88 lines
3.0 KiB
Groff
88 lines
3.0 KiB
Groff
.\" $NetBSD: kpreempt.9,v 1.3 2010/02/16 19:21:30 rmind Exp $
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.\"
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.\" Copyright (c)2008 YAMAMOTO Takashi,
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.\" All rights reserved.
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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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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" ------------------------------------------------------------
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.Dd February 16, 2010
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.Dt KPREEMPT 9
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.Os
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.\" ------------------------------------------------------------
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.Sh NAME
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.Nm kpreempt
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.Nd control kernel preemption
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.\" ------------------------------------------------------------
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.Sh SYNOPSIS
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.In sys/systm.h
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.\" - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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.Ft void
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.Fn kpreempt_disable \
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"void"
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.Ft void
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.Fn kpreempt_enable \
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"void"
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.Ft bool
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.Fn kpreempt_disabled \
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"void"
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.\" ------------------------------------------------------------
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.Sh DESCRIPTION
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These functions are used to control kernel preemption of the calling LWP.
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.Pp
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On architectures where kernel preemption is not supported natively, these
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functions may still be used.
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.Pp
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It should be noted that kernel preemption is also disabled when holding
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the interrupt priority level above IPL_NONE, e.g. using
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.Xr spl 9
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or spinning
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.Xr mutex 9
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calls or holding kernel_lock (indicating that the code is not MT safe).
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.Pp
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.Fn kpreempt_disable
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disables kernel preemption of the calling LWP.
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Note that disabling kernel preemption can prevent LWPs with higher priorities
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from running.
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.Pp
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.Fn kpreempt_enable
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enables kernel preemption of the calling LWP, which was previously disabled by
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.Fn kpreempt_disable .
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.Pp
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.Fn kpreempt_disable
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and
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.Fn kpreempt_enable
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can be nested.
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.Pp
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.Fn kpreempt_disabled
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returns
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.Dv true
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if preemption of the calling LWP is disabled.
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It is only for diagnostic purpose.
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.\" ------------------------------------------------------------
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.\" .Sh RETURN VALUES
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.\" ------------------------------------------------------------
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.Sh SEE ALSO
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.Xr intro 9 ,
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.Xr mutex 9 ,
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.Xr spl 9
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