2007-01-20 16:24:44 +03:00
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.\" $NetBSD: _lwp_park.2,v 1.2 2007/01/20 13:24:44 wiz Exp $
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2007-01-20 04:41:00 +03:00
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.\"
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.\" Copyright (c) 2003, 2007 The NetBSD Foundation, Inc.
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.\" All rights reserved.
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.\"
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.\" This code is derived from software contributed to The NetBSD Foundation
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.\" by Jason R. Thorpe of Wasabi Systems, Inc, and by Andrew Doran.
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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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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the NetBSD
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.\" Foundation, Inc. and its contributors.
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.\" 4. Neither the name of The NetBSD Foundation nor the names of its
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.\" contributors may be used to endorse or promote products derived
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.\" from this software without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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.\" POSSIBILITY OF SUCH DAMAGE.
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.\"
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.Dd January 20, 2006
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.Dt _LWP_PARK 2
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.Os
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.Sh NAME
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.Nm _lwp_park
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.Nd wait interruptably in the kernel
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.Sh LIBRARY
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.Lb libc
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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_park "const struct timespec *abstime" "ucontext_t *uc" "const void *hint"
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.Sh DESCRIPTION
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.Fn _lwp_park
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can be used to synchronise access to resources among multiple light-weight
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processes.
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It causes the calling LWP to wait interruptably in the kernel, until one
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of the following conditions is met:
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.Bl -bullet
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.It
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The
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.Fa abstime
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argument is non-NULL, and the absolute UTC time it specifies has
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has passed.
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.It
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The LWP receives a directed signal posted using
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.Fn _lwp_kill ,
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or is elected to handle a signal on behalf of its containing process.
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.It
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The LWP is awoken by another LWP in the same process that has made
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a call to
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.Fn _lwp_wakeup .
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.It
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The LWP is awoken by another LWP in the same process that has made
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a call to
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.Fn _lwp_unpark
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or
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.Fn _lwp_unpark_all .
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.El
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.Pp
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The preferred method to awaken an LWP sleeping as a result of a call
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to
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.Fn _lwp_park
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is to make a call to
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.Fn _lwp_unpark ,
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or
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.Fn _lwp_unpark_all .
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The
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.Fn _lwp_wakeup
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system call is a more general facility, and requires more resources
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to execute.
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.Pp
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The
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.Fa uc
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argument is reserved, and for the current version of the system must
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be specified as
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.Dv NULL .
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The optional
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.Fa hint
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argument specifies the address of object upon which the LWP is
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synchronizing.
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When the
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.Fa hint
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2007-01-20 16:24:44 +03:00
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value is matched between calls to
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2007-01-20 04:41:00 +03:00
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.Fn _lwp_park
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and
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.Fn _lwp_unpark
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or
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.Fn _lwp_unpark_all ,
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it may reduce the time necessary for the system to resume execution
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of waiting LWPs.
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.Sh RETURN VALUES
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.Fn _lwp_park
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may return a value of 0.
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Otherwise, \-1 is returned and
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.Va errno
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is set to provide more information.
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.Sh ERRORS
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.Bl -tag -width [EINVAL]
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.It Bq Er ETIMEDOUT
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The UTC time specified by
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.Fa abstime
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has passed.
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.It Bq Er EINVAL
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The time value specified by
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.Fa abstime
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is invalid.
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.It Bq Er EINTR
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The LWP has been awoken by a signal or by a call to one of the
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following functions:
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.Fn _lwp_unpark ,
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.Fn _lwp_unpark_all ,
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.Fn _lwp_wakeup .
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.It Bq Er EALREADY
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A request was made to wake the LWP before it began to wait in
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the kernel.
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.El
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.Sh SEE ALSO
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.Xr _lwp_unpark 2 ,
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.Xr _lwp_unpark_all 2 ,
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.Xr _lwp_wakeup 2
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.Sh HISTORY
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The
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.Fn _lwp_park
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system call first appeared in
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.Nx 5.0 .
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