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1 ------------------------------------------------------------------------------
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2 -- --
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3 -- GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS --
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4 -- --
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5 -- S Y S T E M . T A S K I N G . R E N D E Z V O U S --
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6 -- --
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7 -- S p e c --
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8 -- --
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131
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9 -- Copyright (C) 1992-2018, Free Software Foundation, Inc. --
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111
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10 -- --
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11 -- GNARL is free software; you can redistribute it and/or modify it under --
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12 -- terms of the GNU General Public License as published by the Free Soft- --
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13 -- ware Foundation; either version 3, or (at your option) any later ver- --
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14 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
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15 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
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16 -- or FITNESS FOR A PARTICULAR PURPOSE. --
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17 -- --
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18 -- As a special exception under Section 7 of GPL version 3, you are granted --
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19 -- additional permissions described in the GCC Runtime Library Exception, --
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20 -- version 3.1, as published by the Free Software Foundation. --
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21 -- --
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22 -- You should have received a copy of the GNU General Public License and --
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23 -- a copy of the GCC Runtime Library Exception along with this program; --
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24 -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
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25 -- <http://www.gnu.org/licenses/>. --
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26 -- --
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27 -- GNARL was developed by the GNARL team at Florida State University. --
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28 -- Extensive contributions were provided by Ada Core Technologies, Inc. --
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29 -- --
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30 ------------------------------------------------------------------------------
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31
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32 -- Note: the compiler generates direct calls to this interface, via Rtsfind.
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33 -- Any changes to this interface may require corresponding compiler changes.
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34
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35 with Ada.Exceptions;
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36
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37 with System.Tasking.Protected_Objects.Entries;
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38
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39 package System.Tasking.Rendezvous is
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40
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41 package STPE renames System.Tasking.Protected_Objects.Entries;
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42
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43 procedure Task_Entry_Call
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44 (Acceptor : Task_Id;
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45 E : Task_Entry_Index;
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46 Uninterpreted_Data : System.Address;
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47 Mode : Call_Modes;
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48 Rendezvous_Successful : out Boolean);
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49 -- General entry call used to implement ATC or conditional entry calls.
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50 -- Compiler interface only. Do not call from within the RTS.
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51 -- Acceptor is the ID of the acceptor task.
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52 -- E is the entry index requested.
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53 -- Uninterpreted_Data represents the parameters of the entry. It is
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54 -- constructed by the compiler for the caller and the callee; therefore,
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55 -- the run time never needs to decode this data.
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56 -- Mode can be either Asynchronous_Call (ATC) or Conditional_Call.
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57 -- Rendezvous_Successful is set to True on return if the call was serviced.
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58
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59 procedure Timed_Task_Entry_Call
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60 (Acceptor : Task_Id;
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61 E : Task_Entry_Index;
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62 Uninterpreted_Data : System.Address;
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63 Timeout : Duration;
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64 Mode : Delay_Modes;
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65 Rendezvous_Successful : out Boolean);
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66 -- Timed entry call without using ATC.
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67 -- Compiler interface only. Do not call from within the RTS.
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68 -- See Task_Entry_Call for details on Acceptor, E and Uninterpreted_Data.
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69 -- Timeout is the value of the time out.
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70 -- Mode determines whether the delay is relative or absolute.
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71
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72 procedure Call_Simple
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73 (Acceptor : Task_Id;
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74 E : Task_Entry_Index;
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75 Uninterpreted_Data : System.Address);
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76 -- Simple entry call.
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77 -- Compiler interface only. Do not call from within the RTS.
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78 --
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79 -- source:
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80 -- T.E1 (Params);
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81 --
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82 -- expansion:
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83 -- declare
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84 -- P : parms := (parm1, parm2, parm3);
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85 -- X : Task_Entry_Index := 1;
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86 -- begin
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87 -- Call_Simple (t._task_id, X, P'Address);
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88 -- parm1 := P.param1;
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89 -- parm2 := P.param2;
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90 -- ...
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91 -- end;
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92
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93 procedure Cancel_Task_Entry_Call (Cancelled : out Boolean);
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94 -- Cancel pending asynchronous task entry call.
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95 -- Compiler interface only. Do not call from within the RTS.
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96 -- See Exp_Ch9.Expand_N_Asynchronous_Select for code expansion.
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97
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98 procedure Requeue_Task_Entry
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99 (Acceptor : Task_Id;
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100 E : Task_Entry_Index;
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101 With_Abort : Boolean);
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102 -- Requeue from a task entry to a task entry.
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103 -- Compiler interface only. Do not call from within the RTS.
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104 -- The code generation for task entry requeues is different from that for
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105 -- protected entry requeues. There is a "goto" that skips around the call
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106 -- to Complete_Rendezvous, so that Requeue_Task_Entry must also do the work
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107 -- of Complete_Rendezvous. The difference is that it does not report that
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108 -- the call's State = Done.
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109 --
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110 -- source:
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111 -- accept e1 do
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112 -- ...A...
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113 -- requeue e2;
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114 -- ...B...
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115 -- end e1;
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116 --
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117 -- expansion:
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118 -- A62b : address;
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119 -- L61b : label
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120 -- begin
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121 -- accept_call (1, A62b);
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122 -- ...A...
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123 -- requeue_task_entry (tTV!(t)._task_id, 2, false);
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124 -- goto L61b;
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125 -- ...B...
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126 -- complete_rendezvous;
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127 -- <<L61b>>
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128 -- exception
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129 -- when others =>
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130 -- exceptional_complete_rendezvous (current_exception);
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131 -- end;
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132
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133 procedure Requeue_Protected_To_Task_Entry
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134 (Object : STPE.Protection_Entries_Access;
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135 Acceptor : Task_Id;
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136 E : Task_Entry_Index;
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137 With_Abort : Boolean);
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138 -- Requeue from a protected entry to a task entry.
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139 -- Compiler interface only. Do not call from within the RTS.
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140 --
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141 -- source:
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142 -- entry e2 when b is
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143 -- begin
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144 -- b := false;
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145 -- ...A...
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146 -- requeue t.e2;
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147 -- end e2;
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148 --
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149 -- expansion:
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150 -- procedure rPT__E14b (O : address; P : address; E :
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151 -- protected_entry_index) is
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152 -- type rTVP is access rTV;
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153 -- freeze rTVP []
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154 -- _object : rTVP := rTVP!(O);
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155 -- begin
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156 -- declare
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157 -- rR : protection renames _object._object;
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158 -- vP : integer renames _object.v;
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159 -- bP : boolean renames _object.b;
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160 -- begin
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161 -- b := false;
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162 -- ...A...
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163 -- requeue_protected_to_task_entry (rR'unchecked_access, tTV!(t).
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164 -- _task_id, 2, false);
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165 -- return;
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166 -- end;
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167 -- complete_entry_body (_object._object'unchecked_access, objectF =>
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168 -- 0);
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169 -- return;
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170 -- exception
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171 -- when others =>
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172 -- abort_undefer.all;
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173 -- exceptional_complete_entry_body (_object._object'
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174 -- unchecked_access, current_exception, objectF => 0);
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175 -- return;
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176 -- end rPT__E14b;
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177
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178 procedure Selective_Wait
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179 (Open_Accepts : Accept_List_Access;
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180 Select_Mode : Select_Modes;
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181 Uninterpreted_Data : out System.Address;
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182 Index : out Select_Index);
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183 -- Implement select statement.
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184 -- Compiler interface only. Do not call from within the RTS.
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185 -- See comments on Accept_Call.
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186 --
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187 -- source:
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188 -- select accept e1 do
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189 -- ...A...
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190 -- end e1;
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191 -- ...B...
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192 -- or accept e2;
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193 -- ...C...
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194 -- end select;
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195 --
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196 -- expansion:
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197 -- A32b : address;
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198 -- declare
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199 -- A37b : T36b;
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200 -- A37b (1) := (null_body => false, s => 1);
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201 -- A37b (2) := (null_body => true, s => 2);
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202 -- S0 : aliased T36b := accept_list'A37b;
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203 -- J1 : select_index := 0;
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204 -- procedure e1A is
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205 -- begin
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206 -- abort_undefer.all;
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207 -- ...A...
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208 -- <<L31b>>
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209 -- complete_rendezvous;
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210 -- exception
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211 -- when all others =>
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212 -- exceptional_complete_rendezvous (get_gnat_exception);
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213 -- end e1A;
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214 -- begin
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215 -- selective_wait (S0'unchecked_access, simple_mode, A32b, J1);
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216 -- case J1 is
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217 -- when 0 =>
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218 -- goto L3;
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219 -- when 1 =>
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220 -- e1A;
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221 -- goto L1;
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222 -- when 2 =>
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223 -- goto L2;
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224 -- when others =>
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225 -- goto L3;
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226 -- end case;
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227 -- <<L1>>
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228 -- ...B...
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229 -- goto L3;
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230 -- <<L2>>
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231 -- ...C...
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232 -- goto L3;
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233 -- <<L3>>
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234 -- end;
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235
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236 procedure Timed_Selective_Wait
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237 (Open_Accepts : Accept_List_Access;
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238 Select_Mode : Select_Modes;
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239 Uninterpreted_Data : out System.Address;
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240 Timeout : Duration;
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241 Mode : Delay_Modes;
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242 Index : out Select_Index);
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243 -- Selective wait with timeout without using ATC.
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244 -- Compiler interface only. Do not call from within the RTS.
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245
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246 procedure Accept_Call
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247 (E : Task_Entry_Index;
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248 Uninterpreted_Data : out System.Address);
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249 -- Accept an entry call.
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250 -- Compiler interface only. Do not call from within the RTS.
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251 --
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252 -- source:
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253 -- accept E do ...A... end E;
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254 -- expansion:
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255 -- A27b : address;
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256 -- L26b : label
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257 -- begin
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258 -- accept_call (1, A27b);
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259 -- ...A...
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260 -- complete_rendezvous;
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261 -- <<L26b>>
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262 -- exception
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263 -- when all others =>
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264 -- exceptional_complete_rendezvous (get_gnat_exception);
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265 -- end;
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266 --
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267 -- The handler for Abort_Signal (*all* others) is to handle the case when
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268 -- the acceptor is aborted between Accept_Call and the corresponding
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269 -- Complete_Rendezvous call. We need to wake up the caller in this case.
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270 --
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271 -- See also Selective_Wait
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272
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273 procedure Accept_Trivial (E : Task_Entry_Index);
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274 -- Accept an entry call that has no parameters and no body.
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275 -- Compiler interface only. Do not call from within the RTS.
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276 -- This should only be called when there is no accept body, or the accept
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277 -- body is empty.
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278 --
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279 -- source:
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280 -- accept E;
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281 -- expansion:
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282 -- accept_trivial (1);
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283 --
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284 -- The compiler is also able to recognize the following and
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285 -- translate it the same way.
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286 --
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287 -- accept E do null; end E;
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288
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289 function Task_Count (E : Task_Entry_Index) return Natural;
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290 -- Return number of tasks waiting on the entry E (of current task)
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291 -- Compiler interface only. Do not call from within the RTS.
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292
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293 function Callable (T : Task_Id) return Boolean;
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294 -- Return T'Callable
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295 -- Compiler interface. Do not call from within the RTS, except for body of
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296 -- Ada.Task_Identification.
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297
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298 type Task_Entry_Nesting_Depth is new Task_Entry_Index
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299 range 0 .. Max_Task_Entry;
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300
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301 function Task_Entry_Caller (D : Task_Entry_Nesting_Depth) return Task_Id;
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302 -- Return E'Caller. This will only work if called from within an
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303 -- accept statement that is handling E, as required by the LRM (C.7.1(14)).
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304 -- Compiler interface only. Do not call from within the RTS.
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305
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306 procedure Complete_Rendezvous;
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307 -- Called by acceptor to wake up caller
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308
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309 procedure Exceptional_Complete_Rendezvous
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310 (Ex : Ada.Exceptions.Exception_Id);
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311 pragma No_Return (Exceptional_Complete_Rendezvous);
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312 -- Called by acceptor to mark the end of the current rendezvous and
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313 -- propagate an exception to the caller.
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314
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315 -- For internal use only:
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316
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317 function Task_Do_Or_Queue
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318 (Self_ID : Task_Id;
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319 Entry_Call : Entry_Call_Link) return Boolean;
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320 -- Call this only with abort deferred and holding no locks, except
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321 -- the global RTS lock when Single_Lock is True which must be owned.
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322 -- Returns False iff the call cannot be served or queued, as is the
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323 -- case if the caller is not callable; i.e., a False return value
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324 -- indicates that Tasking_Error should be raised.
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325 -- Either initiate the entry call, such that the accepting task is
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326 -- free to execute the rendezvous, queue the call on the acceptor's
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327 -- queue, or cancel the call. Conditional calls that cannot be
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328 -- accepted immediately are cancelled.
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329
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330 end System.Tasking.Rendezvous;
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