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| 1 | (**************************************************************************) |
| 2 | (* *) |
| 3 | (* OCaml *) |
| 4 | (* *) |
| 5 | (* Xavier Leroy and Damien Doligez, INRIA Rocquencourt *) |
| 6 | (* *) |
| 7 | (* Copyright 1996 Institut National de Recherche en Informatique et *) |
| 8 | (* en Automatique. *) |
| 9 | (* *) |
| 10 | (* All rights reserved. This file is distributed under the terms of *) |
| 11 | (* the GNU Lesser General Public License version 2.1, with the *) |
| 12 | (* special exception on linking described in the file LICENSE. *) |
| 13 | (* *) |
| 14 | (**************************************************************************) |
| 15 | |
| 16 | (** Condition variables to synchronize between threads. |
| 17 | |
| 18 | Condition variables are used when one thread wants to wait until another |
| 19 | thread has finished doing something: the former thread 'waits' on the |
| 20 | condition variable, the latter thread 'signals' the condition when it |
| 21 | is done. Condition variables should always be protected by a mutex. |
| 22 | The typical use is (if [D] is a shared data structure, [m] its mutex, |
| 23 | and [c] is a condition variable): |
| 24 | {[ |
| 25 | Mutex.lock m; |
| 26 | while (* some predicate P over D is not satisfied *) do |
| 27 | Condition.wait c m |
| 28 | done; |
| 29 | (* Modify D *) |
| 30 | if (* the predicate P over D is now satisfied *) then Condition.signal c; |
| 31 | Mutex.unlock m |
| 32 | ]} |
| 33 | *) |
| 34 | |
| 35 | type t |
| 36 | (** The type of condition variables. *) |
| 37 | |
| 38 | val create : unit -> t |
| 39 | (** Return a new condition variable. *) |
| 40 | |
| 41 | val wait : t -> Mutex.t -> unit |
| 42 | (** [wait c m] atomically unlocks the mutex [m] and suspends the |
| 43 | calling process on the condition variable [c]. The process will |
| 44 | restart after the condition variable [c] has been signalled. |
| 45 | The mutex [m] is locked again before [wait] returns. *) |
| 46 | |
| 47 | val signal : t -> unit |
| 48 | (** [signal c] restarts one of the processes waiting on the |
| 49 | condition variable [c]. *) |
| 50 | |
| 51 | val broadcast : t -> unit |
| 52 | (** [broadcast c] restarts all processes waiting on the |
| 53 | condition variable [c]. *) |
| 54 |