3 -- Grant of Unlimited Rights
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
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.
27 -- Check that a requeue statement within an entry_body with parameters
28 -- may requeue the entry call to a protected entry with a subtype-
29 -- conformant parameter profile. Check that, if the call is queued on the
30 -- new entry's queue, the original caller remains blocked after the
31 -- requeue, but the entry_body containing the requeue is completed.
34 -- Declare a protected object which simulates a disk device. Declare an
35 -- entry that requeues the caller to a second entry if the disk head is
36 -- not in the proper location, but first sets the second entry's barrier
37 -- to false. Declare a procedure which sets the second entry's barrier
40 -- Declare a task which calls the first entry such that the requeue is
41 -- called. This task should be queued on the second entry and remain
42 -- blocked, and the first entry should be complete. Call the procedure
43 -- which releases the second entry's queue. The second entry should
44 -- complete, after which the task should complete.
48 -- 06 Dec 94 SAIC ACVC 2.0
52 package C954001_0
is -- Disk management abstraction.
55 -- Simulate a read-only disk device with a head that may be moved to
56 -- different tracks. If a read request is issued for the current
57 -- track, the request can be satisfied immediately. Otherwise, the head
58 -- must be moved to the correct track, during which time the calling task
59 -- is blocked. When the head reaches the correct track, the disk generates
60 -- an interrupt, after which the request can be satisfied, and the
61 -- calling task can proceed.
63 Buffer_Size
: constant := 100;
65 type Disk_Buffer
is new String (1 .. Buffer_Size
);
66 type Disk_Track
is new Natural;
68 type Disk_Address
is record
70 -- Additional components.
73 Initial_Track
: constant Disk_Track
:= 0;
74 New_Track
: constant Disk_Track
:= 5;
76 --==============================================--
78 protected Disk_Device
is
80 entry Read
(Where
: Disk_Address
; -- Read data from disk
81 Data
: out Disk_Buffer
); -- track.
83 procedure Disk_Interrupt
; -- Handle interrupt
86 function TC_Track
return Disk_Track
; -- Return current track.
88 function TC_Pending_Queued
return Boolean; -- True when there is
93 entry Pending_Read
(Where
: Disk_Address
; -- Wait for head to
94 Data
: out Disk_Buffer
); -- move then read data.
96 Current_Track
: Disk_Track
:= Initial_Track
; -- Current disk track.
97 Operation_Pending
: Boolean := False; -- Vis. entry barrier.
98 Disk_Interrupted
: Boolean := False; -- Priv. entry barrier.
106 --==================================================================--
109 package body C954001_0
is -- Disk management abstraction.
112 protected body Disk_Device
is
114 entry Read
(Where
: Disk_Address
; Data
: out Disk_Buffer
)
115 when not Operation_Pending
is
117 if (Where
.Track
= Current_Track
) then -- If the head is over the
118 -- Read data from disk... -- requested track, read
121 else -- Otherwise, defer read
122 Operation_Pending
:= True; -- while head is moved to
123 -- correct track (signaled
124 -- -- -- by a disk interrupt).
125 -- Requeue is tested here --
128 requeue Pending_Read
;
134 procedure Disk_Interrupt
is -- Called when the disk
135 begin -- interrupts, indicating
136 Disk_Interrupted
:= True; -- that the head is over
137 end Disk_Interrupt
; -- the correct track.
140 function TC_Track
return Disk_Track
is -- Artifice required for
141 begin -- testing purposes.
142 return (Current_Track
);
146 entry Pending_Read
(Where
: Disk_Address
; Data
: out Disk_Buffer
)
147 when Disk_Interrupted
is
149 Current_Track
:= Where
.Track
; -- Head is now over the
150 -- Read data from disk... -- correct track; read
151 Operation_Pending
:= False; -- the data.
152 Disk_Interrupted
:= False;
155 function TC_Pending_Queued
return Boolean is
157 -- Return true when there is something on the Pending_Read queue
158 return (Pending_Read
'Count /=0);
159 end TC_Pending_Queued
;
167 --==================================================================--
173 with C954001_0
; -- Disk management abstraction.
179 task type Read_Task
is -- an unusual (but legal) declaration
183 task body Read_Task
is
184 Location
: constant Disk_Address
:= (Track
=> New_Track
);
185 Data
: Disk_Buffer
:= (others => ' ');
187 Disk_Device
.Read
(Location
, Data
); -- Invoke requeue statement.
190 Report
.Failed
("Exception raised in task");
193 --==============================================--
195 begin -- Main program.
197 Report
.Test
("C954001", "Requeue from an entry within a P.O. " &
198 "to a private entry within the same P.O.");
203 IO_Request
: Read_Task
; -- Request a read from other
204 -- than the current track.
205 -- IO_Request will be requeued
206 -- from Read to Pending_Read.
209 -- To pass this test, the following must be true:
211 -- (A) The Read entry call made by the task IO_Request must be
212 -- completed by the requeue.
213 -- (B) IO_Request must remain blocked following the requeue.
214 -- (C) IO_Request must be queued on the Pending_Read entry queue.
215 -- (D) IO_Request must continue execution after the Pending_Read
218 -- First, verify (A): that the Read entry call is complete.
220 -- Call a protected operation (Disk_Device.TC_Track). Since no two
221 -- protected actions may proceed concurrently unless both are protected
222 -- function calls, a call to a protected operation at this point can
223 -- proceed only if the Read entry call is already complete.
225 -- Note that if Read is NOT complete, the test will likely hang here.
227 -- Next, verify (B): that IO_Request remains blocked following the
228 -- requeue. Also verify that Pending_Read (the entry to which
229 -- IO_Request should have been queued) has not yet executed.
231 -- Wait until the task had made the call and the requeue has been
233 while not Disk_Device
.TC_Pending_Queued
loop
234 delay ImpDef
.Minimum_Task_Switch
;
237 if Disk_Device
.TC_Track
/= Initial_Track
then
238 Report
.Failed
("Target entry of requeue executed prematurely");
239 elsif IO_Request
'Terminated then
240 Report
.Failed
("Caller did not remain blocked after " &
241 "the requeue or was never requeued");
244 -- Verify (C): that IO_Request is queued on the
245 -- Pending_Read entry queue.
247 -- Set the barrier for Pending_Read to true. Check that the
248 -- current track is updated and that IO_Request terminates.
250 Disk_Device
.Disk_Interrupt
; -- Simulate a disk interrupt,
251 -- signaling that the head is
252 -- over the correct track.
254 -- The Pending_Read entry body will complete before the next
255 -- protected action is called (Disk_Device.TC_Track).
257 if Disk_Device
.TC_Track
/= New_Track
then
258 Report
.Failed
("Caller was not requeued on target entry");
261 -- Finally, verify (D): that Read_Task continues after Pending_Read
264 -- Note that the test will hang here if Read_Task does not continue
265 -- executing following the completion of the requeued entry call.
269 end; -- We will not exit the declare block until the task completes