| ------------------------------------------------------------------------------ |
| -- -- |
| -- GNAT RUNTIME COMPONENTS -- |
| -- -- |
| -- 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 -- |
| -- -- |
| -- B o d y -- |
| -- -- |
| -- $Revision: 1.1 $ |
| -- -- |
| -- Copyright (C) 1992-2001 Free Software Foundation, 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 was originally developed by the GNAT team at New York University. -- |
| -- It is now maintained by Ada Core Technologies Inc (http://www.gnat.com). -- |
| -- -- |
| ------------------------------------------------------------------------------ |
| |
| with Interfaces.C; |
| package body Ada.Synchronous_Task_Control is |
| use System.OS_Interface; |
| use type Interfaces.C.int; |
| |
| ------------------- |
| -- Current_State -- |
| ------------------- |
| |
| function Current_State (S : Suspension_Object) return Boolean is |
| St : STATUS; |
| Result : Boolean := False; |
| |
| begin |
| -- Determine state by attempting to take the semaphore with |
| -- a 0 timeout value. Status = OK indicates the semaphore was |
| -- full, so reset it to the full state. |
| |
| St := semTake (S.Sema, NO_WAIT); |
| |
| if St = OK then |
| -- Took the semaphore. Reset semaphore state to FULL |
| Result := True; |
| St := semGive (S.Sema); |
| end if; |
| |
| return Result; |
| end Current_State; |
| |
| --------------- |
| -- Set_False -- |
| --------------- |
| |
| procedure Set_False (S : in out Suspension_Object) is |
| St : STATUS; |
| begin |
| -- Need to get the semaphore into the "empty" state. |
| -- On return, this task will have made the semaphore |
| -- empty (St = OK) or have left it empty. |
| St := semTake (S.Sema, NO_WAIT); |
| end Set_False; |
| |
| -------------- |
| -- Set_True -- |
| -------------- |
| |
| procedure Set_True (S : in out Suspension_Object) is |
| St : STATUS; |
| begin |
| St := semGive (S.Sema); |
| end Set_True; |
| |
| ------------------------ |
| -- Suspend_Until_True -- |
| ------------------------ |
| |
| procedure Suspend_Until_True (S : in out Suspension_Object) is |
| St : STATUS; |
| |
| -- Declare local exception so the mutex can still be reset |
| -- to full if Program_Error is raised |
| |
| Task_Already_Pending : exception; |
| begin |
| -- Determine whether another task is pending on the suspension |
| -- object. Should never be called from an ISR. Therefore semTake can |
| -- be called on the mutex |
| St := semTake (S.Mutex, NO_WAIT); |
| |
| if St = OK then |
| -- Wait for suspension object |
| |
| St := semTake (S.Sema, WAIT_FOREVER); |
| St := semGive (S.Mutex); |
| |
| else |
| -- Another task is pending on the suspension object |
| |
| raise Task_Already_Pending; |
| end if; |
| exception |
| when Task_Already_Pending => |
| raise Program_Error; |
| when others => |
| St := semGive (S.Mutex); |
| raise; |
| end Suspend_Until_True; |
| |
| procedure Initialize (S : in out Suspension_Object) is |
| begin |
| S.Sema := semBCreate (SEM_Q_FIFO, SEM_EMPTY); |
| |
| -- Use simpler binary semaphore instead of VxWorks |
| -- mutual exclusion semaphore, because we don't need |
| -- the fancier semantics and their overhead. |
| |
| S.Mutex := semBCreate (SEM_Q_FIFO, SEM_FULL); |
| end Initialize; |
| |
| procedure Finalize (S : in out Suspension_Object) is |
| St : STATUS; |
| begin |
| St := semDelete (S.Sema); |
| St := semDelete (S.Mutex); |
| end Finalize; |
| |
| end Ada.Synchronous_Task_Control; |
