mirror of
https://git.hardenedbsd.org/hardenedbsd/HardenedBSD.git
synced 2024-12-20 15:26:43 +01:00
127 lines
3.7 KiB
Groff
127 lines
3.7 KiB
Groff
.\"
|
|
.\" Copyright (C) 2002 Chad David <davidc@acns.ab.ca>. 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(s), this list of conditions and the following disclaimer as
|
|
.\" the first lines of this file unmodified other than the possible
|
|
.\" addition of one or more copyright notices.
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
|
.\" notice(s), 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 COPYRIGHT HOLDER(S) ``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 COPYRIGHT HOLDER(S) 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.
|
|
.\"
|
|
.\" $FreeBSD$
|
|
.\"
|
|
.Dd August 25, 2011
|
|
.Dt SELRECORD 9
|
|
.Os
|
|
.Sh NAME
|
|
.Nm seldrain ,
|
|
.Nm selrecord ,
|
|
.Nm selwakeup
|
|
.Nd "record and wakeup select requests"
|
|
.Sh SYNOPSIS
|
|
.In sys/param.h
|
|
.In sys/selinfo.h
|
|
.Ft void
|
|
.Fn seldrain "struct selinfo *sip"
|
|
.Ft void
|
|
.Fn selrecord "struct thread *td" "struct selinfo *sip"
|
|
.Ft void
|
|
.Fn selwakeup "struct selinfo *sip"
|
|
.Sh DESCRIPTION
|
|
.Fn seldrain ,
|
|
.Fn selrecord
|
|
and
|
|
.Fn selwakeup
|
|
are the three central functions used by
|
|
.Xr select 2 ,
|
|
.Xr poll 2
|
|
and the objects that are being selected on.
|
|
They handle the task of recording which threads are waiting on which objects
|
|
and the waking of the proper threads when an event of interest occurs on an
|
|
object.
|
|
.Pp
|
|
.Fn selrecord
|
|
records that the calling thread is interested in events related to a given
|
|
object.
|
|
If another thread is already waiting on the object a collision will be flagged
|
|
in
|
|
.Fa sip
|
|
which will be later dealt with by
|
|
.Fn selwakeup .
|
|
.Pp
|
|
.Fn selrecord
|
|
acquires and releases
|
|
.Va sellock .
|
|
.Pp
|
|
.Fn selwakeup
|
|
is called by the underlying object handling code in order to notify any waiting
|
|
threads that an event of interest has occurred.
|
|
If a collision has occurred,
|
|
.Fn selwakeup
|
|
will increment
|
|
.Va nselcoll ,
|
|
and broadcast on the global cv in order to wake all waiting threads so that
|
|
they can handle it.
|
|
If the thread waiting on the object is not currently sleeping or the wait
|
|
channel is not
|
|
.Va selwait ,
|
|
.Fn selwakeup
|
|
will clear the
|
|
.Dv TDF_SELECT
|
|
flag which should be noted by
|
|
.Xr select 2
|
|
and
|
|
.Xr poll 2
|
|
when they wake up.
|
|
.Pp
|
|
.Fn seldrain
|
|
will flush the waiters queue on a specified object before its
|
|
destruction.
|
|
The object handling code must ensure that
|
|
.Fa *sip
|
|
cannot be used once
|
|
.Fn seldrain
|
|
has been called.
|
|
.Pp
|
|
The contents of
|
|
.Fa *sip
|
|
must be zeroed, such as by softc initialization, before any call to
|
|
.Fn selrecord
|
|
or
|
|
.Fn selwakeup ,
|
|
otherwise a panic may occur.
|
|
.Fn selwakeup
|
|
acquires and releases
|
|
.Va sellock
|
|
and may acquire and release
|
|
.Va sched_lock .
|
|
.Fn seldrain
|
|
could usually be just a wrapper for
|
|
.Fn selwakeup ,
|
|
but consumers should not generally rely on this feature.
|
|
.Sh SEE ALSO
|
|
.Xr poll 2 ,
|
|
.Xr select 2
|
|
.Sh AUTHORS
|
|
.An -nosplit
|
|
This manual page was written by
|
|
.An Chad David Aq Mt davidc@FreeBSD.org
|
|
and
|
|
.An Alfred Perlstein Aq Mt alfred@FreeBSD.org .
|