2008-05-05 09:04:06 +04:00
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.\" $NetBSD: _lwp_ctl.2,v 1.2 2008/05/05 05:04:06 yamt Exp $
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2007-12-15 00:52:17 +03:00
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.\"
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.\" Copyright (c)2007 YAMAMOTO Takashi,
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" ------------------------------------------------------------
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2008-05-05 09:04:06 +04:00
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.Dd May 5, 2008
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2007-12-15 00:52:17 +03:00
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.Dt _LWP_CTL 2
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.Os
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.Sh NAME
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.Nm _lwp_ctl
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.Nd prepare per-LWP communication area between kernel and userland
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.\" ------------------------------------------------------------
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.Sh LIBRARY
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.Lb libc
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.\" ------------------------------------------------------------
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.Sh SYNOPSIS
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.In lwp.h
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.Ft int
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.Fn _lwp_ctl "int features" "struct lwpctl **address"
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.\" ------------------------------------------------------------
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.Sh DESCRIPTION
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.Fn _lwp_ctl
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prepares per-LWP communication area for the calling LWP,
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and maps it into the calling process' address space.
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It takes the following arguments.
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.Bl -tag -width features
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.It Fa features
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The bitwise-OR of the following flags.
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.Bl -tag -width LWPCTL_FEATURE_CURCPU
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.It Dv LWPCTL_FEATURE_CURCPU
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Request lc_curcpu.
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.It Dv LWPCTL_FEATURE_PCTR
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Request lc_pctr.
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2007-12-15 00:52:17 +03:00
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.El
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.It Fa address
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The address to store a pointer to lwpctl structure for the calling LWP.
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.El
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.Pp
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The per-LWP communication area is described by an lwpctl structure.
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It has following members, depending on
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.Fa features .
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.Bl -tag -width int_lc_curcpu
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.It int lc_curcpu
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The integral identifier of the CPU on which the LWP is running,
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or
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.Dv LWPCTL_CPU_NONE
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when the LWP is not running on any CPU.
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It's updated by the kernel and should be considered as read-only for
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userland.
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It's available only if requested with the
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.Dv LWPCTL_FEATURE_CURCPU
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flag.
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.El
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.Bl -tag -width int_lc_curcpu
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.It int lc_pctr
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The integer which is incremented on every context switches to the LWP.
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It can be used to detect preemption of the LWP.
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(thus its name "preemption counter".)
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It's updated by the kernel and should be considered as read-only for
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userland.
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It's available only if requested with the
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.Dv LWPCTL_FEATURE_PCTR
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flag.
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2007-12-15 00:52:17 +03:00
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.\" ------------------------------------------------------------
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.Sh RETURN VALUES
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.Fn _lwp_ctl
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returns 0 on success.
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Otherwise, \-1 is returned and
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.Va errno
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is set to indicate the error.
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.\" ------------------------------------------------------------
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.\".Sh ERRORS
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.\" ------------------------------------------------------------
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.Sh SEE ALSO
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.Xr errno 2
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