1.\" $NetBSD: kthread.9,v 1.9 2002/10/14 13:43:25 wiz 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. 57Any process can request the creation of a new kernel thread. 58Kernel threads are not swapped out during memory congestion. 59The VM space and limits are shared with proc0 (usually swapper). 60.Sh FUNCTIONS 61.Bl -tag -width compact 62.It Fn kthread_create1 "void (*func)(void *)" "void *arg" "struct proc **newpp" "const char *fmt" "..." 63Fork a kernel thread. 64.Fa newpp 65is a pointer the the new proc structure for the kernel thread. 66The function 67.Fa func 68is called with arguments 69.Fa arg 70to commence execution. 71.Fa fmt 72is a string containing format information used to display the kernel 73thread name. 74.It Fn kthread_create "void (*func)(void *)" "void *arg" 75Register function 76.Fa func 77to defer creation of the kernel thread. 78Deferral of kernel thread creation is required during system startup 79when kernel thread resources are not available. 80.It Fn kthread_exit "int ecode" 81Exit from a kernel thread. 82.El 83.Sh RETURN VALUES 84Upon successful completion, 85.Fn kthread_create1 86returns 0. 87Otherwise, the following error values are returned: 88.Bl -tag -width [EAGAIN] 89.It Bq Er EAGAIN 90The limit on the total number of system processes would be exceeded. 91.It Bq Er EAGAIN 92The limit 93.Dv RLIMIT_NPROC 94on the total number of processes under execution by this 95user id would be exceeded. 96.El 97.Sh CODE REFERENCES 98This section describes places within the 99.Nx 100source tree where actual code implementing or utilising the kthread 101framework can be found. 102All pathnames are relative to 103.Pa /usr/src . 104.Pp 105The kthread framework itself is implemented within the file 106.Pa sys/kern/kern_kthread.c . 107Data structures and function prototypes for the framework are located in 108.Pa sys/sys/kthread.h . 109.Sh SEE ALSO 110.Xr driver 9 , 111.Xr fork1 9 112.Sh HISTORY 113The kthread framework appeared in 114.Nx 1.4 . 115