gcc/ada/libgnarl/s-tpopsp__tls.adb

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                 GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS                 --
   4 --                                                                          --
   5 --                SYSTEM.TASK_PRIMITIVES.OPERATIONS.SPECIFIC                --
   6 --                                                                          --
   7 --                                B o d y                                   --
   8 --                                                                          --
   9 --         Copyright (C) 1992-2020, Free Software Foundation, Inc.          --
  10 --                                                                          --
  11 -- GNARL is free software; you can  redistribute it  and/or modify it under --
  12 -- terms of the  GNU General Public License as published  by the Free Soft- --
  13 -- ware  Foundation;  either version 3,  or (at your option) any later ver- --
  14 -- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
  15 -- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
  16 -- or FITNESS FOR A PARTICULAR PURPOSE.                                     --
  17 --                                                                          --
  18 -- As a special exception under Section 7 of GPL version 3, you are granted --
  19 -- additional permissions described in the GCC Runtime Library Exception,   --
  20 -- version 3.1, as published by the Free Software Foundation.               --
  21 --                                                                          --
  22 -- You should have received a copy of the GNU General Public License and    --
  23 -- a copy of the GCC Runtime Library Exception along with this program;     --
  24 -- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
  25 -- <http://www.gnu.org/licenses/>.                                          --
  26 --                                                                          --
  27 -- GNARL was developed by the GNARL team at Florida State University.       --
  28 -- Extensive contributions were provided by Ada Core Technologies, Inc.     --
  29 --                                                                          --
  30 ------------------------------------------------------------------------------
  31
  32 --  This is a version of this package using TLS and where foreign threads are
  33 --  recognized.
  34
  35 separate (System.Task_Primitives.Operations)
  36 package body Specific is
  37
  38    ATCB : aliased Task_Id := null;
  39    pragma Thread_Local_Storage (ATCB);
  40
  41    ----------------
  42    -- Initialize --
  43    ----------------
  44
  45    procedure Initialize (Environment_Task : Task_Id) is
  46    begin
  47       ATCB := Environment_Task;
  48    end Initialize;
  49
  50    -------------------
  51    -- Is_Valid_Task --
  52    -------------------
  53
  54    function Is_Valid_Task return Boolean is
  55    begin
  56       return ATCB /= null;
  57    end Is_Valid_Task;
  58
  59    ---------
  60    -- Set --
  61    ---------
  62
  63    procedure Set (Self_Id : Task_Id) is
  64    begin
  65       ATCB := Self_Id;
  66    end Set;
  67
  68    ----------
  69    -- Self --
  70    ----------
  71
  72    --  To make Ada tasks and C threads interoperate better, we have added some
  73    --  functionality to Self. Suppose a C main program (with threads) calls an
  74    --  Ada procedure and the Ada procedure calls the tasking runtime system.
  75    --  Eventually, a call will be made to self. Since the call is not coming
  76    --  from an Ada task, there will be no corresponding ATCB.
  77
  78    --  What we do in Self is to catch references that do not come from
  79    --  recognized Ada tasks, and create an ATCB for the calling thread.
  80
  81    --  The new ATCB will be "detached" from the normal Ada task master
  82    --  hierarchy, much like the existing implicitly created signal-server
  83    --  tasks.
  84
  85    function Self return Task_Id is
  86       Result : constant Task_Id := ATCB;
  87    begin
  88       if Result /= null then
  89          return Result;
  90       else
  91          --  If the value is Null then it is a non-Ada task
  92
  93          return Register_Foreign_Thread;
  94       end if;
  95    end Self;
  96
  97 end Specific;