1.\" $NetBSD: kpreempt.9,v 1.3 2010/02/16 19:21:30 rmind Exp $ 2.\" 3.\" Copyright (c)2008 YAMAMOTO Takashi, 4.\" All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, 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 AUTHOR AND CONTRIBUTORS ``AS IS'' AND 16.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 17.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 18.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 19.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 20.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 21.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 22.\" HOWEVER 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 25.\" SUCH DAMAGE. 26.\" 27.\" ------------------------------------------------------------ 28.Dd February 16, 2010 29.Dt KPREEMPT 9 30.Os 31.\" ------------------------------------------------------------ 32.Sh NAME 33.Nm kpreempt 34.Nd control kernel preemption 35.\" ------------------------------------------------------------ 36.Sh SYNOPSIS 37.In sys/systm.h 38.\" - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 39.Ft void 40.Fn kpreempt_disable \ 41"void" 42.Ft void 43.Fn kpreempt_enable \ 44"void" 45.Ft bool 46.Fn kpreempt_disabled \ 47"void" 48.\" ------------------------------------------------------------ 49.Sh DESCRIPTION 50These functions are used to control kernel preemption of the calling LWP. 51.Pp 52On architectures where kernel preemption is not supported natively, these 53functions may still be used. 54.Pp 55It should be noted that kernel preemption is also disabled when holding 56the interrupt priority level above IPL_NONE, e.g. using 57.Xr spl 9 58or spinning 59.Xr mutex 9 60calls or holding kernel_lock (indicating that the code is not MT safe). 61.Pp 62.Fn kpreempt_disable 63disables kernel preemption of the calling LWP. 64Note that disabling kernel preemption can prevent LWPs with higher priorities 65from running. 66.Pp 67.Fn kpreempt_enable 68enables kernel preemption of the calling LWP, which was previously disabled by 69.Fn kpreempt_disable . 70.Pp 71.Fn kpreempt_disable 72and 73.Fn kpreempt_enable 74can be nested. 75.Pp 76.Fn kpreempt_disabled 77returns 78.Dv true 79if preemption of the calling LWP is disabled. 80It is only for diagnostic purpose. 81.\" ------------------------------------------------------------ 82.\" .Sh RETURN VALUES 83.\" ------------------------------------------------------------ 84.Sh SEE ALSO 85.Xr intro 9 , 86.Xr mutex 9 , 87.Xr spl 9 88