIFO
|
||||
manner.
|
||||
The act of inserting or removing an item from a
|
||||
.Vt pcq_t
|
||||
does not modify the item in any way.
|
||||
.Nm
|
||||
does not prevent an item being inserted multiple times into a single
|
||||
.Vt pcq_t .
|
||||
.Sh FUNCTIONS
|
||||
.Bl -tag -width compact
|
||||
.It Fn pcq_create "maxlen" "kmflags"
|
||||
Create a queue that can store at most
|
||||
.Fa maxlen
|
||||
items at one time.
|
||||
.Fa kmflags
|
||||
should be either
|
||||
.Dv KM_SLEEP ,
|
||||
if
|
||||
.Fn pcq_create
|
||||
should sleep until resources are available, or
|
||||
.Dv KM_NOSLEEP
|
||||
if it should return
|
||||
.Dv NULL
|
||||
if resources are unavailable.
|
||||
See
|
||||
.Xr kmem 9 .
|
||||
.It Fn pcq_destroy "pcq"
|
||||
Free the resources held by
|
||||
.Fa pcq .
|
||||
.It Fn pcq_get "pcq"
|
||||
Remove the next item to be consumed from the queue and return
|
||||
it.
|
||||
If the queue is empty,
|
||||
return
|
||||
.Dv NULL .
|
||||
.It Fn pcq_maxitems "pcq"
|
||||
Return the maximum number of items that the queue can store at
|
||||
any one time.
|
||||
.It Fn pcq_peek "pcq"
|
||||
Return the next item to be consumed from the queue but do not remove
|
||||
it from the queue.
|
||||
If the queue is empty,
|
||||
return
|
||||
.Dv NULL .
|
||||
.It Fn pcq_put "pcq" "item"
|
||||
Place an item at the end of the queue.
|
||||
If there is no room in the queue for the item, return
|
||||
.Dv false ;
|
||||
otherwise, return
|
||||
.Dv true .
|
||||
The item must not have the value of
|
||||
.Dv NULL .
|
||||
.El
|
||||
.Sh FILES
|
||||
.Bl -tag -width sys/kern/subr_pcq.c
|
||||
.It Pa sys/kern/subr_pcq.c
|
||||
.Nm
|
||||
implementation.
|
||||
.El
|
||||
.\" .Sh EXAMPLES
|
||||
.\" .Sh SEE ALSO
|
||||
.\" Cross-references should be ordered by section (low to high), then in
|
||||
.\" alphabetical order.
|
||||
.\" .Sh HISTORY
|
||||
.Sh AUTHORS
|
||||
.An Matt Thomas Aq matt@NetBSD.org
|
||||
.\" .Sh CAVEATS
|
||||
.\" .Sh BUGS
|
||||
.\" .Sh SECURITY CONSIDERATIONS
|
||||
Loading…
Reference in New Issue