minix/lib/libc/sys/_lwp_ctl.2
Lionel Sambuc f14fb60209 Libraries updates and cleanup
* Updating common/lib
 * Updating lib/csu
 * Updating lib/libc
 * Updating libexec/ld.elf_so
 * Corrected test on __minix in featuretest to actually follow the
   meaning of the comment.
 * Cleaned up _REENTRANT-related defintions.
 * Disabled -D_REENTRANT for libfetch
 * Removing some unneeded __NBSD_LIBC defines and tests

Change-Id: Ic1394baef74d11b9f86b312f5ff4bbc3cbf72ce2
2013-01-14 11:36:26 +01:00

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.\" $NetBSD: _lwp_ctl.2,v 1.5 2012/04/13 15:14:58 yamt Exp $
.\"
.\" Copyright (c)2007 YAMAMOTO Takashi,
.\" All rights reserved.
.\"
.\" 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 AUTHOR 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 AUTHOR 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 April 13, 2012
.Dt _LWP_CTL 2
.Os
.Sh NAME
.Nm _lwp_ctl
.Nd prepare per-LWP communication area between kernel and userland
.\" ------------------------------------------------------------
.Sh LIBRARY
.Lb libc
.\" ------------------------------------------------------------
.Sh SYNOPSIS
.In sys/lwpctl.h
.In lwp.h
.Ft int
.Fn _lwp_ctl "int features" "struct lwpctl **address"
.\" ------------------------------------------------------------
.Sh DESCRIPTION
.Fn _lwp_ctl
prepares per-LWP communication area for the calling LWP,
and maps it into the calling process' address space.
It takes the following arguments.
.Bl -tag -width features
.It Fa features
The bitwise-OR of the following flags.
.Bl -tag -width LWPCTL_FEATURE_CURCPU
.It Dv LWPCTL_FEATURE_CURCPU
Request
.Vt lc_curcpu .
.It Dv LWPCTL_FEATURE_PCTR
Request
.Vt lc_pctr .
.El
.It Fa address
The address to store a pointer to
.Vt lwpctl
structure for the calling LWP.
.El
.Pp
The per-LWP communication area is described by an
.Vt lwpctl
structure.
It has following members, depending on
.Fa features .
.Bl -tag -width int_lc_curcpu
.It Vt int lc_curcpu
The integral identifier of the CPU on which the LWP is running,
or
.Dv LWPCTL_CPU_NONE
when the LWP is not running on any CPU.
It's updated by the kernel and should be considered as read-only for
userland.
It's available only if requested with the
.Dv LWPCTL_FEATURE_CURCPU
flag.
.It Vt int lc_pctr
The integer which is incremented on every context switches to the LWP.
It can be used to detect preemption of the LWP.
(thus its name "preemption counter".)
It's updated by the kernel and should be considered as read-only for
userland.
It's available only if requested with the
.Dv LWPCTL_FEATURE_PCTR
flag.
.El
.\" ------------------------------------------------------------
.Sh RETURN VALUES
.Fn _lwp_ctl
returns 0 on success.
Otherwise, \-1 is returned and
.Va errno
is set to indicate the error.
.\" ------------------------------------------------------------
.\".Sh ERRORS
.\" ------------------------------------------------------------
.Sh SEE ALSO
.Xr errno 2