freebsd-dev/share/man/man9/sleep.9

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.\"
.\" Copyright (c) 1996 Joerg Wunsch
.\"
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.\" $Id: sleep.9,v 1.4 1996/04/06 13:33:23 joerg Exp $
.\" "
.Dd April 3, 1996
.Os
.Dt SLEEP 9
.Sh NAME
.Nm sleep ,
.Nm tsleep ,
.Nm wakeup
.Nd wait for events
.Sh SYNOPSIS
.Fd #include <sys/param.h>
.Fd #include <sys/systm.h>
.Fd #include <sys/proc.h>
.Fd #include <sys/errno.h>
.Ft int
.Fn tsleep "void *ident" "int priority" "char *wmesg" "int timo"
.Ft void
.Fn wakeup "void *ident"
.Ft int
.Fn sleep "void *ident" "int priority"
.Sh DESCRIPTION
The functions
.Fn tsleep
and
.Fn wakeup
handle event-based process blocking. If a process must wait for an
external event, it is put on sleep by
.Nm tsleep .
The parameter
.Ar ident
is an arbitrary address that uniquely identifies the event on which
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the process is being asleep. All processes sleeping on a single
.Ar ident
are woken up later by
.Nm wakeup ,
often called from inside an interrupt routine, to indicate that the
resource the process was blocking on is available now.
.Pp
The parameter
.Ar wmesg
is a string describing the sleep condition for tools like
.Xr ps 1 .
Due to the limited space of those programs to display arbitrary strings,
this message should not be longer than 6 characters.
.Pp
.Nm Tsleep
is the general sleep call. Suspends the current process until a wakeup is
performed on the specified identifier. The process will then be made
runnable with the specified
.Ar priority .
Sleeps at most
.Ar timo
\&/ hz seconds (0 means no timeout). If
.Ar pri
includes the
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.Dv PCATCH
flag, signals are checked before and after sleeping, else signals are
not checked. Returns 0 if awakened,
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.Dv EWOULDBLOCK
if the timeout expires. If
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.Dv PCATCH
is set and a signal needs to be delivered,
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.Dv ERESTART
is returned if the current system call should be restarted if
possible, and
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.Dv EINTR
is returned if the system call should be interrupted by the signal
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.Pq return Dv EINTR .
.Pp
.Nm Sleep
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is the traditional form. It doesn't let you specify a timeout nor a
.Ar wmesg ,
hence its use is deprecated.
.Sh RETURN VALUES
See above.
.Sh SEE ALSO
.Xr ps 1
.Sh HISTORY
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The sleep/wakeup process synchronization mechanism is very old. It
appeared in a very early version of Unix.
.Pp
.Nm Tsleep
appeared in
.Bx 4.4 .
.Sh AUTHORS
This man page has been written by
.ie t J\(:org Wunsch.
.el Joerg Wunsch.