Jim writes:
> Um, seeing as how I wrote my own ONLINE program using HPDEVCONTROL,
> which we rely on in our production environment, could you disclose
> what the bugs are and what versions have these bugs?
Ok, you made me realize that my posting of these comments was
quite a while ago...much longer than I thought! (Probably back
around MPE XL 4.0!)
So, revised & expanded comments below, after "----" line.
> Oh, and by the way, would you like to explain to the uninitiated (that's
> me) what waiting for the AVR does? I checked my utility using SHOWDEV.
> With a tape loaded, but offline, SHOWDEV 7 gives:
...
> Immediatley after running my ONLINE utility:
>
> :SHOWDEV 7
> 7 UNAVAIL SYS
>
> Repeated SHOWDEV's finally give:
> 7 AVAIL (W) (Nolabel) 1600
>
> Is this what you mean by waiting for AVR? Does your utility not
> return until the tape is ready to be written to/read from?
Yes. This is fairly tricky, because we index into an old Compatibility
Mode table (the LDT (Logical Device Table)) and watch the "density"
field...when it becomes non-0, the tape is AVR'd. (Code written by
Charlie Rand of Allegro ... we only hire intrinsics :)
----------------------------------------------------------------------
First, a <plug> CSEQ Tool </plug> look at HPDEVCONTROL:
:cseq HPDEVCONTROL
Procedure HPDEVCONTROL (
status : anyvar record ; {R26, @32 -> 32, align 32}
ldev_ca : anyvar record ; {R25, @32 -> 8208}
itemnum : int32 ; {R24}
item : anyvar int32 ) {R23}
{ }
{NOTE: NOTE: NOTE: }
{ *SERIOUS* problems can occur if the status }
{ parameter is not 4-byte aligned! }
{ }
{NOTE: }
{ The intrinsic definition of this procedure may }
{ *not* match reality! (As of early MPE/iX 4.0) }
{ (appears fixed by 5.0) }
{The "itemnum" parameter is actually by-value, and}
{the NL.PUB.SYS entry is uppercase "HPDEVCONTROL".}
{ }
{ldev_ca: -###- e.g.,: x7x or "123" }
{itemnums: }
{ 100 i32 Load Media (tapes only?) }
{ 101 i32 Online (DDS, some tapes) }
{ }
{Not supported on 7974, 7976 tape drives. }
{Item 101 not supported for 7978 tape drives. }
uncheckable_anyvar
Ok, we so already know that there are various problems
with HPDEVCONTROL.
The "SERIOUS" problem I refer to is: system failure.
HPDEVCONTROL had (and still has) a bug that can result
in a system failure (even on MPE/iX 5.5 PowerPatch 1).
As the above notes, the intrinsic definition of HPDEVCONTROL
was wrong for a couple of releases of MPE, which resulted
in it being even easier to kill the system.
Here are other things I've found:
HP7978B tape drives cannot be put on-line programmatically.
Using ONLINE for an HP7978B will result in an "LDEV NOT READY"
message on the system console, and will probably require you
to <break>/ABORT ONLINE.
HP7980XC tape drives may require that you break/abort ONLINE
and run it a second time if tape data compression is enabled.
If the tape is not mounted, this program will hang until it is
mounted, or an ABORTIO is done on the ldev (or until you hit
<break> and enter: ABORT). Sorry, but this is a shortcoming
in the design of the awkward HP intrinsic ONLINE calls. If an
ABORTIO is done, the intrinsic returns the incorrect
"warning": "The operation was successful with retries.",
which, of course, it wasn't.
If the ldev you specify is not a tape drive, ONLINE may
generate a misleading error. Again, this is the fault of the
intrinsic. ONLINE attempts to avoid this by using simple
privileged code to check the type of ldev you specify. (#1)
If you try to place a tape on-line after another process has
already "grabbed" the drive, your request will be rejected
with error -3/$8f, and the tape may have to be placed on-line
manually. (Again, due to the intrinsic.) (If you do an
ABORTIO after running ONLINE in this case, the online-request
may be belatedly honored by the drive.)
The above hard-won information, and more, is reflected in the
following pseudo-code:
hpdevcontrol (status, ldevname', i'online, dummy);
if status = $ffdf0071 then
begin ! seen when trying to put tape on-line after SCSIDDS
! diagnostic used it ... then, a second attempt worked
! SS 930916
wait'secs := 1.0;
pause (wait'secs);
status := 0d;
hpdevcontrol (status, buf', i'online, dummy);
end;
if status <> 0d then
begin
if status = $ffdd0071 then
begin
! $ffdd0071 not reportable via hperrmsg :(
"LLIO Internal error # -35"
" "
"The above error seems to occur when an HP7978 tape drive is"
"placed on-line manually."
end
else if status = $ffff0071 then
begin
hperrmsg (2d, 1d, , status, , , hperrmsg'status);
" "
"The above error/message is misleading. It typically is returned
"when an ABORTIO command cancelled the on-line request."
end
else if status = $fffd008f then
begin
hperrmsg (2d, 1d, , status, , , hperrmsg'status);
" " ! blank line
"The above error is typically returned when you try to place on-line
"a tape drive that has already been allocated to a process. The
"intrinsic ONLINE uses can't handle that situation."
end
else
begin
hperrmsg (2d, 1d, , status, , , hperrmsg'status);
" "
...failed for unknown HPDEVCONTROL reason
end
end
else
begin
... "online" succeeded ...
while remaining'avr'attempts > 0 do
see if AVR done;
if not, pause 1 second
decrement remaining'avr'attempts
end;
---------------------------------------------------------------
1991-05-17 notes...
Sample ldevs and hpdevcontrol results on Lisa (3000/917):
Ldev Type Result (hpdevcontrol status -> hperrmsg)
---- ---- ----------------------------------------
1 Disc There is marginal data on disc. BAD INFO!
99 (none) Intrinsic layer; an undefined error occurred.
7 DDS: various:
loaded & online: ok (status = 0)
loaded & offline: ok (status = 0)
not loaded: hang until loaded or I/O is aborted:
if loaded: ok (status = 0)
if aborted: The operation was successful
with retries. BAD INFO!
---------------------------------------------------------------
Because of the misleading information returned by HPDEVCONTROL
when a bad ldev is passed to it, I wrote:
equate
! Values returned by io_device_class ...
! chosen by MPE, not me!
io_not_configured = 0,
io_disc = 1,
io_tape = 2,
io_terminal = 3,
io_printer = 4,
io_serial_printer = 5,
io_spooler = 6,
io_data_comm = 7,
io_ds_term = 8,
io_ds_printer = 9,
io_user_device = 10,
integer Procedure io_device_class (ldev); ! an MPE internal
value ldev; ! must be in PM to call!
integer ldev;
option native, nocc, external;
<<************************************************************>>
procedure check'legal'ldev (ldev);
value ldev;
integer ldev;
option privileged, native, nocc;
! Makes sure "ldev" is a valid, configured tape...
! note the "privileged". The COBOL equivalent would be
! something vaguely like:
! call intrinsic "GETPRIVMODE".
! call "io_device_class" with \ldev\ giving devclass.
! call intrinsic "GETUSERMODE".
begin
logical
dc;
if ldev <= 0 then
begin
"LDEV must be > 0" ;
die (3);
end;
dc := io_device_class (ldev);
if dc = io_not_configured then
begin
"LDEV not configured" ;
die (5);
end;
if dc <> io_tape then
begin
"LDEV does not appear to be a tape drive" ;
die (6);
end;
end <<check'legal'ldev proc>>;
<<************************************************************>>
--
Stan Sieler [log in to unmask]
http://www.allegro.com/sieler.html
|
