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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 . I N I T I A L I Z A T I O N --
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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 provides overall initialization of the tasking portion of the
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33 -- RTS. This package must be elaborated before any tasking features are used.
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34
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35 package System.Tasking.Initialization is
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36
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37 procedure Remove_From_All_Tasks_List (T : Task_Id);
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38 -- Remove T from All_Tasks_List. Call this function with RTS_Lock taken
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39
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40 procedure Finalize_Attributes (T : Task_Id);
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41 -- Finalize all attributes from T. This is to be called just before the
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42 -- ATCB is deallocated. It relies on the caller holding T.L write-lock
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43 -- on entry.
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44
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45 ---------------------------------
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46 -- Tasking-Specific Soft Links --
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47 ---------------------------------
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48
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49 -------------------------
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50 -- Abort Defer/Undefer --
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51 -------------------------
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52
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53 -- Defer_Abort defers the effects of low-level abort and priority change
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54 -- in the calling task until a matching Undefer_Abort call is executed.
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55
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56 -- Undefer_Abort DOES MORE than just undo the effects of one call to
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57 -- Defer_Abort. It is the universal "polling point" for deferred
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58 -- processing, including the following:
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59
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60 -- 1) base priority changes
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61
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62 -- 2) abort/ATC
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63
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64 -- Abort deferral MAY be nested (Self_ID.Deferral_Level is a count), but
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65 -- to avoid waste and undetected errors, it generally SHOULD NOT be
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66 -- nested. The symptom of over-deferring abort is that an exception may
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67 -- fail to be raised, or an abort may fail to take place.
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68
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69 -- Therefore, there are two sets of the inlineable defer/undefer routines,
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70 -- which are the ones to be used inside GNARL. One set allows nesting. The
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71 -- other does not. People who maintain the GNARL should try to avoid using
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72 -- the nested versions, or at least look very critically at the places
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73 -- where they are used.
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74
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75 -- In general, any GNARL call that is potentially blocking, or whose
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76 -- semantics require that it sometimes raise an exception, or that is
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77 -- required to be an abort completion point, must be made with abort
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78 -- Deferral_Level = 1.
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79
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80 -- In general, non-blocking GNARL calls, which may be made from inside a
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81 -- protected action, are likely to need to allow nested abort deferral.
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82
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83 -- With some critical exceptions (which are supposed to be documented),
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84 -- internal calls to the tasking runtime system assume abort is already
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85 -- deferred, and do not modify the deferral level.
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86
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87 -- There is also a set of non-inlineable defer/undefer routines, for direct
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88 -- call from the compiler. These are not inlineable because they may need
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89 -- to be called via pointers ("soft links"). For the sake of efficiency,
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90 -- the version with Self_ID as parameter should used wherever possible.
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91 -- These are all nestable.
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92
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93 -- Non-nestable inline versions
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94
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95 procedure Defer_Abort (Self_ID : Task_Id);
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96 pragma Inline (Defer_Abort);
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97
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98 procedure Undefer_Abort (Self_ID : Task_Id);
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99 pragma Inline (Undefer_Abort);
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100
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101 -- Nestable inline versions
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102
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103 procedure Defer_Abort_Nestable (Self_ID : Task_Id);
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104 pragma Inline (Defer_Abort_Nestable);
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105
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106 procedure Undefer_Abort_Nestable (Self_ID : Task_Id);
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107 pragma Inline (Undefer_Abort_Nestable);
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108
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109 procedure Do_Pending_Action (Self_ID : Task_Id);
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110 -- Only call with no locks, and when Self_ID.Pending_Action = True Perform
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111 -- necessary pending actions (e.g. abort, priority change). This procedure
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112 -- is usually called when needed as a result of calling Undefer_Abort,
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113 -- although in the case of e.g. No_Abort restriction, it can be necessary
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114 -- to force execution of pending actions.
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115
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116 function Check_Abort_Status return Integer;
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117 -- Returns Boolean'Pos (True) iff abort signal should raise
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118 -- Standard'Abort_Signal. Only used by IRIX currently.
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119
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120 --------------------------
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121 -- Change Base Priority --
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122 --------------------------
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123
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124 procedure Change_Base_Priority (T : Task_Id);
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125 -- Change the base priority of T. Has to be called with the affected
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126 -- task's ATCB write-locked. May temporarily release the lock.
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127
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128 ----------------------
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129 -- Task Lock/Unlock --
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130 ----------------------
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131
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132 procedure Task_Lock (Self_ID : Task_Id);
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133 pragma Inline (Task_Lock);
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134
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135 procedure Task_Unlock (Self_ID : Task_Id);
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136 pragma Inline (Task_Unlock);
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137 -- These are versions of Lock_Task and Unlock_Task created for use
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138 -- within the GNARL.
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139
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140 procedure Final_Task_Unlock (Self_ID : Task_Id);
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141 -- This version is only for use in Terminate_Task, when the task is
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142 -- relinquishing further rights to its own ATCB. There is a very
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143 -- interesting potential race condition there, where the old task may run
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144 -- concurrently with a new task that is allocated the old tasks (now
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145 -- reused) ATCB. The critical thing here is to not make any reference to
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146 -- the ATCB after the lock is released. See also comments on
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147 -- Terminate_Task and Unlock.
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148
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149 procedure Wakeup_Entry_Caller
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150 (Self_ID : Task_Id;
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151 Entry_Call : Entry_Call_Link;
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152 New_State : Entry_Call_State);
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153 pragma Inline (Wakeup_Entry_Caller);
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154 -- This is called at the end of service of an entry call, to abort the
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155 -- caller if he is in an abortable part, and to wake up the caller if he
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156 -- is on Entry_Caller_Sleep. Call it holding the lock of Entry_Call.Self.
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157 --
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158 -- Timed_Call or Simple_Call:
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159 -- The caller is waiting on Entry_Caller_Sleep, in Wait_For_Completion,
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160 -- or Wait_For_Completion_With_Timeout.
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161 --
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162 -- Conditional_Call:
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163 -- The caller might be in Wait_For_Completion,
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164 -- waiting for a rendezvous (possibly requeued without abort) to
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165 -- complete.
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166 --
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167 -- Asynchronous_Call:
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168 -- The caller may be executing in the abortable part an async. select,
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169 -- or on a time delay, if Entry_Call.State >= Was_Abortable.
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170
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171 procedure Locked_Abort_To_Level
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172 (Self_ID : Task_Id;
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173 T : Task_Id;
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174 L : ATC_Level);
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175 pragma Inline (Locked_Abort_To_Level);
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176 -- Abort a task to a specified ATC level. Call this only with T locked
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177
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178 end System.Tasking.Initialization;
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