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.TH RENDEZVOUS 2
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.SH NAME
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rendezvous \- user level process synchronization
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.SH SYNOPSIS
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.B #include <u.h>
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.br
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.B #include <libc.h>
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.PP
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.B
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void* rendezvous(void* tag, void* value)
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.SH DESCRIPTION
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The rendezvous system call allows two processes to synchronize and
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exchange a value.
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In conjunction with the shared memory system calls
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(see
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.IR segattach (2)
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and
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.IR fork (2)),
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it enables parallel programs to control their scheduling.
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.PP
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Two processes wishing to synchronize call
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.I rendezvous
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with a common
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.IR tag ,
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typically an address in
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memory they share.
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One process will arrive at the rendezvous first;
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it suspends execution until a second arrives.
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When a second process meets the rendezvous
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the
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.I value
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arguments are exchanged between the processes and returned
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as the result of the respective
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.I rendezvous
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system calls.
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Both processes are awakened when
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the rendezvous succeeds.
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.PP
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The set of tag values which two processes may use to rendezvous\(emtheir tag space\(emis
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inherited when a process forks, unless
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.B RFREND
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is set in the argument to
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.BR rfork ;
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see
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.IR fork (2).
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.PP
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If a rendezvous is interrupted the return value is
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.BR ~0 ,
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so that value should not be used in normal communication.
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.SH SOURCE
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.B /sys/src/libc/9syscall
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.SH SEE ALSO
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.IR fork (2),
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.IR lock (2),
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.IR segattach (2)
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.SH DIAGNOSTICS
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Sets
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.IR errstr .