------------------------------------------------------------------------------ -- -- -- GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS -- -- -- -- S Y S T E M . T A S K I N G . I N I T I A L I Z A T I O N -- -- -- -- S p e c -- -- -- -- Copyright (C) 1992-2012, Free Software Foundation, Inc. -- -- -- -- GNARL 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 3, 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. -- -- -- -- As a special exception under Section 7 of GPL version 3, you are granted -- -- additional permissions described in the GCC Runtime Library Exception, -- -- version 3.1, as published by the Free Software Foundation. -- -- -- -- You should have received a copy of the GNU General Public License and -- -- a copy of the GCC Runtime Library Exception along with this program; -- -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see -- -- . -- -- -- -- GNARL was developed by the GNARL team at Florida State University. -- -- Extensive contributions were provided by Ada Core Technologies, Inc. -- -- -- ------------------------------------------------------------------------------ -- This package provides overall initialization of the tasking portion of the -- RTS. This package must be elaborated before any tasking features are used. package System.Tasking.Initialization is procedure Remove_From_All_Tasks_List (T : Task_Id); -- Remove T from All_Tasks_List. Call this function with RTS_Lock taken --------------------------------- -- Tasking-Specific Soft Links -- --------------------------------- -- These permit us to leave out certain portions of the tasking -- run-time system if they are not used. They are only used internally -- by the tasking run-time system. -- So far, the only example is support for Ada.Task_Attributes type Proc_T is access procedure (T : Task_Id); procedure Finalize_Attributes (T : Task_Id); procedure Initialize_Attributes (T : Task_Id); Finalize_Attributes_Link : Proc_T := Finalize_Attributes'Access; -- should be called with abort deferred and T.L write-locked Initialize_Attributes_Link : Proc_T := Initialize_Attributes'Access; -- should be called with abort deferred, but holding no locks ------------------------- -- Abort Defer/Undefer -- ------------------------- -- Defer_Abort defers the effects of low-level abort and priority change -- in the calling task until a matching Undefer_Abort call is executed. -- Undefer_Abort DOES MORE than just undo the effects of one call to -- Defer_Abort. It is the universal "polling point" for deferred -- processing, including the following: -- 1) base priority changes -- 2) abort/ATC -- Abort deferral MAY be nested (Self_ID.Deferral_Level is a count), but -- to avoid waste and undetected errors, it generally SHOULD NOT be -- nested. The symptom of over-deferring abort is that an exception may -- fail to be raised, or an abort may fail to take place. -- Therefore, there are two sets of the inlineable defer/undefer routines, -- which are the ones to be used inside GNARL. One set allows nesting. The -- other does not. People who maintain the GNARL should try to avoid using -- the nested versions, or at least look very critically at the places -- where they are used. -- In general, any GNARL call that is potentially blocking, or whose -- semantics require that it sometimes raise an exception, or that is -- required to be an abort completion point, must be made with abort -- Deferral_Level = 1. -- In general, non-blocking GNARL calls, which may be made from inside a -- protected action, are likely to need to allow nested abort deferral. -- With some critical exceptions (which are supposed to be documented), -- internal calls to the tasking runtime system assume abort is already -- deferred, and do not modify the deferral level. -- There is also a set of non-inlineable defer/undefer routines, for direct -- call from the compiler. These are not inlineable because they may need -- to be called via pointers ("soft links"). For the sake of efficiency, -- the version with Self_ID as parameter should used wherever possible. -- These are all nestable. -- Non-nestable inline versions procedure Defer_Abort (Self_ID : Task_Id); pragma Inline (Defer_Abort); procedure Undefer_Abort (Self_ID : Task_Id); pragma Inline (Undefer_Abort); -- Nestable inline versions procedure Defer_Abort_Nestable (Self_ID : Task_Id); pragma Inline (Defer_Abort_Nestable); procedure Undefer_Abort_Nestable (Self_ID : Task_Id); pragma Inline (Undefer_Abort_Nestable); procedure Do_Pending_Action (Self_ID : Task_Id); -- Only call with no locks, and when Self_ID.Pending_Action = True Perform -- necessary pending actions (e.g. abort, priority change). This procedure -- is usually called when needed as a result of calling Undefer_Abort, -- although in the case of e.g. No_Abort restriction, it can be necessary -- to force execution of pending actions. function Check_Abort_Status return Integer; -- Returns Boolean'Pos (True) iff abort signal should raise -- Standard'Abort_Signal. Only used by IRIX currently. -------------------------- -- Change Base Priority -- -------------------------- procedure Change_Base_Priority (T : Task_Id); -- Change the base priority of T. Has to be called with the affected -- task's ATCB write-locked. May temporarily release the lock. ---------------------- -- Task Lock/Unlock -- ---------------------- procedure Task_Lock (Self_ID : Task_Id); pragma Inline (Task_Lock); procedure Task_Unlock (Self_ID : Task_Id); pragma Inline (Task_Unlock); -- These are versions of Lock_Task and Unlock_Task created for use -- within the GNARL. procedure Final_Task_Unlock (Self_ID : Task_Id); -- This version is only for use in Terminate_Task, when the task is -- relinquishing further rights to its own ATCB. There is a very -- interesting potential race condition there, where the old task may run -- concurrently with a new task that is allocated the old tasks (now -- reused) ATCB. The critical thing here is to not make any reference to -- the ATCB after the lock is released. See also comments on -- Terminate_Task and Unlock. procedure Wakeup_Entry_Caller (Self_ID : Task_Id; Entry_Call : Entry_Call_Link; New_State : Entry_Call_State); pragma Inline (Wakeup_Entry_Caller); -- This is called at the end of service of an entry call, to abort the -- caller if he is in an abortable part, and to wake up the caller if he -- is on Entry_Caller_Sleep. Call it holding the lock of Entry_Call.Self. -- -- Timed_Call or Simple_Call: -- The caller is waiting on Entry_Caller_Sleep, in Wait_For_Completion, -- or Wait_For_Completion_With_Timeout. -- -- Conditional_Call: -- The caller might be in Wait_For_Completion, -- waiting for a rendezvous (possibly requeued without abort) to -- complete. -- -- Asynchronous_Call: -- The caller may be executing in the abortable part an async. select, -- or on a time delay, if Entry_Call.State >= Was_Abortable. procedure Locked_Abort_To_Level (Self_ID : Task_Id; T : Task_Id; L : ATC_Level); pragma Inline (Locked_Abort_To_Level); -- Abort a task to a specified ATC level. Call this only with T locked end System.Tasking.Initialization;