1-- C954A03.A 2-- 3-- Grant of Unlimited Rights 4-- 5-- Under contracts F33600-87-D-0337, F33600-84-D-0280, MDA903-79-C-0687, 6-- F08630-91-C-0015, and DCA100-97-D-0025, the U.S. Government obtained 7-- unlimited rights in the software and documentation contained herein. 8-- Unlimited rights are defined in DFAR 252.227-7013(a)(19). By making 9-- this public release, the Government intends to confer upon all 10-- recipients unlimited rights equal to those held by the Government. 11-- These rights include rights to use, duplicate, release or disclose the 12-- released technical data and computer software in whole or in part, in 13-- any manner and for any purpose whatsoever, and to have or permit others 14-- to do so. 15-- 16-- DISCLAIMER 17-- 18-- ALL MATERIALS OR INFORMATION HEREIN RELEASED, MADE AVAILABLE OR 19-- DISCLOSED ARE AS IS. THE GOVERNMENT MAKES NO EXPRESS OR IMPLIED 20-- WARRANTY AS TO ANY MATTER WHATSOEVER, INCLUDING THE CONDITIONS OF THE 21-- SOFTWARE, DOCUMENTATION OR OTHER INFORMATION RELEASED, MADE AVAILABLE 22-- OR DISCLOSED, OR THE OWNERSHIP, MERCHANTABILITY, OR FITNESS FOR A 23-- PARTICULAR PURPOSE OF SAID MATERIAL. 24--* 25-- 26-- OBJECTIVE: 27-- Check that a requeue statement in an accept_statement with 28-- parameters may requeue the entry call to a protected entry with no 29-- parameters. Check that, if the call is queued on the new entry's 30-- queue, the original caller remains blocked after the requeue, but 31-- the accept_statement containing the requeue is completed. 32-- 33-- Note that this test uses a requeue "with abort," although it does not 34-- check that such a requeued caller can be aborted; that feature is 35-- tested elsewhere. 36-- 37-- TEST DESCRIPTION: 38-- Declare a protected type which simulates a printer device driver 39-- (foundation code). 40-- 41-- Declare a task which simulates a printer server for multiple printers. 42-- 43-- For the protected type, declare an entry with a barrier that is set 44-- false by a protected procedure (which simulates starting a print job 45-- on the printer), and is set true by a second protected procedure (which 46-- simulates a handler called when the printer interrupts, indicating 47-- that printing is done). 48-- 49-- For the task, declare an entry whose corresponding accept statement 50-- contains a call to first protected procedure of the protected type 51-- (which sets the barrier of the protected entry to false), followed by 52-- a requeue with abort to the protected entry. Declare a second entry 53-- which does nothing. 54-- 55-- Declare a "requesting" task which calls the printer server task entry 56-- (and thus executes the requeue). Verify that, following the requeue, 57-- the requesting task remains blocked. Call the second entry of the 58-- printer server task (the acceptance of this entry call verifies that 59-- the requeue statement completed the entry call by the requesting task. 60-- Call the second protected procedure of the protected type (the 61-- interrupt handler) and verify that the protected entry completes for 62-- the requesting task (which verifies that the requeue statement queued 63-- the first task object to the protected entry). 64-- 65-- TEST FILES: 66-- This test depends on the following foundation code: 67-- 68-- F954A00.A 69-- 70-- 71-- CHANGE HISTORY: 72-- 06 Dec 94 SAIC ACVC 2.0 73-- 10 Oct 96 SAIC Added pragma elaborate. 74-- 75--! 76 77package C954A03_0 is -- Printer server abstraction. 78 79 -- Simulate a system with multiple printers. The entry Print requests 80 -- that data be printed on the next available printer. The entry call 81 -- is accepted when a printer is available, and completes when printing 82 -- is done. 83 84 task Printer_Server is 85 entry Print (File_Name : String); -- Test the requeue statement. 86 entry Verify_Results; -- Artifice for test purposes. 87 end Printer_Server; 88 89end C954A03_0; 90 91 92 --==================================================================-- 93 94 95with Report; 96with ImpDef; 97 98with F954A00; -- Printer device abstraction. 99use F954A00; 100pragma Elaborate(F954a00); 101 102package body C954A03_0 is -- Printer server abstraction. 103 104 105 task body Printer_Server is 106 Printers_Busy : Boolean := True; 107 Index : Printer_ID := 1; 108 Print_Accepted : Boolean := False; 109 begin 110 111 loop 112 -- Wait for a printer to become available: 113 114 while Printers_Busy loop 115 Printers_Busy := False; -- Exit loop if 116 -- entry accepted. 117 select 118 Printer(Index).Done_Printing; -- Accepted immed. 119 -- when printer is 120 -- available. 121 else 122 Index := 1 + (Index mod Number_Of_Printers);-- Entry not immed. 123 Printers_Busy := True; -- accepted; keep 124 end select; -- looping. 125 126 -- Allow other tasks to get control 127 delay ImpDef.Minimum_Task_Switch; 128 129 end loop; 130 -- Value of Index 131 -- at loop exit 132 -- identifies the 133 -- avail. printer. 134 135 -- Wait for a print request or terminate: 136 137 select 138 accept Print (File_Name : String) do 139 Print_Accepted := True; -- Allow 140 -- Verify_Results 141 -- to be accepted. 142 143 Printer(Index).Start_Printing (File_Name); -- Begin printing on 144 -- the available 145 -- -- -- printer. 146 -- Requeue is tested here -- 147 -- -- 148 -- Requeue caller so 149 requeue Printer(Index).Done_Printing -- server task free 150 with abort; -- to accept other 151 end Print; -- requests. 152 or 153 -- Guard ensures that Verify_Results cannot be accepted 154 -- until after Print has been accepted. This avoids a 155 -- race condition in the main program. 156 157 when Print_Accepted => accept Verify_Results; -- Artifice for 158 -- testing purposes. 159 or 160 terminate; 161 end select; 162 163 end loop; 164 165 exception 166 when others => 167 Report.Failed ("Exception raised in Printer_Server task"); 168 end Printer_Server; 169 170 171end C954A03_0; 172 173 174 --==================================================================-- 175 176 177with Report; 178with ImpDef; 179 180with F954A00; -- Printer device abstraction. 181with C954A03_0; -- Printer server abstraction. 182 183use C954A03_0; 184use F954A00; 185 186procedure C954A03 is 187 188 Long_Enough : constant Duration := ImpDef.Clear_Ready_Queue; 189 190 191 --==============================================-- 192 193 Task_Completed : Boolean := False; -- Testing flag. 194 195 protected Interlock is -- Artifice for test purposes. 196 entry Wait; -- Wait for lock to be released. 197 procedure Release; -- Release the lock. 198 private 199 Locked : Boolean := True; 200 end Interlock; 201 202 203 protected body Interlock is 204 205 entry Wait when not Locked is -- Calls are queued until after 206 -- -- Release is called. 207 begin 208 Task_Completed := True; 209 end Wait; 210 211 procedure Release is -- Called by Print_Request. 212 begin 213 Locked := False; 214 end Release; 215 216 end Interlock; 217 218 --==============================================-- 219 220 task Print_Request is -- Send a print request. 221 end Print_Request; 222 223 task body Print_Request is 224 My_File : constant String := "MYFILE.DAT"; 225 begin 226 Printer_Server.Print (My_File); -- Invoke requeue statement. 227 Interlock.Release; -- Allow main to continue. 228 exception 229 when others => 230 Report.Failed ("Exception raised in Print_Request task"); 231 end Print_Request; 232 233 --==============================================-- 234 235begin -- Main program. 236 237 Report.Test ("C954A03", "Requeue from an Accept with parameters" & 238 " to a Protected Entry without parameters"); 239 240 -- To pass this test, the following must be true: 241 -- 242 -- (A) The Print entry call made by the task Print_Request must be 243 -- completed by the requeue statement. 244 -- (B) Print_Request must remain blocked following the requeue. 245 -- (C) Print_Request must be queued on the Done_Printing queue of 246 -- Printer(1). 247 -- (D) Print_Request must continue execution after Done_Printing is 248 -- complete. 249 -- 250 -- First, verify (A): that the Print entry call is complete. 251 -- 252 -- Call the entry Verify_Results. If the requeue statement completed the 253 -- entry call to Print, the entry call to Verify_Results should be 254 -- accepted. Since the main will hang if this is NOT the case, make this 255 -- a timed entry call. 256 257 select 258 Printer_Server.Verify_Results; -- Accepted if requeue completed 259 -- entry call to Print. 260 or 261 delay Long_Enough; -- Time out otherwise. 262 Report.Failed ("Requeue did not complete entry call"); 263 end select; 264 265 -- Now verify (B): that Print_Request remains blocked following the 266 -- requeue. Also verify that Done_Printing (the entry to which 267 -- Print_Request should have been queued) has not yet executed. 268 269 if Printer(1).Is_Done then 270 Report.Failed ("Target entry of requeue executed prematurely"); 271 elsif Print_Request'Terminated then 272 Report.Failed ("Caller did not remain blocked after the requeue"); 273 else 274 275 -- Verify (C): that Print_Request is queued on the 276 -- Done_Printing queue of Printer(1). 277 -- 278 -- Set the barrier for Printer(1).Done_Printing to true. Check 279 -- that the Done flag is updated and that Print_Request terminates. 280 281 Printer(1).Handle_Interrupt; -- Simulate a printer interrupt, 282 -- signaling that printing is 283 -- done. 284 285 -- The Done_Printing entry body will complete before the next 286 -- protected action is called (Printer(1).Is_Done). 287 288 if not Printer(1).Is_Done then 289 Report.Failed ("Caller was not requeued on target entry"); 290 end if; 291 292 -- Finally, verify (D): that Print_Request continues after Done_Printing 293 -- completes. 294 -- 295 -- After Done_Printing completes, there is a potential race condition 296 -- between the main program and Print_Request. The protected object 297 -- Interlock is provided to ensure that the check of whether 298 -- Print_Request continued is made *after* it has had a chance to do so. 299 -- The main program waits until the statement in Print_Request following 300 -- the requeue-causing statement has executed, then checks to see 301 -- whether Print_Request did in fact continue executing. 302 -- 303 -- Note that the test will hang here if Print_Request does not continue 304 -- executing following the completion of the requeued entry call. 305 306 Interlock.Wait; -- Wait until Print_Request is 307 -- done. 308 if not Task_Completed then 309 Report.Failed ("Caller remained blocked after target " & 310 "entry released"); 311 end if; 312 313 -- Wait for Print_Request to finish before calling Report.Result. 314 while not Print_Request'Terminated loop 315 delay ImpDef.Minimum_Task_Switch; 316 end loop; 317 318 end if; 319 320 Report.Result; 321 322end C954A03; 323