otherlibs/threads/mutex.ml

   1 (***********************************************************************)
   2 (*                                                                     *)
   3 (*                           Objective Caml                            *)
   4 (*                                                                     *)
   5 (*         Xavier Leroy and Damien Doligez, INRIA Rocquencourt         *)
   6 (*                                                                     *)
   7 (*  Copyright 1996 Institut National de Recherche en Informatique et   *)
   8 (*  en Automatique.  All rights reserved.  This file is distributed    *)
   9 (*  under the terms of the GNU Library General Public License, with    *)
  10 (*  the special exception on linking described in file ../../LICENSE.  *)
  11 (*                                                                     *)
  12 (***********************************************************************)
  13
  14 (* $Id$ *)
  15
  16 type t = { mutable locked: bool; mutable waiting: Thread.t list }
  17
  18 let create () = { locked = false; waiting = [] }
  19
  20 let rec lock m =
  21   if m.locked then begin                (* test and set atomic *)
  22     Thread.critical_section := true;
  23     m.waiting <- Thread.self() :: m.waiting;
  24     Thread.sleep();
  25     lock m
  26   end else begin
  27     m.locked <- true                    (* test and set atomic *)
  28   end
  29
  30 let try_lock m =                        (* test and set atomic *)
  31   if m.locked then false else begin m.locked <- true; true end
  32
  33 let unlock m =
  34   (* Don't play with Thread.critical_section here because of Condition.wait *)
  35   let w = m.waiting in                  (* atomic *)
  36   m.waiting <- [];                      (* atomic *)
  37   m.locked <- false;                    (* atomic *)
  38   List.iter Thread.wakeup w
  39