gcc/ada/libgnarl/s-tposen.ads

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                 GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS                 --
   4 --                                                                          --
   5 --               SYSTEM.TASKING.PROTECTED_OBJECTS.SINGLE_ENTRY              --
   6 --                                                                          --
   7 --                                  S p e c                                 --
   8 --                                                                          --
   9 --          Copyright (C) 1992-2017, Free Software Foundation, Inc.         --
  10 --                                                                          --
  11 -- GNAT 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 package provides an optimized version of Protected_Objects.Operations
  33 --  and Protected_Objects.Entries making the following assumptions:
  34
  35 --    PO have only one entry
  36 --    There is only one caller at a time (No_Entry_Queue)
  37 --    There is no dynamic priority support (No_Dynamic_Priorities)
  38 --    No Abort Statements
  39 --      (No_Abort_Statements, Max_Asynchronous_Select_Nesting => 0)
  40 --    PO are at library level
  41 --    None of the tasks will terminate (no need for finalization)
  42
  43 --  This interface is intended to be used in the Ravenscar profile, the
  44 --  compiler is responsible for ensuring that the conditions mentioned above
  45 --  are respected, except for the No_Entry_Queue restriction that is checked
  46 --  dynamically in this package, since the check cannot be performed at compile
  47 --  time, and is relatively cheap (see body).
  48
  49 --  This package is part of the high level tasking interface used by the
  50 --  compiler to expand Ada 95 tasking constructs into simpler run time calls
  51 --  (aka GNARLI, GNU Ada Run-time Library Interface)
  52
  53 --  Note: the compiler generates direct calls to this interface, via Rtsfind.
  54 --  Any changes to this interface may require corresponding compiler changes
  55 --  in exp_ch9.adb and possibly exp_ch7.adb
  56
  57 package System.Tasking.Protected_Objects.Single_Entry is
  58    pragma Elaborate_Body;
  59
  60    ---------------------------------
  61    -- Compiler Interface (GNARLI) --
  62    ---------------------------------
  63
  64    --  The compiler will expand in the GNAT tree the following construct:
  65
  66    --  protected PO is
  67    --     entry E;
  68    --     procedure P;
  69    --  private
  70    --     Open : Boolean := False;
  71    --  end PO;
  72
  73    --  protected body PO is
  74    --     entry E when Open is
  75    --        ...variable declarations...
  76    --     begin
  77    --        ...B...
  78    --     end E;
  79
  80    --     procedure P is
  81    --        ...variable declarations...
  82    --     begin
  83    --        ...C...
  84    --     end P;
  85    --  end PO;
  86
  87    --  as follows:
  88
  89    --  protected type poT is
  90    --     entry e;
  91    --     procedure p;
  92    --  private
  93    --     open : boolean := false;
  94    --  end poT;
  95    --  type poTV is limited record
  96    --     open : boolean := false;
  97    --     _object : aliased protection_entry;
  98    --  end record;
  99    --  procedure poPT__E1s (O : address; P : address; E :
 100    --    protected_entry_index);
 101    --  function poPT__B2s (O : address; E : protected_entry_index) return
 102    --    boolean;
 103    --  procedure poPT__pN (_object : in out poTV);
 104    --  procedure poPT__pP (_object : in out poTV);
 105    --  poTA : aliased entry_body := (
 106    --     barrier => poPT__B2s'unrestricted_access,
 107    --     action => poPT__E1s'unrestricted_access);
 108    --  freeze poTV [
 109    --     procedure poTVIP (_init : in out poTV) is
 110    --     begin
 111    --        _init.open := false;
 112    --        object-init-proc (_init._object);
 113    --        initialize_protection_entry (_init._object'unchecked_access,
 114    --          unspecified_priority, _init'address, poTA'
 115    --          unrestricted_access);
 116    --        return;
 117    --     end poTVIP;
 118    --  ]
 119    --  po : poT;
 120    --  poTVIP (poTV!(po));
 121
 122    --  function poPT__B2s (O : address; E : protected_entry_index) return
 123    --    boolean is
 124    --     type poTVP is access poTV;
 125    --     _object : poTVP := poTVP!(O);
 126    --     poR : protection_entry renames _object._object;
 127    --     openP : boolean renames _object.open;
 128    --  begin
 129    --     return open;
 130    --  end poPT__B2s;
 131
 132    --  procedure poPT__E1s (O : address; P : address; E :
 133    --    protected_entry_index) is
 134    --     type poTVP is access poTV;
 135    --     _object : poTVP := poTVP!(O);
 136    --  begin
 137    --     B1b : declare
 138    --        poR : protection_entry renames _object._object;
 139    --        openP : boolean renames _object.open;
 140    --        ...variable declarations...
 141    --     begin
 142    --        ...B...
 143    --     end B1b;
 144    --     complete_single_entry_body (_object._object'unchecked_access);
 145    --     return;
 146    --  exception
 147    --     when all others =>
 148    --        exceptional_complete_single_entry_body (_object._object'
 149    --          unchecked_access, get_gnat_exception);
 150    --        return;
 151    --  end poPT__E1s;
 152
 153    --  procedure poPT__pN (_object : in out poTV) is
 154    --     poR : protection_entry renames _object._object;
 155    --     openP : boolean renames _object.open;
 156    --     ...variable declarations...
 157    --  begin
 158    --     ...C...
 159    --     return;
 160    --  end poPT__pN;
 161
 162    --  procedure poPT__pP (_object : in out poTV) is
 163    --     procedure _clean is
 164    --     begin
 165    --        service_entry (_object._object'unchecked_access);
 166    --        return;
 167    --     end _clean;
 168    --  begin
 169    --     lock_entry (_object._object'unchecked_access);
 170    --     B5b : begin
 171    --        poPT__pN (_object);
 172    --     at end
 173    --        _clean;
 174    --     end B5b;
 175    --     return;
 176    --  end poPT__pP;
 177
 178    type Protection_Entry is limited private;
 179    --  This type contains the GNARL state of a protected object. The
 180    --  application-defined portion of the state (i.e. private objects)
 181    --  is maintained by the compiler-generated code.
 182
 183    type Protection_Entry_Access is access all Protection_Entry;
 184
 185    type Entry_Body_Access is access constant Entry_Body;
 186    --  Access to barrier and action function of an entry
 187
 188    procedure Initialize_Protection_Entry
 189      (Object           : Protection_Entry_Access;
 190       Ceiling_Priority : Integer;
 191       Compiler_Info    : System.Address;
 192       Entry_Body       : Entry_Body_Access);
 193    --  Initialize the Object parameter so that it can be used by the run time
 194    --  to keep track of the runtime state of a protected object.
 195
 196    procedure Lock_Entry (Object : Protection_Entry_Access);
 197    --  Lock a protected object for write access. Upon return, the caller owns
 198    --  the lock to this object, and no other call to Lock or Lock_Read_Only
 199    --  with the same argument will return until the corresponding call to
 200    --  Unlock has been made by the caller.
 201
 202    procedure Lock_Read_Only_Entry
 203      (Object : Protection_Entry_Access);
 204    --  Lock a protected object for read access. Upon return, the caller owns
 205    --  the lock for read access, and no other calls to Lock with the same
 206    --  argument will return until the corresponding call to Unlock has been
 207    --  made by the caller. Other calls to Lock_Read_Only may (but need not)
 208    --  return before the call to Unlock, and the corresponding callers will
 209    --  also own the lock for read access.
 210
 211    procedure Unlock_Entry (Object : Protection_Entry_Access);
 212    --  Relinquish ownership of the lock for the object represented by the
 213    --  Object parameter. If this ownership was for write access, or if it was
 214    --  for read access where there are no other read access locks outstanding,
 215    --  one (or more, in the case of Lock_Read_Only) of the tasks waiting on
 216    --  this lock (if any) will be given the lock and allowed to return from
 217    --  the Lock or Lock_Read_Only call.
 218
 219    procedure Service_Entry (Object : Protection_Entry_Access);
 220    --  Service the entry queue of the specified object, executing the
 221    --  corresponding body of any queued entry call that is waiting on True
 222    --  barrier. This is used when the state of a protected object may have
 223    --  changed, in particular after the execution of the statement sequence
 224    --  of a protected procedure.
 225    --
 226    --  This must be called with abort deferred and with the corresponding
 227    --  object locked. Object is unlocked on return.
 228
 229    procedure Protected_Single_Entry_Call
 230      (Object              : Protection_Entry_Access;
 231       Uninterpreted_Data  : System.Address);
 232    --  Make a protected entry call to the specified object
 233    --
 234    --  Pends a protected entry call on the protected object represented by
 235    --  Object. A pended call is not queued; it may be executed immediately
 236    --  or queued, depending on the state of the entry barrier.
 237    --
 238    --    Uninterpreted_Data
 239    --      This will be returned by Next_Entry_Call when this call is serviced.
 240    --      It can be used by the compiler to pass information between the
 241    --      caller and the server, in particular entry parameters.
 242
 243    procedure Exceptional_Complete_Single_Entry_Body
 244      (Object : Protection_Entry_Access;
 245       Ex     : Ada.Exceptions.Exception_Id);
 246    --  Perform all of the functions of Complete_Entry_Body. In addition, report
 247    --  in Ex the exception whose propagation terminated the entry body to the
 248    --  runtime system.
 249
 250    function Protected_Count_Entry (Object : Protection_Entry) return Natural;
 251    --  Return the number of entry calls on Object (0 or 1)
 252
 253    function Protected_Single_Entry_Caller
 254      (Object : Protection_Entry) return Task_Id;
 255    --  Return value of E'Caller, where E is the protected entry currently being
 256    --  handled. This will only work if called from within an entry body, as
 257    --  required by the LRM (C.7.1(14)).
 258
 259 private
 260    type Protection_Entry is record
 261       Common : aliased Protection;
 262       --  State of the protected object. This part is common to any protected
 263       --  object, including those without entries.
 264
 265       Compiler_Info : System.Address;
 266       --  Pointer to compiler-generated record representing protected object
 267
 268       Call_In_Progress : Entry_Call_Link;
 269       --  Pointer to the entry call being executed (if any)
 270
 271       Entry_Body : Entry_Body_Access;
 272       --  Pointer to executable code for the entry body of the protected type
 273
 274       Entry_Queue : Entry_Call_Link;
 275       --  Place to store the waiting entry call (if any)
 276    end record;
 277
 278 end System.Tasking.Protected_Objects.Single_Entry;