It may be sufficient when the command prompt is delivered
to introduce a brief pause to allow an asynchronous event to
be processed before another command can be sent. e.g.
throttling the stream of commands being sent
diff --git a/test/hotspot/jtreg/vmTestbase/nsk/share/jdb/Jdb.java
b/test/hotspot/jtreg/vmTestbase/nsk/share/jdb/Jdb.java
--- a/test/hotspot/jtreg/vmTestbase/nsk/share/jdb/Jdb.java
+++ b/test/hotspot/jtreg/vmTestbase/nsk/share/jdb/Jdb.java
@@ -348,7 +348,17 @@
int startPos = stdoutBuffer.length();
sendCommand(command);
- return receiveReply(startPos, compoundPromptOnly, count);
+ String[] reply = receiveReply(startPos, compoundPromptOnly, count);
+
+ if (asyncCommand(command)) {
+ // delay to allow debuggee time to process async command
+ try {
+ Thread.sleep(100);
+ } catch (InterruptedException e) {
+ // ignored
+ }
+ }
+ return reply;
}
On 6/6/18, 11:51 AM, Daniel D. Daugherty wrote:
The two prompts are for two different things so I don't think
that removing one of the prompts is the right solution either.
In the case of an asynchronous command like 'cont', you get
the '<prompt=after-cont-command>' right away because the command
processor is ready for another command. You will also get the
'<prompt-after-breakpoint-event-location1>' prompt when the
breakpoint is hit because that identifies the thread that posted
the breakpoint event. If it takes a long time to hit the breakpoint,
then it will be a long time before the breakpoint prompt is seen.
Likewise, if the breakpoint is hit quickly, then the breakpoint
prompt will be seen more quickly and will sometimes interfere with
the command processor prompt. That's normal for an async command.
One possible way to fix this kind of issue is to structure the
test flow to slightly delay the target thread so it takes longer
to get to the breakpoint. '<prompt=after-cont-command>' will have
a better chance to be printed before (and not colliding with) the
'<prompt-after-breakpoint-event-location1>' prompt.
So if the test program has:
<some line of code>; // breakpoint here
change it to something like:
try { Thread.sleep(100); } catch (InterruptedException ie) {};
<some line of code>; // breakpoint here
Of course, I'm assuming here that the test driver code is looking
for the breakpoint to be hit (and not for '<prompt=after-cont-command>').
Jerry and I did find a few jdb based tests looking for the wrong
prompt...
Dan
On 6/2/18 7:02 AM, gary.ad...@oracle.com wrote:
On 6/1/18 6:54 PM, Chris Plummer wrote:
Hi Gary,
I'm a bit unclear on one point. According to your description,
should we be seeing two prompts for commands like "cont", and
"step"? When you say we are expecting:
"Breakpoint hit:" <location>
<prompt>
Isn't it really:
<prompt>
"Breakpoint hit:" <location>
<prompt>
Let me stretch out the log a little bit
The <prompt> is main[1] or Thread-1[1], etc.
and not distinguished for command or event completion.
<prompt>
stop at <location1>
<prompt-after-stop-command>
stop at <location2>
<prompt-after-stop-command>
cont
<prompt=after-cont-command>
cont
"Breakpoint hit:" <location1>
<prompt-after-cont-command>
"Breakpoint hit:"
<prompt-after-breakpoint-event-location1>
<location2>
<prompt-after-breakpoint-event-location2>
The source of the command or event prompts
was verified with a stacktrace in the printPrompt()
method.
I figure this must be the case, because your fix removes the
printing of a prompt, and we still need one prompt, so there must
have been two to start with. I think in the above the last <prompt>
is being produced sequentially right after the "Breakpoint hit:"
output, so is never an issue. The first <prompt> comes from the
printPrompt() call after issuing the "cont" command, and it's
possible to hit the breakpoint and start producing more output
before printPrompt() has completed, thus causing the problem you are
seeing.
printPrompt() is a very quick operation and is not being interrupted.
But the output from the event handler is produced incrementally.
- event header, e.g. "Breakpont hit:", "Step completed:", etc.
- from vmInterrupted()
- printCurrentLocation()
- monitor command output (if any)
- printPrompt()
There seems to be some purpose to printing this first prompt and I'm
not so sure eliminating it is the right thing to do. I think it
might be there to indicate that the command has been initiated,
because there could be some delay before the breakpoint is hit. So
the issue then is how to make sure this prompt appears in the input
stream before any of the "Step completed:" or "Breakpoint hit:"
output. Possibly event processing should be blocked until
executeCommand() completes.
The primary purposes of prompts is for "user interactive" nudge to
type another command.
But the failures are from tests that are using the presence of a
prompt as an ACK of the
last command. This "prompt-protocol", does not include any sequence
numbers ,
does not pair prompt to command or event, and does not block during
any multipart message formation.
To prevent the error we are observing we would have to buffer all of
the event output
"Breakpoint hit:" <location> <monitored-commands>
<prompt for breakpoint event>
Another way to look at the current failure is to say the event
handler output
has been interrupted by a command sent prematurely. This would never
be seen at user speeds typing in commands.
I should also mention any other output from the user application can
also
interfere with the command and event output streams. I have seen
stray prompts in the logs from System.out.println(). That was the
reason earlier I was looking at changing the tests to look for
specific prompts before continuing to the next command.
\gra
thanks,
Chris
On 5/26/18 3:50 AM, gary.ad...@oracle.com wrote:
This is a review request for a previously closed test bug.
The test was recently moved to the open repos, and the
proposed fix is in the open code.
Webrev: http://cr.openjdk.java.net/~gadams/8169718/webrev/
-------- Forwarded Message --------
Subject: RFR: JDK-8169718: nsk/jdb/locals/locals002: ERROR:
Cannot find boolVar with expected value: false
Date: Fri, 25 May 2018 11:35:10 -0400
From: Gary Adams <gary.ad...@oracle.com>
Reply-To: gary.ad...@oracle.com
The jdb tests use stdin to send commands to a jdb process
and parses the stdout to determine if a command was
successful and when the process is prompting for new commands
to be sent.
Some commands are synchronous, so when the command is completed
a new prompt is sent back immediately.
Some commands are asynchronous, so there could be a delay
until a breakpoint is reached. The event handler then sends a prompt
when the application thread is stopped and new jdb commands can be
sent.
The problem causing the intermittent failures was a corruption in the
output stream when prompts were being sent at the wrong times.
Instead of receiving
"Breakpoint hit:" <location>
<prompt>
the log contained
"Breakpoint hit:" <prompt> <location>
Once out of sync, jdb commands were being sent prematurely
and the wrong values were being compared against expected behavior.
The simple fix proposed here recognizes that commands like "cont",
"step" and "next" are asynchronous commands and should not send back
a prompt immediately. Instead. the event handler will deliver the
next prompt
when the next "Breakpoint hit:" or "Step completed:" state change
occurs.
The bulk of the testing was done on windows-x64-debug builds where the
intermittent failures were observed in ~5 in 1000 testruns. The fix
has
also been tested on linux-x64-debug, solaris-sparcv9-debug,
and macosx-x64-debug, even though the failures have never been
reported
against those platforms.
Failures have been observed in many of the nsk/jdb tests with
similar corrupted
output streams, but never directly associated with this issue before.
redefine001, caught_exception002, locals002, eval001, next001,
stop_at003, step002, print002, trace001, step_up001, read001,
clear004, kill001, set001
