.TH "Condition" 3o 2023-09-18 OCamldoc "OCaml library"
.SH NAME
Condition \- Condition variables to synchronize between threads.
.SH Module
Module   Condition
.SH Documentation
.sp
Module
.BI "Condition"
 : 
.B sig end

.sp
Condition variables to synchronize between threads\&.
.sp
Condition variables are used when one thread wants to wait until another
thread has finished doing something: the former thread \&'waits\&' on the
condition variable, the latter thread \&'signals\&' the condition when it
is done\&. Condition variables should always be protected by a mutex\&.
The typical use is (if 
.ft B
D
.ft R
is a shared data structure, 
.ft B
m
.ft R
its mutex,
and 
.ft B
c
.ft R
is a condition variable):
.EX
.ft B
.br
\&     Mutex\&.lock m;
.br
\&     while (* some predicate P over D is not satisfied *) do
.br
\&       Condition\&.wait c m
.br
\&     done;
.br
\&     (* Modify D *)
.br
\&     if (* the predicate P over D is now satisfied *) then Condition\&.signal c;
.br
\&     Mutex\&.unlock m
.br
\&   
.ft R
.EE

.sp

.sp
.sp
.I type t 

.sp
The type of condition variables\&.

.sp

.I val create 
: 
.B unit -> t
.sp
Return a new condition variable\&.

.sp

.I val wait 
: 
.B t -> Mutex.t -> unit
.sp

.ft B
wait c m
.ft R
atomically unlocks the mutex 
.ft B
m
.ft R
and suspends the
calling process on the condition variable 
.ft B
c
.ft R
\&. The process will
restart after the condition variable 
.ft B
c
.ft R
has been signalled\&.
The mutex 
.ft B
m
.ft R
is locked again before 
.ft B
wait
.ft R
returns\&.

.sp

.I val signal 
: 
.B t -> unit
.sp

.ft B
signal c
.ft R
restarts one of the processes waiting on the
condition variable 
.ft B
c
.ft R
\&.

.sp

.I val broadcast 
: 
.B t -> unit
.sp

.ft B
broadcast c
.ft R
restarts all processes waiting on the
condition variable 
.ft B
c
.ft R
\&.

.sp