.\"	$NetBSD: kpause.9,v 1.8 2013/10/17 13:17:50 gson Exp $
.\"
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.\" This code is derived from software contributed to The NetBSD Foundation
.\" by Andrew Doran.
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.\" ------------------------------------------------------------
.Dd July 20, 2011
.Dt KPAUSE 9
.Os
.\" ------------------------------------------------------------
.Sh NAME
.Nm kpause
.Nd make the calling LWP sleep
.\" ------------------------------------------------------------
.Sh SYNOPSIS
.In sys/proc.h
.\" - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
.Ft int
.Fn kpause \
"const char *wmesg" "bool intr" "int timeo" "kmutex_t *mtx"
.\" ------------------------------------------------------------
.Sh DESCRIPTION
.Fn kpause
makes the calling LWP sleep.
It's similar to
.Xr cv_timedwait_sig 9
without the corresponding
.Xr cv_signal 9 .
.Pp
.Fn kpause
can wake up spontaneously.
Callers should prepare to handle it.
.Pp
.Bl -tag -width wmesg
.It Fa wmesg
Specifies a string of no more than 8 characters that describes
the resource or condition associated with the call of
.Fn kpause .
The kernel does not use this argument directly but makes it available for
utilities such as
.Xr ps 1
to display.
.It Fa intr
If true, sleep interruptably.
If the LWP receives a signal, or is interrupted by another condition such
as its containing process exiting, the wait is ended early and an error
code returned.
.It Fa timeo
Specify a timeout.
It is an architecture and system dependent value related to the number of
clock interrupts per second.
See
.Xr hz 9
for details.
The
.Xr mstohz 9
macro can be used to convert a timeout expressed in milliseconds to
one suitable for
.Fn kpause .
.Pp
Zero means no timeout.
.It Fa mtx
Convenience and symmetry with other synchronization operations.
If not
.Dv NULL ,
.Fa mtx
will be released once the LWP has prepared to sleep, and will be reacquired
before
.Fn kpause
returns.
.El
.\" ------------------------------------------------------------
.Sh RETURN VALUES
.Fn kpause
returns 0 when waking up spontaneously.
Otherwise,
it returns an error number.
.\" ------------------------------------------------------------
.Sh ERRORS
.Bl -tag -width Er
.It Bq Er EINTR
.Fn kpause
returned due to other reasons.
Typically as a result of a signal without
.Dv SA_RESTART
property.
.It Bq Er ERESTART
.Fn kpause
returned as a result of a signal with
.Dv SA_RESTART
property.
.It Bq Er EWOULDBLOCK
The timeout expired.
.El
.\" ------------------------------------------------------------
.Sh SEE ALSO
.Xr sigaction 2 ,
.Xr condvar 9 ,
.Xr delay 9 ,
.Xr errno 9 ,
.Xr hz 9 ,
.Xr mstohz 9