------------------------------------------------------------------------------
--                                                                          --
--                         GNAT COMPILER COMPONENTS                         --
--                                                                          --
--                  S Y S T E M . G L O B A L _ L O C K S                   --
--                                                                          --
--                                 S p e c                                  --
--                                                                          --
--                            $Revision: 1.1 $
--                                                                          --
--           Copyright (C) 1999-2001 Ada Core Technologies, Inc.            --
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-- GNAT is free software;  you can  redistribute it  and/or modify it under --
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-- MA 02111-1307, USA.                                                      --
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-- As a special exception,  if other files  instantiate  generics from this --
-- unit, or you link  this unit with other files  to produce an executable, --
-- this  unit  does not  by itself cause  the resulting  executable  to  be --
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-- covered by the  GNU Public License.                                      --
--                                                                          --
-- GNAT is maintained by Ada Core Technologies Inc (http://www.gnat.com).   --
--                                                                          --
------------------------------------------------------------------------------

   --  This package contains the necessary routines to provide
   --  reliable system wide locking capability.

package System.Global_Locks is

   Lock_Error : exception;
   --  Exception raised if a request cannot be executed on a lock.

   type Lock_Type is private;
   --  Such a lock is a global lock between partitions. This lock is
   --  uniquely defined between the partitions because of its name.

   Null_Lock : constant Lock_Type;

   procedure Create_Lock
     (Lock : out Lock_Type;
      Name : in String);
   --  Create or retrieve a global lock for the current partition using
   --  its Name.

   procedure Acquire_Lock
     (Lock : in out Lock_Type);
   --  If the lock cannot be acquired because someone already owns it, this
   --  procedure is supposed to wait and retry forever.

   procedure Release_Lock
     (Lock : in out Lock_Type);

private

   type Lock_Type is new Natural;

   Null_Lock : constant Lock_Type := 0;

end System.Global_Locks;
