+++ /dev/null
-------------------------------------------------------------------------------
--- --
--- GNAT RUN-TIME COMPONENTS --
--- --
--- G N A T . T A S K _ L O C K --
--- --
--- S p e c --
--- --
--- $Revision: 1.1 $
--- --
--- Copyright (C) 1998-2001 Ada Core Technologies, Inc. --
--- --
--- GNAT is free software; you can redistribute it and/or modify it under --
--- terms of the GNU General Public License as published by the Free Soft- --
--- ware Foundation; either version 2, or (at your option) any later ver- --
--- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
--- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
--- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
--- for more details. You should have received a copy of the GNU General --
--- Public License distributed with GNAT; see file COPYING. If not, write --
--- to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, --
--- MA 02111-1307, USA. --
--- --
--- 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 --
--- covered by the GNU General Public License. This exception does not --
--- however invalidate any other reasons why the executable file might be --
--- covered by the GNU Public License. --
--- --
--- GNAT is maintained by Ada Core Technologies Inc (http://www.gnat.com). --
--- --
-------------------------------------------------------------------------------
-
--- Simple task lock and unlock routines
-
--- A small package containing a task lock and unlock routines for creating
--- a critical region. The lock involved is a global lock, shared by all
--- tasks, and by all calls to these routines, so these routines should be
--- used with care to avoid unnecessary reduction of concurrency.
-
--- These routines may be used in a non-tasking program, and in that case
--- they have no effect (they do NOT cause the tasking runtime to be loaded).
-
-package GNAT.Task_Lock is
-pragma Elaborate_Body (Task_Lock);
-
- procedure Lock;
- pragma Inline (Lock);
- -- Acquires the global lock, starts the execution of a critical region
- -- which no other task can enter until the locking task calls Unlock
-
- procedure Unlock;
- pragma Inline (Unlock);
- -- Releases the global lock, allowing another task to successfully
- -- complete a Lock operation. Terminates the critical region.
-
- -- The recommended protocol for using these two procedures is as
- -- follows:
-
- -- Locked_Processing : begin
- -- Lock;
- -- ...
- -- TSL.Unlock;
- --
- -- exception
- -- when others =>
- -- Unlock;
- -- raise;
- -- end Locked_Processing;
-
- -- This ensures that the lock is not left set if an exception is raised
- -- explicitly or implicitly during the critical locked region.
-
- -- Note on multiple calls to Lock: It is permissible to call Lock
- -- more than once with no intervening Unlock from a single task,
- -- and the lock will not be released until the corresponding number
- -- of Unlock operations has been performed. For example:
-
- -- GNAT.Task_Lock.Lock; -- acquires lock
- -- GNAT.Task_Lock.Lock; -- no effect
- -- GNAT.Task_Lock.Lock; -- no effect
- -- GNAT.Task_Lock.Unlock; -- no effect
- -- GNAT.Task_Lock.Unlock; -- no effect
- -- GNAT.Task_Lock.Unlock; -- releases lock
-
- -- However, as previously noted, the Task_Lock facility should only
- -- be used for very local locks where the probability of conflict is
- -- low, so usually this kind of nesting is not a good idea in any case.
- -- In more complex locking situations, it is more appropriate to define
- -- an appropriate protected type to provide the required locking.
-
-end GNAT.Task_Lock;
projects / msp430-gcc.git / blobdiff