1 ------------------------------------------------------------------------------
3 -- GNAT RUNTIME COMPONENTS --
5 -- A D A . S Y N C H R O N O U S _ T A S K _ C O N T R O L --
11 -- Copyright (C) 1992-2001 Free Software Foundation, Inc. --
13 -- GNAT is free software; you can redistribute it and/or modify it under --
14 -- terms of the GNU General Public License as published by the Free Soft- --
15 -- ware Foundation; either version 2, or (at your option) any later ver- --
16 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
17 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
18 -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
19 -- for more details. You should have received a copy of the GNU General --
20 -- Public License distributed with GNAT; see file COPYING. If not, write --
21 -- to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, --
22 -- MA 02111-1307, USA. --
24 -- As a special exception, if other files instantiate generics from this --
25 -- unit, or you link this unit with other files to produce an executable, --
26 -- this unit does not by itself cause the resulting executable to be --
27 -- covered by the GNU General Public License. This exception does not --
28 -- however invalidate any other reasons why the executable file might be --
29 -- covered by the GNU Public License. --
31 -- GNAT was originally developed by the GNAT team at New York University. --
32 -- It is now maintained by Ada Core Technologies Inc (http://www.gnat.com). --
34 ------------------------------------------------------------------------------
37 package body Ada.Synchronous_Task_Control is
38 use System.OS_Interface;
39 use type Interfaces.C.int;
45 function Current_State (S : Suspension_Object) return Boolean is
47 Result : Boolean := False;
50 -- Determine state by attempting to take the semaphore with
51 -- a 0 timeout value. Status = OK indicates the semaphore was
52 -- full, so reset it to the full state.
54 St := semTake (S.Sema, NO_WAIT);
57 -- Took the semaphore. Reset semaphore state to FULL
59 St := semGive (S.Sema);
69 procedure Set_False (S : in out Suspension_Object) is
72 -- Need to get the semaphore into the "empty" state.
73 -- On return, this task will have made the semaphore
74 -- empty (St = OK) or have left it empty.
75 St := semTake (S.Sema, NO_WAIT);
82 procedure Set_True (S : in out Suspension_Object) is
85 St := semGive (S.Sema);
88 ------------------------
89 -- Suspend_Until_True --
90 ------------------------
92 procedure Suspend_Until_True (S : in out Suspension_Object) is
95 -- Declare local exception so the mutex can still be reset
96 -- to full if Program_Error is raised
98 Task_Already_Pending : exception;
100 -- Determine whether another task is pending on the suspension
101 -- object. Should never be called from an ISR. Therefore semTake can
102 -- be called on the mutex
103 St := semTake (S.Mutex, NO_WAIT);
106 -- Wait for suspension object
108 St := semTake (S.Sema, WAIT_FOREVER);
109 St := semGive (S.Mutex);
112 -- Another task is pending on the suspension object
114 raise Task_Already_Pending;
117 when Task_Already_Pending =>
120 St := semGive (S.Mutex);
122 end Suspend_Until_True;
124 procedure Initialize (S : in out Suspension_Object) is
126 S.Sema := semBCreate (SEM_Q_FIFO, SEM_EMPTY);
128 -- Use simpler binary semaphore instead of VxWorks
129 -- mutual exclusion semaphore, because we don't need
130 -- the fancier semantics and their overhead.
132 S.Mutex := semBCreate (SEM_Q_FIFO, SEM_FULL);
135 procedure Finalize (S : in out Suspension_Object) is
138 St := semDelete (S.Sema);
139 St := semDelete (S.Mutex);
142 end Ada.Synchronous_Task_Control;