1.\" $NetBSD: kthread.9,v 1.14 2005/09/10 22:21:41 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 August 27, 2005 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.In sys/kthread.h 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). 60A kernel thread must call 61.Fn kthread_exit 62to end execution. 63.Sh FUNCTIONS 64.Bl -tag -width compact 65.It Fn kthread_create1 "void (*func)(void *)" "void *arg" "struct proc **newpp" "const char *fmt" "..." 66Fork a kernel thread. 67.Fa newpp 68is a pointer the new proc structure for the kernel thread. 69The function 70.Fa func 71is called with arguments 72.Fa arg 73to commence execution. 74.Fa fmt 75is a string containing format information used to display the kernel 76thread name. 77The function 78.Fa func 79must not return. 80If the kernel thread runs to completion, it must call 81.Fn kthread_exit 82to properly terminate itself. 83.It Fn kthread_create "void (*func)(void *)" "void *arg" 84Register function 85.Fa func 86to defer creation of the kernel thread. 87Deferral of kernel thread creation is required during system startup 88when kernel thread resources are not available. 89.It Fn kthread_exit "int ecode" 90Exit from a kernel thread. 91.El 92.Sh RETURN VALUES 93Upon successful completion, 94.Fn kthread_create1 95returns 0. 96Otherwise, the following error values are returned: 97.Bl -tag -width [EAGAIN] 98.It Bq Er EAGAIN 99The limit on the total number of system processes would be exceeded. 100.It Bq Er EAGAIN 101The limit 102.Dv RLIMIT_NPROC 103on the total number of processes under execution by this 104user id would be exceeded. 105.El 106.Sh CODE REFERENCES 107This section describes places within the 108.Nx 109source tree where actual code implementing or using the kthread 110framework can be found. 111All pathnames are relative to 112.Pa /usr/src . 113.Pp 114The kthread framework itself is implemented within the file 115.Pa sys/kern/kern_kthread.c . 116Data structures and function prototypes for the framework are located in 117.Pa sys/sys/kthread.h . 118.Sh SEE ALSO 119.Xr driver 9 , 120.Xr fork1 9 121.Sh HISTORY 122The kthread framework appeared in 123.Nx 1.4 . 124