.TH RENDEZVOUS 3
.SH NAME
rendezvous \- user level process synchronization
.SH SYNOPSIS
.B #include <u.h>
.br
.B #include <libc.h>
.PP
.B
ulong rendezvous(ulong tag, ulong value)
.SH DESCRIPTION
The rendezvous system call allows two processes to synchronize and
exchange a value.
In conjunction with the shared memory system calls
(see
.IR segattach (3)
and
.IR fork (3)),
it enables parallel programs to control their scheduling.
.PP
Two processes wishing to synchronize call
.I rendezvous
with a common
.IR tag ,
typically an address in
memory they share.
One process will arrive at the rendezvous first;
it suspends execution until a second arrives.
When a second process meets the rendezvous
the
.I value
arguments are exchanged between the processes and returned
as the result of the respective
.I rendezvous
system calls.
Both processes are awakened when
the rendezvous succeeds.
.PP
The set of tag values which two processes may use to rendezvous\(emtheir tag space\(emis
inherited when a process forks, unless
.B RFREND
is set in the argument to
.BR rfork ;
see
.IR fork (3).
.PP
If a rendezvous is interrupted the return value is
.BR ~0 ,
so that value should not be used in normal communication.
.SH SOURCE
.B /usr/local/plan9/src/libc/9syscall
.SH SEE ALSO
.IR segattach (3),
.IR fork (3)
.SH DIAGNOSTICS
Sets
.IR errstr .