gcc/ada/libgnarl/s-taspri__posix.ads

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                 GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS                 --
   4 --                                                                          --
   5 --               S Y S T E M . T A S K _ P R I M I T I V E S                --
   6 --                                                                          --
   7 --                                 S p e c                                  --
   8 --                                                                          --
   9 --            Copyright (C) 1991-2017, Florida State University             --
  10 --                     Copyright (C) 1995-2020, AdaCore                     --
  11 --                                                                          --
  12 -- GNAT is free software;  you can  redistribute it  and/or modify it under --
  13 -- terms of the  GNU General Public License as published  by the Free Soft- --
  14 -- ware  Foundation;  either version 3,  or (at your option) any later ver- --
  15 -- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
  16 -- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
  17 -- or FITNESS FOR A PARTICULAR PURPOSE.                                     --
  18 --                                                                          --
  19 -- As a special exception under Section 7 of GPL version 3, you are granted --
  20 -- additional permissions described in the GCC Runtime Library Exception,   --
  21 -- version 3.1, as published by the Free Software Foundation.               --
  22 --                                                                          --
  23 -- You should have received a copy of the GNU General Public License and    --
  24 -- a copy of the GCC Runtime Library Exception along with this program;     --
  25 -- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
  26 -- <http://www.gnu.org/licenses/>.                                          --
  27 --                                                                          --
  28 -- GNARL was developed by the GNARL team at Florida State University.       --
  29 -- Extensive contributions were provided by Ada Core Technologies, Inc.     --
  30 --                                                                          --
  31 ------------------------------------------------------------------------------
  32
  33 --  This is a POSIX-like version of this package
  34
  35 --  Note: this file can only be used for POSIX compliant systems
  36
  37 pragma Polling (Off);
  38 --  Turn off polling, we do not want ATC polling to take place during tasking
  39 --  operations. It causes infinite loops and other problems.
  40
  41 with System.OS_Interface;
  42
  43 package System.Task_Primitives is
  44    pragma Preelaborate;
  45
  46    type Lock is limited private;
  47    --  Should be used for implementation of protected objects
  48
  49    type RTS_Lock is limited private;
  50    --  Should be used inside the runtime system. The difference between Lock
  51    --  and the RTS_Lock is that the latter serves only as a semaphore so that
  52    --  we do not check for ceiling violations.
  53
  54    type Suspension_Object is limited private;
  55    --  Should be used for the implementation of Ada.Synchronous_Task_Control
  56
  57    type Task_Body_Access is access procedure;
  58    --  Pointer to the task body's entry point (or possibly a wrapper declared
  59    --  local to the GNARL).
  60
  61    type Private_Data is limited private;
  62    --  Any information that the GNULLI needs maintained on a per-task basis.
  63    --  A component of this type is guaranteed to be included in the
  64    --  Ada_Task_Control_Block.
  65
  66    subtype Task_Address is System.Address;
  67    Task_Address_Size : constant := Standard'Address_Size;
  68    --  Type used for task addresses and its size
  69
  70    Alternate_Stack_Size : constant := System.OS_Interface.Alternate_Stack_Size;
  71    --  Import value from System.OS_Interface
  72
  73 private
  74
  75    type RTS_Lock is new System.OS_Interface.pthread_mutex_t;
  76
  77    type Lock is record
  78       RW : aliased System.OS_Interface.pthread_rwlock_t;
  79       WO : aliased RTS_Lock;
  80    end record;
  81
  82    type Suspension_Object is record
  83       State : Boolean;
  84       pragma Atomic (State);
  85       --  Boolean that indicates whether the object is open. This field is
  86       --  marked Atomic to ensure that we can read its value without locking
  87       --  the access to the Suspension_Object.
  88
  89       Waiting : Boolean;
  90       --  Flag showing if there is a task already suspended on this object
  91
  92       L : aliased RTS_Lock;
  93       --  Protection for ensuring mutual exclusion on the Suspension_Object
  94
  95       CV : aliased System.OS_Interface.pthread_cond_t;
  96       --  Condition variable used to queue threads until condition is signaled
  97    end record;
  98
  99    type Private_Data is limited record
 100       Thread : aliased System.OS_Interface.pthread_t;
 101       pragma Atomic (Thread);
 102       --  Thread field may be updated by two different threads of control.
 103       --  (See, Enter_Task and Create_Task in s-taprop.adb). They put the same
 104       --  value (thr_self value). We do not want to use lock on those
 105       --  operations and the only thing we have to make sure is that they are
 106       --  updated in atomic fashion.
 107
 108       LWP : aliased System.Address;
 109       --  The purpose of this field is to provide a better tasking support on
 110       --  gdb. The order of the two first fields (Thread and LWP) is important.
 111       --  On targets where lwp is not relevant, this is equivalent to Thread.
 112
 113       CV : aliased System.OS_Interface.pthread_cond_t;
 114       --  Should be commented ??? (in all versions of taspri)
 115
 116       L : aliased RTS_Lock;
 117       --  Protection for all components is lock L
 118    end record;
 119
 120 end System.Task_Primitives;