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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 . S T A G E 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 -- This package represents the high level tasking interface used by the
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33 -- compiler to expand Ada 95 tasking constructs into simpler run time calls
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34 -- (aka GNARLI, GNU Ada Run-time Library Interface)
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35
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36 -- Note: Only the compiler is allowed to use this interface, by generating
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37 -- direct calls to it, via Rtsfind.
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38
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39 -- Any changes to this interface may require corresponding compiler changes
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40 -- in exp_ch9.adb and possibly exp_ch7.adb
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41
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42 with System.Task_Info;
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43 with System.Parameters;
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44
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45 with Ada.Real_Time;
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46
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47 package System.Tasking.Stages is
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48 pragma Elaborate_Body;
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49
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50 -- The compiler will expand in the GNAT tree the following construct:
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51
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52 -- task type T (Discr : Integer);
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53
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54 -- task body T is
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55 -- ...declarations, possibly some controlled...
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56 -- begin
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57 -- ...B...;
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58 -- end T;
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59
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60 -- T1 : T (1);
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61
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62 -- as follows:
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63
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64 -- enter_master.all;
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65
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66 -- _chain : aliased activation_chain;
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67 -- activation_chainIP (_chain);
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68
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69 -- task type t (discr : integer);
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70 -- tE : aliased boolean := false;
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71 -- tZ : size_type := unspecified_size;
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72 -- type tV (discr : integer) is limited record
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73 -- _task_id : task_id;
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74 -- end record;
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75 -- procedure tB (_task : access tV);
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76 -- freeze tV [
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77 -- procedure tVIP (_init : in out tV; _master : master_id;
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78 -- _chain : in out activation_chain; _task_id : in task_image_type;
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79 -- discr : integer) is
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80 -- begin
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81 -- _init.discr := discr;
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82 -- _init._task_id := null;
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83 -- create_task (unspecified_priority, tZ,
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84 -- unspecified_task_info, unspecified_cpu,
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85 -- ada__real_time__time_span_zero, 0, _master,
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86 -- task_procedure_access!(tB'address), _init'address,
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87 -- tE'unchecked_access, _chain, _task_id, _init._task_id);
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88 -- return;
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89 -- end tVIP;
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90 -- ]
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91
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92 -- procedure tB (_task : access tV) is
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93 -- discr : integer renames _task.discr;
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94
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95 -- procedure _clean is
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96 -- begin
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97 -- abort_defer.all;
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98 -- complete_task;
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99 -- finalize_list (F14b);
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100 -- abort_undefer.all;
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101 -- return;
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102 -- end _clean;
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103 -- begin
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104 -- abort_undefer.all;
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105 -- ...declarations...
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106 -- complete_activation;
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107 -- ...B...;
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108 -- return;
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109 -- at end
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110 -- _clean;
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111 -- end tB;
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112
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113 -- tE := true;
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114 -- t1 : t (1);
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115 -- _master : constant master_id := current_master.all;
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116 -- t1S : task_image_type := new string'"t1";
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117 -- task_image_typeIP (t1, _master, _chain, t1S, 1);
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118
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119 -- activate_tasks (_chain'unchecked_access);
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120
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121 procedure Abort_Tasks (Tasks : Task_List);
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122 -- Compiler interface only. Do not call from within the RTS. Initiate
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123 -- abort, however, the actual abort is done by abortee by means of
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124 -- Abort_Handler and Abort_Undefer
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125 --
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126 -- source code:
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127 -- Abort T1, T2;
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128 -- code expansion:
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129 -- abort_tasks (task_list'(t1._task_id, t2._task_id));
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130
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131 procedure Activate_Tasks (Chain_Access : Activation_Chain_Access);
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132 -- Compiler interface only. Do not call from within the RTS.
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133 -- This must be called by the creator of a chain of one or more new tasks,
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134 -- to activate them. The chain is a linked list that up to this point is
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135 -- only known to the task that created them, though the individual tasks
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136 -- are already in the All_Tasks_List.
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137 --
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138 -- The compiler builds the chain in LIFO order (as a stack). Another
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139 -- version of this procedure had code to reverse the chain, so as to
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140 -- activate the tasks in the order of declaration. This might be nice, but
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141 -- it is not needed if priority-based scheduling is supported, since all
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142 -- the activated tasks synchronize on the activators lock before they
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143 -- start activating and so they should start activating in priority order.
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144 -- ??? Actually, the body of this package DOES reverse the chain, so I
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145 -- don't understand the above comment.
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146
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147 procedure Complete_Activation;
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148 -- Compiler interface only. Do not call from within the RTS.
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149 -- This should be called from the task body at the end of
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150 -- the elaboration code for its declarative part.
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151 -- Decrement the count of tasks to be activated by the activator and
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152 -- wake it up so it can check to see if all tasks have been activated.
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153 -- Except for the environment task, which should never call this procedure,
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154 -- T.Activator should only be null iff T has completed activation.
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155
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156 procedure Complete_Master;
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157 -- Compiler interface only. Do not call from within the RTS. This must
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158 -- be called on exit from any master where Enter_Master was called.
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159 -- Assume abort is deferred at this point.
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160
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161 procedure Complete_Task;
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162 -- Compiler interface only. Do not call from within the RTS.
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163 -- This should be called from an implicit at-end handler
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164 -- associated with the task body, when it completes.
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165 -- From this point, the current task will become not callable.
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166 -- If the current task have not completed activation, this should be done
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167 -- now in order to wake up the activator (the environment task).
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168
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169 procedure Create_Task
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170 (Priority : Integer;
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171 Stack_Size : System.Parameters.Size_Type;
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172 Secondary_Stack_Size : System.Parameters.Size_Type;
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173 Task_Info : System.Task_Info.Task_Info_Type;
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174 CPU : Integer;
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175 Relative_Deadline : Ada.Real_Time.Time_Span;
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176 Domain : Dispatching_Domain_Access;
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177 Num_Entries : Task_Entry_Index;
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178 Master : Master_Level;
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179 State : Task_Procedure_Access;
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180 Discriminants : System.Address;
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181 Elaborated : Access_Boolean;
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182 Chain : in out Activation_Chain;
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183 Task_Image : String;
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184 Created_Task : out Task_Id);
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185 -- Compiler interface only. Do not call from within the RTS.
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186 -- This must be called to create a new task.
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187 --
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188 -- Priority is the task's priority (assumed to be in range of type
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189 -- System.Any_Priority)
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190 --
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191 -- Stack_Size is the stack size of the task to create
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192 --
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193 -- Secondary_Stack_Size is the size of the secondary stack to be used by
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194 -- the task.
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195 --
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196 -- Task_Info is the task info associated with the created task, or
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197 -- Unspecified_Task_Info if none.
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198 --
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199 -- CPU is the task affinity. Passed as an Integer because the undefined
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200 -- value is not in the range of CPU_Range. Static range checks are
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201 -- performed when analyzing the pragma, and dynamic ones are performed
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202 -- before setting the affinity at run time.
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203 --
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204 -- Relative_Deadline is the relative deadline associated with the created
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205 -- task by means of a pragma Relative_Deadline, or 0.0 if none.
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206 --
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207 -- Domain is the dispatching domain associated with the created task by
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208 -- means of a Dispatching_Domain pragma or aspect, or null if none.
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209 --
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210 -- State is the compiler generated task's procedure body
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211 --
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212 -- Discriminants is a pointer to a limited record whose discriminants
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213 -- are those of the task to create. This parameter should be passed as
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214 -- the single argument to State.
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215 --
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216 -- Elaborated is a pointer to a Boolean that must be set to true on exit
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217 -- if the task could be successfully elaborated.
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218 --
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219 -- Chain is a linked list of task that needs to be created. On exit,
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220 -- Created_Task.Activation_Link will be Chain.T_ID, and Chain.T_ID
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221 -- will be Created_Task (e.g the created task will be linked at the front
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222 -- of Chain).
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223 --
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224 -- Task_Image is a string created by the compiler that the
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225 -- run time can store to ease the debugging and the
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226 -- Ada.Task_Identification facility.
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227 --
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228 -- Created_Task is the resulting task.
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229 --
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230 -- This procedure can raise Storage_Error if the task creation failed.
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231
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232 function Current_Master return Master_Level;
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233 -- Compiler interface only.
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234 -- This is called to obtain the current master nesting level.
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235
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236 procedure Enter_Master;
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237 -- Compiler interface only. Do not call from within the RTS.
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238 -- This must be called on entry to any "master" where a task,
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239 -- or access type designating objects containing tasks, may be
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240 -- declared.
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241
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242 procedure Expunge_Unactivated_Tasks (Chain : in out Activation_Chain);
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243 -- Compiler interface only. Do not call from within the RTS.
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244 -- This must be called by the compiler-generated code for an allocator if
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245 -- the allocated object contains tasks, if the allocator exits without
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246 -- calling Activate_Tasks for a given activation chains, as can happen if
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247 -- an exception occurs during initialization of the object.
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248 --
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249 -- This should be called ONLY for tasks created via an allocator. Recovery
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250 -- of storage for unactivated local task declarations is done by
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251 -- Complete_Master and Complete_Task.
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252 --
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253 -- We remove each task from Chain and All_Tasks_List before we free the
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254 -- storage of its ATCB.
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255 --
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256 -- In other places where we recover the storage of unactivated tasks, we
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257 -- need to clean out the entry queues, but here that should not be
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258 -- necessary, since these tasks should not have been visible to any other
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259 -- tasks, and so no task should be able to queue a call on their entries.
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260 --
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261 -- Just in case somebody misuses this subprogram, there is a check to
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262 -- verify this condition.
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263
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264 procedure Finalize_Global_Tasks;
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265 -- This should be called to complete the execution of the environment task
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266 -- and shut down the tasking runtime system. It is the equivalent of
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267 -- Complete_Task, but for the environment task.
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268 --
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269 -- The environment task must first call Complete_Master, to wait for user
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270 -- tasks that depend on library-level packages to terminate. It then calls
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271 -- Abort_Dependents to abort the "independent" library-level server tasks
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272 -- that are created implicitly by the RTS packages (signal and timer server
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273 -- tasks), and then waits for them to terminate. Then, it calls
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274 -- Vulnerable_Complete_Task.
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275 --
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276 -- It currently also executes the global finalization list, and then resets
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277 -- the "soft links".
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278
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279 procedure Free_Task (T : Task_Id);
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280 -- Recover all runtime system storage associated with the task T, but only
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281 -- if T has terminated. Do nothing in the other case. It is called from
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282 -- Unchecked_Deallocation, for objects that are or contain tasks.
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283
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284 procedure Move_Activation_Chain
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285 (From, To : Activation_Chain_Access;
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286 New_Master : Master_ID);
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287 -- Compiler interface only. Do not call from within the RTS.
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131
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288 -- Move all tasks on From list to To list, and change their Master_Of_Task
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289 -- to be New_Master. This is used to implement build-in-place function
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290 -- returns. Tasks that are part of the return object are initially placed
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291 -- on an activation chain local to the return statement, and their master
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292 -- is the return statement, in case the return statement is left
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293 -- prematurely (due to raising an exception, being aborted, or a goto or
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294 -- exit statement). Once the return statement has completed successfully,
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295 -- Move_Activation_Chain is called to move them to the caller's activation
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296 -- chain, and change their master to the one passed in by the caller. If
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297 -- that doesn't happen, they will never be activated, and will become
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298 -- terminated on leaving the return statement.
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299
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300 function Terminated (T : Task_Id) return Boolean;
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301 -- This is called by the compiler to implement the 'Terminated attribute.
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302 -- Though is not required to be so by the ARM, we choose to synchronize
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303 -- with the task's ATCB, so that this is more useful for polling the state
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304 -- of a task, and so that it becomes an abort completion point for the
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305 -- calling task (via Undefer_Abort).
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306 --
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307 -- source code:
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308 -- T1'Terminated
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309 --
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310 -- code expansion:
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311 -- terminated (t1._task_id)
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312
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313 procedure Terminate_Task (Self_ID : Task_Id);
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314 -- Terminate the calling task.
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315 -- This should only be called by the Task_Wrapper procedure, and to
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316 -- deallocate storage associate with foreign tasks.
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317
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318 end System.Tasking.Stages;
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