1.\" 2.\" Copyright (C) 2002 Chad David <davidc@acns.ab.ca>. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice(s), this list of conditions and the following disclaimer as 9.\" the first lines of this file unmodified other than the possible 10.\" addition of one or more copyright notices. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice(s), 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 COPYRIGHT HOLDER(S) ``AS IS'' AND ANY 16.\" EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 17.\" WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 18.\" DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY 19.\" DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 20.\" (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR 21.\" SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER 22.\" 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 SUCH 25.\" DAMAGE. 26.\" 27.\" $FreeBSD$ 28.\" 29.Dd August 25, 2011 30.Dt SELRECORD 9 31.Os 32.Sh NAME 33.Nm seldrain , 34.Nm selrecord , 35.Nm selwakeup 36.Nd "record and wakeup select requests" 37.Sh SYNOPSIS 38.In sys/param.h 39.In sys/selinfo.h 40.Ft void 41.Fn seldrain "struct selinfo *sip" 42.Ft void 43.Fn selrecord "struct thread *td" "struct selinfo *sip" 44.Ft void 45.Fn selwakeup "struct selinfo *sip" 46.Sh DESCRIPTION 47.Fn seldrain , 48.Fn selrecord 49and 50.Fn selwakeup 51are the three central functions used by 52.Xr select 2 , 53.Xr poll 2 54and the objects that are being selected on. 55They handle the task of recording which threads are waiting on which objects 56and the waking of the proper threads when an event of interest occurs on an 57object. 58.Pp 59.Fn selrecord 60records that the calling thread is interested in events related to a given 61object. 62If another thread is already waiting on the object a collision will be flagged 63in 64.Fa sip 65which will be later dealt with by 66.Fn selwakeup . 67.Pp 68.Fn selrecord 69acquires and releases 70.Va sellock . 71.Pp 72.Fn selwakeup 73is called by the underlying object handling code in order to notify any waiting 74threads that an event of interest has occurred. 75If a collision has occurred, 76.Fn selwakeup 77will increment 78.Va nselcoll , 79and broadcast on the global cv in order to wake all waiting threads so that 80they can handle it. 81If the thread waiting on the object is not currently sleeping or the wait 82channel is not 83.Va selwait , 84.Fn selwakeup 85will clear the 86.Dv TDF_SELECT 87flag which should be noted by 88.Xr select 2 89and 90.Xr poll 2 91when they wake up. 92.Pp 93.Fn seldrain 94will flush the waiters queue on a specified object before its 95destruction. 96The object handling code must ensure that 97.Fa *sip 98cannot be used once 99.Fn seldrain 100has been called. 101.Pp 102The contents of 103.Fa *sip 104must be zeroed, such as by softc initialization, before any call to 105.Fn selrecord 106or 107.Fn selwakeup , 108otherwise a panic may occur. 109.Fn selwakeup 110acquires and releases 111.Va sellock 112and may acquire and release 113.Va sched_lock . 114.Fn seldrain 115could usually be just a wrapper for 116.Fn selwakeup , 117but consumers should not generally rely on this feature. 118.Sh SEE ALSO 119.Xr poll 2 , 120.Xr select 2 121.Sh AUTHORS 122.An -nosplit 123This manual page was written by 124.An Chad David Aq davidc@FreeBSD.org 125and 126.An Alfred Perlstein Aq alfred@FreeBSD.org . 127