1.\" $NetBSD: kthread.9,v 1.7 2002/03/08 23:03:23 kleink Exp $ 2.\" 3.\" Copyright (c) 2000 The NetBSD Foundation, Inc. 4.\" All rights reserved. 5.\" 6.\" This code is derived from software contributed to The NetBSD Foundation 7.\" by Gregory McGarry. 8.\" 9.\" Redistribution and use in source and binary forms, with or without 10.\" modification, are permitted provided that the following conditions 11.\" are met: 12.\" 1. Redistributions of source code must retain the above copyright 13.\" notice, this list of conditions and the following disclaimer. 14.\" 2. Redistributions in binary form must reproduce the above copyright 15.\" notice, this list of conditions and the following disclaimer in the 16.\" documentation and/or other materials provided with the distribution. 17.\" 3. All advertising materials mentioning features or use of this software 18.\" must display the following acknowledgement: 19.\" This product includes software developed by the NetBSD 20.\" Foundation, Inc. and its contributors. 21.\" 4. Neither the name of The NetBSD Foundation nor the names of its 22.\" contributors may be used to endorse or promote products derived 23.\" from this software without specific prior written permission. 24.\" 25.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 26.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 27.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 28.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 29.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 30.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 31.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 32.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 33.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 34.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 35.\" POSSIBILITY OF SUCH DAMAGE. 36.\" 37.Dd July 9, 2000 38.Dt KTHREAD 9 39.Os 40.Sh NAME 41.Nm kthread_create1 , 42.Nm kthread_exit , 43.Nm kthread_create 44.Nd kernel threads 45.Sh SYNOPSIS 46.Fd #include \*[Lt]sys/kthread.h\*[Gt] 47.Ft void 48.Fn kthread_create "void (*func)(void *)" "void *arg" 49.Ft void 50.Fn kthread_exit "int ecode" 51.Ft int 52.Fn kthread_create1 "void (*func)(void *)" "void *arg" "struct proc **newpp" \ 53"const char *fmt" "..." 54.Sh DESCRIPTION 55Kernel threads are light-weight processes which execute entirely 56within the kernel. Any process can request the creation of a new 57kernel thread. Kernel threads are not swapped out during memory 58congestion. The VM space and limits are shared with proc0 (usually swapper). 59.Sh FUNCTIONS 60.Bl -tag -width compact 61.It Fn kthread_create1 "func" "arg" "newpp" "fmt" "..." 62Fork a kernel thread. 63.Fa newpp 64is a pointer the the new proc structure for the kernel thread. 65The function 66.Fa func 67is called with arguments 68.Fa arg 69to commence execution. 70.Fa fmt 71is a string containing format information used to display the kernel 72thread name. 73.It Fn kthread_create "void (*func)(void)" "void *arg" 74Register function 75.Fa func 76to defer creation of the kernel thread. Deferral of kernel thread 77creation is required during system startup when kernel thread resources 78are not available. 79.It Fn kthread_exit "int ecode" 80Exit from a kernel thread. 81.El 82.Sh RETURN VALUES 83Upon successful completion, 84.Fn kthread_create1 85returns 0. Otherwise, the following error values are returned: 86.Bl -tag -width [EAGAIN] 87.It Bq Er EAGAIN 88The limit on the total number of system processes would be exceeded. 89.It Bq Er EAGAIN 90The limit 91.Dv RLIMIT_NPROC 92on the total number of processes under execution by this 93user id would be exceeded. 94.El 95.Sh CODE REFERENCES 96This section describes places within the 97.Nx 98source tree where actual code implementing or utilising the kthread 99framework can be found. All pathnames are relative to 100.Pa /usr/src . 101.Pp 102The kthread framework itself is implemented within the file 103.Pa sys/kern/kern_kthread.c . 104Data structures and function prototypes for the framework are located in 105.Pa sys/sys/kthread.h . 106.Sh SEE ALSO 107.Xr driver 9 , 108.Xr fork1 9 109.Sh HISTORY 110The kthread framework appeared in 111.Nx 1.4 . 112