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.Dd August 25, 2011 28.Dt SELRECORD 9 29.Os 30.Sh NAME 31.Nm seldrain , 32.Nm selrecord , 33.Nm selwakeup 34.Nd "record and wakeup select requests" 35.Sh SYNOPSIS 36.In sys/param.h 37.In sys/selinfo.h 38.Ft void 39.Fn seldrain "struct selinfo *sip" 40.Ft void 41.Fn selrecord "struct thread *td" "struct selinfo *sip" 42.Ft void 43.Fn selwakeup "struct selinfo *sip" 44.Sh DESCRIPTION 45.Fn seldrain , 46.Fn selrecord 47and 48.Fn selwakeup 49are the three central functions used by 50.Xr select 2 , 51.Xr poll 2 52and the objects that are being selected on. 53They handle the task of recording which threads are waiting on which objects 54and the waking of the proper threads when an event of interest occurs on an 55object. 56.Pp 57.Fn selrecord 58records that the calling thread is interested in events related to a given 59object. 60If another thread is already waiting on the object a collision will be flagged 61in 62.Fa sip 63which will be later dealt with by 64.Fn selwakeup . 65.Pp 66.Fn selrecord 67acquires and releases 68.Va sellock . 69.Pp 70.Fn selwakeup 71is called by the underlying object handling code in order to notify any waiting 72threads that an event of interest has occurred. 73If a collision has occurred, 74.Fn selwakeup 75will increment 76.Va nselcoll , 77and broadcast on the global cv in order to wake all waiting threads so that 78they can handle it. 79If the thread waiting on the object is not currently sleeping or the wait 80channel is not 81.Va selwait , 82.Fn selwakeup 83will clear the 84.Dv TDF_SELECT 85flag which should be noted by 86.Xr select 2 87and 88.Xr poll 2 89when they wake up. 90.Pp 91.Fn seldrain 92will flush the waiters queue on a specified object before its 93destruction. 94The object handling code must ensure that 95.Fa *sip 96cannot be used once 97.Fn seldrain 98has been called. 99.Pp 100The contents of 101.Fa *sip 102must be zeroed, such as by softc initialization, before any call to 103.Fn selrecord 104or 105.Fn selwakeup , 106otherwise a panic may occur. 107.Fn selwakeup 108acquires and releases 109.Va sellock 110and may acquire and release 111.Va sched_lock . 112.Fn seldrain 113could usually be just a wrapper for 114.Fn selwakeup , 115but consumers should not generally rely on this feature. 116.Sh SEE ALSO 117.Xr poll 2 , 118.Xr select 2 119.Sh AUTHORS 120.An -nosplit 121This manual page was written by 122.An Chad David Aq Mt davidc@FreeBSD.org 123and 124.An Alfred Perlstein Aq Mt alfred@FreeBSD.org . 125