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.\" Copyright (c) 2015 Mark Johnston <markj@FreeBSD.org>
.\"
.\" 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, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, 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 DEVELOPERS ``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 DEVELOPERS 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 November 7, 2015
.Dt PHOLD 9
.Os
.Sh NAME
.Nm PHOLD
.Nd hold a process
.Sh SYNOPSIS
.In sys/proc.h
.Fn PHOLD "struct proc *p"
.Fn _PHOLD "struct proc *p"
.Fn PRELE "struct proc *p"
.Fn _PRELE "struct proc *p"
.Fn PROC_ASSERT_HELD "struct proc *p"
.Fn PROC_ASSERT_NOT_HELD "struct proc *p"
.Sh DESCRIPTION
The
.Fn PHOLD
macro increments the hold count of a process, and the
.Fn PRELE
macro decrements the hold count of a process.
.Pp
If a process with a non-zero hold count attempts to exit, it will sleep until
its hold count has reached zero before the kernel begins releasing resources
associated with the process.
Once a process has started exiting, it is invalid to increase its hold count.
Thus, callers must not attempt to hold a process that has the
.Dv P_WEXIT
flag set.
The VM daemon will not swap out the kernel stack of a thread belonging to a
process with a non-zero hold count.
.Pp
The
.Fn _PHOLD
and
.Fn _PRELE
macros are identical to
.Fn PHOLD
and
.Fn PRELE ,
except that they must be called with the process lock held.
.Sh AUTHORS
This manual page was written by
.An Mark Johnston Aq Mt markj@FreeBSD.org .
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