RENDEZVOUS(2)                                       RENDEZVOUS(2)

     NAME
          rendezvous - user level process synchronization

     SYNOPSIS
          #include <u.h>
          #include <libc.h>

          void* rendezvous(void* tag, void* value)

     DESCRIPTION
          The rendezvous system call allows two processes to synchro-
          nize and exchange a value.  In conjunction with the shared
          memory system calls (see segattach(2) and fork(2)), it
          enables parallel programs to control their scheduling.

          Two processes wishing to synchronize call rendezvous with a
          common 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 value arguments are exchanged
          between the processes and returned as the result of the
          respective rendezvous system calls.  Both processes are
          awakened when the rendezvous succeeds.

          The set of tag values which two processes may use to
          rendezvous-their tag space-is inherited when a process
          forks, unless RFREND is set in the argument to rfork; see
          fork(2).

          If a rendezvous is interrupted the return value is ~0, so
          that value should not be used in normal communication.

     SOURCE
          /sys/src/libc/9syscall

     SEE ALSO
          fork(2), lock(2), segattach(2)

     DIAGNOSTICS
          Sets errstr.