1.\" $NetBSD: _lwp_ctl.2,v 1.3 2009/02/17 18:51:56 njoly Exp $ 2.\" 3.\" Copyright (c)2007 YAMAMOTO Takashi, 4.\" All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 15.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 16.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 17.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 18.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 19.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 20.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 21.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 22.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 23.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 24.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 25.\" SUCH DAMAGE. 26.\" 27.\" ------------------------------------------------------------ 28.Dd May 5, 2008 29.Dt _LWP_CTL 2 30.Os 31.Sh NAME 32.Nm _lwp_ctl 33.Nd prepare per-LWP communication area between kernel and userland 34.\" ------------------------------------------------------------ 35.Sh LIBRARY 36.Lb libc 37.\" ------------------------------------------------------------ 38.Sh SYNOPSIS 39.In lwp.h 40.Ft int 41.Fn _lwp_ctl "int features" "struct lwpctl **address" 42.\" ------------------------------------------------------------ 43.Sh DESCRIPTION 44.Fn _lwp_ctl 45prepares per-LWP communication area for the calling LWP, 46and maps it into the calling process' address space. 47It takes the following arguments. 48.Bl -tag -width features 49.It Fa features 50The bitwise-OR of the following flags. 51.Bl -tag -width LWPCTL_FEATURE_CURCPU 52.It Dv LWPCTL_FEATURE_CURCPU 53Request lc_curcpu. 54.It Dv LWPCTL_FEATURE_PCTR 55Request lc_pctr. 56.El 57.It Fa address 58The address to store a pointer to lwpctl structure for the calling LWP. 59.El 60.Pp 61The per-LWP communication area is described by an lwpctl structure. 62It has following members, depending on 63.Fa features . 64.Bl -tag -width int_lc_curcpu 65.It int lc_curcpu 66The integral identifier of the CPU on which the LWP is running, 67or 68.Dv LWPCTL_CPU_NONE 69when the LWP is not running on any CPU. 70It's updated by the kernel and should be considered as read-only for 71userland. 72It's available only if requested with the 73.Dv LWPCTL_FEATURE_CURCPU 74flag. 75.It int lc_pctr 76The integer which is incremented on every context switches to the LWP. 77It can be used to detect preemption of the LWP. 78(thus its name "preemption counter".) 79It's updated by the kernel and should be considered as read-only for 80userland. 81It's available only if requested with the 82.Dv LWPCTL_FEATURE_PCTR 83flag. 84.El 85.\" ------------------------------------------------------------ 86.Sh RETURN VALUES 87.Fn _lwp_ctl 88returns 0 on success. 89Otherwise, \-1 is returned and 90.Va errno 91is set to indicate the error. 92.\" ------------------------------------------------------------ 93.\".Sh ERRORS 94.\" ------------------------------------------------------------ 95.Sh SEE ALSO 96.Xr errno 2 97