gcc/ada/libgnarl/g-thread.ads

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT RUN-TIME COMPONENTS                         --
   4 --                                                                          --
   5 --                         G N A T . T H R E A D S                          --
   6 --                                                                          --
   7 --                                 S p e c                                  --
   8 --                                                                          --
   9 --                     Copyright (C) 1998-2020, AdaCore                     --
  10 --                                                                          --
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  16 -- or FITNESS FOR A PARTICULAR PURPOSE.                                     --
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  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 -- GNAT was originally developed  by the GNAT team at  New York University. --
  28 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  29 --                                                                          --
  30 ------------------------------------------------------------------------------
  31
  32 --  This package provides facilities for creation or registration of foreign
  33 --  threads for use as Ada tasks. In order to execute general Ada code, the
  34 --  run-time system must know about all tasks. This package allows foreign
  35 --  code, e.g. a C program, to create a thread that the Ada run-time knows
  36 --  about, or to register the current thread.
  37
  38 --  For some implementations of GNAT Pro, the registration of foreign threads
  39 --  is automatic. However, in such implementations, if the Ada program has no
  40 --  tasks at all and no tasking constructs other than delay, then by default
  41 --  the non-tasking version of the Ada run-time will be loaded. If foreign
  42 --  threads are present, it is important to ensure that the tasking version
  43 --  of the Ada run time is loaded. This may be achieved by adding "with
  44 --  GNAT.Threads" to any unit in the partition.
  45
  46 with System;
  47 with Ada.Task_Identification;
  48
  49 package GNAT.Threads is
  50
  51    type Void_Ptr is access all Integer;
  52
  53    function Create_Thread
  54      (Code : System.Address;  -- pointer
  55       Parm : Void_Ptr;        -- pointer
  56       Size : Natural;         -- int
  57       Prio : Integer)         -- int
  58       return System.Address;
  59    pragma Export (C, Create_Thread, "__gnat_create_thread");
  60    --  Creates a thread with the given (Size) stack size in bytes, and
  61    --  the given (Prio) priority. The task will execute a call to the
  62    --  procedure whose address is given by Code. This procedure has
  63    --  the prototype
  64    --
  65    --    void thread_code (void *id, void *parm);
  66    --
  67    --  where id is the id of the created task, and parm is the parameter
  68    --  passed to Create_Thread. The called procedure is the body of the
  69    --  code for the task, the task will be automatically terminated when
  70    --  the procedure returns.
  71    --
  72    --  This function returns the Ada Id of the created task that can then be
  73    --  used as a parameter to the procedures below.
  74    --
  75    --  C declaration:
  76    --
  77    --  extern void *__gnat_create_thread
  78    --    (void (*code)(void *, void *), void *parm, int size, int prio);
  79
  80    function Register_Thread return System.Address;
  81    pragma Export (C, Register_Thread, "__gnat_register_thread");
  82    --  Create an Ada task Id for the current thread if needed.
  83    --  If the thread could not be registered, System.Null_Address is returned.
  84    --
  85    --  This function returns the Ada Id of the current task that can then be
  86    --  used as a parameter to the procedures below.
  87    --
  88    --  C declaration:
  89    --
  90    --  extern void *__gnat_register_thread ();
  91    --
  92    --  Here is a typical usage of the Register/Unregister_Thread procedures:
  93    --
  94    --  void thread_body ()
  95    --  {
  96    --    void *task_id = __gnat_register_thread ();
  97    --    ... thread body ...
  98    --    __gnat_unregister_thread ();
  99    --  }
 100
 101    procedure Unregister_Thread;
 102    pragma Export (C, Unregister_Thread, "__gnat_unregister_thread");
 103    --  Unregister the current task from the GNAT run time and destroy the
 104    --  memory allocated for its task id.
 105    --
 106    --  C declaration:
 107    --
 108    --  extern void __gnat_unregister_thread ();
 109
 110    procedure Unregister_Thread_Id (Thread : System.Address);
 111    pragma Export (C, Unregister_Thread_Id, "__gnat_unregister_thread_id");
 112    --  Unregister the task associated with Thread from the GNAT run time and
 113    --  destroy the memory allocated for its task id.
 114    --  If no task id is associated with Thread, do nothing.
 115    --
 116    --  C declaration:
 117    --
 118    --  extern void __gnat_unregister_thread_id (pthread_t *thread);
 119
 120    procedure Destroy_Thread (Id : System.Address);
 121    pragma Export (C, Destroy_Thread, "__gnat_destroy_thread");
 122    --  This procedure may be used to prematurely abort the created thread.
 123    --  The value Id is the value that was passed to the thread code procedure
 124    --  at activation time.
 125    --
 126    --  C declaration:
 127    --
 128    --  extern void __gnat_destroy_thread (void *id);
 129
 130    procedure Get_Thread (Id : System.Address; Thread : System.Address);
 131    pragma Export (C, Get_Thread, "__gnat_get_thread");
 132    procedure Get_Thread
 133      (Id : Ada.Task_Identification.Task_Id; Thread : System.Address);
 134    --  This procedure is used to retrieve the thread id of a given task.
 135    --  The value Id is the value that was passed to the thread code procedure
 136    --  at activation time or a Task_Id.
 137    --  Thread is a pointer to a thread id that will be updated by this
 138    --  procedure.
 139    --
 140    --  C declaration:
 141    --
 142    --  extern void __gnat_get_thread (void *id, pthread_t *thread);
 143
 144    function To_Task_Id
 145      (Id : System.Address)
 146       return Ada.Task_Identification.Task_Id;
 147    --  Ada interface only.
 148    --  Given a low level Id, as returned by Create_Thread, return a Task_Id,
 149    --  so that operations in Ada.Task_Identification can be used.
 150
 151    function Make_Independent return Boolean;
 152    --  If a procedure loads a shared library containing tasks, and that
 153    --  procedure is considered to be a master by the compiler (because it
 154    --  contains tasks or class-wide objects that might contain tasks),
 155    --  then the tasks in the shared library need to call Make_Independent
 156    --  because otherwise they will depend on the procedure that loaded the
 157    --  shared library.
 158    --
 159    --  See System.Tasking.Utilities.Make_Independent in s-tasuti.ads for
 160    --  further documentation.
 161
 162 end GNAT.Threads;