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1 -- C954001.A
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2 --
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3 -- Grant of Unlimited Rights
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4 --
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5 -- Under contracts F33600-87-D-0337, F33600-84-D-0280, MDA903-79-C-0687,
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6 -- F08630-91-C-0015, and DCA100-97-D-0025, the U.S. Government obtained
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7 -- unlimited rights in the software and documentation contained herein.
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8 -- Unlimited rights are defined in DFAR 252.227-7013(a)(19). By making
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9 -- this public release, the Government intends to confer upon all
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10 -- recipients unlimited rights equal to those held by the Government.
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11 -- These rights include rights to use, duplicate, release or disclose the
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12 -- released technical data and computer software in whole or in part, in
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13 -- any manner and for any purpose whatsoever, and to have or permit others
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14 -- to do so.
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15 --
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16 -- DISCLAIMER
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17 --
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18 -- ALL MATERIALS OR INFORMATION HEREIN RELEASED, MADE AVAILABLE OR
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19 -- DISCLOSED ARE AS IS. THE GOVERNMENT MAKES NO EXPRESS OR IMPLIED
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20 -- WARRANTY AS TO ANY MATTER WHATSOEVER, INCLUDING THE CONDITIONS OF THE
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21 -- SOFTWARE, DOCUMENTATION OR OTHER INFORMATION RELEASED, MADE AVAILABLE
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22 -- OR DISCLOSED, OR THE OWNERSHIP, MERCHANTABILITY, OR FITNESS FOR A
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23 -- PARTICULAR PURPOSE OF SAID MATERIAL.
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24 --*
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25 --
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26 -- OBJECTIVE:
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27 -- Check that a requeue statement within an entry_body with parameters
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28 -- may requeue the entry call to a protected entry with a subtype-
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29 -- conformant parameter profile. Check that, if the call is queued on the
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30 -- new entry's queue, the original caller remains blocked after the
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31 -- requeue, but the entry_body containing the requeue is completed.
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32 --
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33 -- TEST DESCRIPTION:
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34 -- Declare a protected object which simulates a disk device. Declare an
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35 -- entry that requeues the caller to a second entry if the disk head is
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36 -- not in the proper location, but first sets the second entry's barrier
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37 -- to false. Declare a procedure which sets the second entry's barrier
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38 -- to true.
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39 --
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40 -- Declare a task which calls the first entry such that the requeue is
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41 -- called. This task should be queued on the second entry and remain
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42 -- blocked, and the first entry should be complete. Call the procedure
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43 -- which releases the second entry's queue. The second entry should
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44 -- complete, after which the task should complete.
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45 --
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46 --
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47 -- CHANGE HISTORY:
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48 -- 06 Dec 94 SAIC ACVC 2.0
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49 --
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50 --!
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51
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52 package C954001_0 is -- Disk management abstraction.
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53
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54
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55 -- Simulate a read-only disk device with a head that may be moved to
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56 -- different tracks. If a read request is issued for the current
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57 -- track, the request can be satisfied immediately. Otherwise, the head
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58 -- must be moved to the correct track, during which time the calling task
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59 -- is blocked. When the head reaches the correct track, the disk generates
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60 -- an interrupt, after which the request can be satisfied, and the
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61 -- calling task can proceed.
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62
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63 Buffer_Size : constant := 100;
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64
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65 type Disk_Buffer is new String (1 .. Buffer_Size);
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66 type Disk_Track is new Natural;
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67
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68 type Disk_Address is record
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69 Track : Disk_Track;
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70 -- Additional components.
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71 end record;
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72
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73 Initial_Track : constant Disk_Track := 0;
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74 New_Track : constant Disk_Track := 5;
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75
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76 --==============================================--
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77
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78 protected Disk_Device is
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79
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80 entry Read (Where : Disk_Address; -- Read data from disk
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81 Data : out Disk_Buffer); -- track.
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82
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83 procedure Disk_Interrupt; -- Handle interrupt
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84 -- from disk.
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85
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86 function TC_Track return Disk_Track; -- Return current track.
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87
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88 function TC_Pending_Queued return Boolean; -- True when there is
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89 -- an entry in queue
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90
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91 private
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92
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93 entry Pending_Read (Where : Disk_Address; -- Wait for head to
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94 Data : out Disk_Buffer); -- move then read data.
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95
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96 Current_Track : Disk_Track := Initial_Track; -- Current disk track.
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97 Operation_Pending : Boolean := False; -- Vis. entry barrier.
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98 Disk_Interrupted : Boolean := False; -- Priv. entry barrier.
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99
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100 end Disk_Device;
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101
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102
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103 end C954001_0;
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104
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105
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106 --==================================================================--
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107
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108
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109 package body C954001_0 is -- Disk management abstraction.
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110
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111
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112 protected body Disk_Device is
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113
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114 entry Read (Where : Disk_Address; Data : out Disk_Buffer)
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115 when not Operation_Pending is
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116 begin
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117 if (Where.Track = Current_Track) then -- If the head is over the
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118 -- Read data from disk... -- requested track, read
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119 null; -- the data.
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120
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121 else -- Otherwise, defer read
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122 Operation_Pending := True; -- while head is moved to
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123 -- correct track (signaled
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124 -- -- -- by a disk interrupt).
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125 -- Requeue is tested here --
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126 -- --
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127
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128 requeue Pending_Read;
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129
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130 end if;
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131 end Read;
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132
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133
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134 procedure Disk_Interrupt is -- Called when the disk
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135 begin -- interrupts, indicating
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136 Disk_Interrupted := True; -- that the head is over
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137 end Disk_Interrupt; -- the correct track.
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138
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139
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140 function TC_Track return Disk_Track is -- Artifice required for
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141 begin -- testing purposes.
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142 return (Current_Track);
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143 end TC_Track;
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144
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145
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146 entry Pending_Read (Where : Disk_Address; Data : out Disk_Buffer)
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147 when Disk_Interrupted is
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148 begin
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149 Current_Track := Where.Track; -- Head is now over the
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150 -- Read data from disk... -- correct track; read
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151 Operation_Pending := False; -- the data.
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152 Disk_Interrupted := False;
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153 end Pending_Read;
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154
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155 function TC_Pending_Queued return Boolean is
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156 begin
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157 -- Return true when there is something on the Pending_Read queue
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158 return (Pending_Read'Count /=0);
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159 end TC_Pending_Queued;
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160
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161 end Disk_Device;
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162
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163
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164 end C954001_0;
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165
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166
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167 --==================================================================--
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168
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169
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170 with Report;
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171 with ImpDef;
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172
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173 with C954001_0; -- Disk management abstraction.
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174 use C954001_0;
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175
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176 procedure C954001 is
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177
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178
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179 task type Read_Task is -- an unusual (but legal) declaration
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180 end Read_Task;
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181 --
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182 --
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183 task body Read_Task is
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184 Location : constant Disk_Address := (Track => New_Track);
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185 Data : Disk_Buffer := (others => ' ');
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186 begin
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187 Disk_Device.Read (Location, Data); -- Invoke requeue statement.
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188 exception
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189 when others =>
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190 Report.Failed ("Exception raised in task");
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191 end Read_Task;
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192
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193 --==============================================--
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194
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195 begin -- Main program.
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196
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197 Report.Test ("C954001", "Requeue from an entry within a P.O. " &
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198 "to a private entry within the same P.O.");
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199
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200
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201 declare
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202
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203 IO_Request : Read_Task; -- Request a read from other
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204 -- than the current track.
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205 -- IO_Request will be requeued
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206 -- from Read to Pending_Read.
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207 begin
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208
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209 -- To pass this test, the following must be true:
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210 --
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211 -- (A) The Read entry call made by the task IO_Request must be
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212 -- completed by the requeue.
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213 -- (B) IO_Request must remain blocked following the requeue.
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214 -- (C) IO_Request must be queued on the Pending_Read entry queue.
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215 -- (D) IO_Request must continue execution after the Pending_Read
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216 -- entry completes.
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217 --
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218 -- First, verify (A): that the Read entry call is complete.
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219 --
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220 -- Call a protected operation (Disk_Device.TC_Track). Since no two
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221 -- protected actions may proceed concurrently unless both are protected
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222 -- function calls, a call to a protected operation at this point can
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223 -- proceed only if the Read entry call is already complete.
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224 --
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225 -- Note that if Read is NOT complete, the test will likely hang here.
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226 --
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227 -- Next, verify (B): that IO_Request remains blocked following the
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228 -- requeue. Also verify that Pending_Read (the entry to which
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229 -- IO_Request should have been queued) has not yet executed.
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230
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231 -- Wait until the task had made the call and the requeue has been
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232 -- effected.
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233 while not Disk_Device.TC_Pending_Queued loop
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234 delay ImpDef.Minimum_Task_Switch;
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235 end loop;
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236
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237 if Disk_Device.TC_Track /= Initial_Track then
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238 Report.Failed ("Target entry of requeue executed prematurely");
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239 elsif IO_Request'Terminated then
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240 Report.Failed ("Caller did not remain blocked after " &
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241 "the requeue or was never requeued");
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242 else
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243
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244 -- Verify (C): that IO_Request is queued on the
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245 -- Pending_Read entry queue.
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246 --
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247 -- Set the barrier for Pending_Read to true. Check that the
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248 -- current track is updated and that IO_Request terminates.
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249
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250 Disk_Device.Disk_Interrupt; -- Simulate a disk interrupt,
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251 -- signaling that the head is
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252 -- over the correct track.
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253
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254 -- The Pending_Read entry body will complete before the next
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255 -- protected action is called (Disk_Device.TC_Track).
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256
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257 if Disk_Device.TC_Track /= New_Track then
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258 Report.Failed ("Caller was not requeued on target entry");
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259 end if;
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260
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261 -- Finally, verify (D): that Read_Task continues after Pending_Read
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262 -- completes.
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263 --
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264 -- Note that the test will hang here if Read_Task does not continue
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265 -- executing following the completion of the requeued entry call.
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266
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267 end if;
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268
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269 end; -- We will not exit the declare block until the task completes
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270
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271 Report.Result;
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272
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273 end C954001;
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