RFR 8211736: jdb doesn't print prompt when breakpoint is hit and suspend policy is STOP_EVENT_THREAD

[Gary Adams]

Back in July, I tried to address the jdb output synchronization problem
by buffering the output from commands and events.

   http://cr.openjdk.java.net/~gadams/8169718/webrev.01/

The changes were very invasive and only provided a partial solution.

Bottom line for me is the fact that the jdb commands, replies and prompts
were never designed as a rigid protocol. They were designed to be 
interactive
with a user and guiding them through a debugging session.

The tests that process jdb commands are fragile, because they run
much quicker than user interactive speeds, so race conditions can be 
observed.
Also, the reliance on a single standard output stream allows for 
interspersed
output.

I think we are pretty close to reaching the current test stabilization 
goals and
this area doesn't really merit additional investment at this time.

On 10/17/18, 1:47 PM, Chris Plummer wrote:
> Hi Alex,
>
> I think the tty buffering should be a separate bug fix, and I'd also 
> like input from Gary on it since he had tried something similar at one 
> point. It should probably also include a multithread test to prove the 
> fix is working (after first getting the test to fail without the 
> changes).
>
> thanks,
>
> Chris
>
> On 10/16/18 8:59 PM, Daniil Titov wrote:
>> Hi Alex, Chris and JC,
>>
>> Please review an updated version of the patch that addresses these 
>> issues.
>>
>> Webrev: http://cr.openjdk.java.net/~dtitov/8211736/webrev.03/
>> Issue:  https://bugs.openjdk.java.net/browse/JDK-8211736
>>
>> Thanks!
>> --Daniil
>>
>>
>> On 10/12/18, 9:52 AM, "Alex Menkov" <alexey.menkov at oracle.com> wrote:
>>
>>      Hi Daniil,
>>           1) +1 for printCurrentLocation when suspendPolicy != 
>> SUSPEND_ALL
>>           2) wrong indent in JdbStopThreadTest.java:
>>         36         import lib.jdb.JdbCommand;
>>         37         import lib.jdb.JdbTest;
>>           3) I think it would be better to make waitForSimplePrompt 
>> property of
>>      JdbCommand (like JdbCommand.allowExit)
>>           jdb.command(JdbCommand.run().replyIsSimplePrompt());
>>      looks much clearer than
>>      jdb.command(JdbCommand.run(), true);
>>           4) (TTY.java)
>>          MessageOutput.lnprint("Breakpoint hit:");
>>      +  // Print current location and prompt if suspend policy is
>>      SUSPEND_EVENT_THREAD.
>>      +  // In case of SUSPEND_ALL policy this is handled by 
>> vmInterrupted()
>>      method.
>>      +  if (be.request().suspendPolicy() == 
>> EventRequest.SUSPEND_EVENT_THREAD) {
>>      +      printCurrentLocation(ThreadInfo.getThreadInfo(be.thread()));
>>      +      MessageOutput.printPrompt();
>>      +  }
>>      We have 3 separate outputs.
>>      If we have several concurrent threads, we can easy get mess of 
>> outputs
>>      from different threads.
>>      I think it would be better to print everything in a single chunk.
>>      I suppose TTY has other places with similar "non-atomic" output, so
>>      maybe revising TTY output should be handled by separate issue.
>>           --alex
>>           On 10/11/2018 22:00, Chris Plummer wrote:
>> > Hi Daniil,
>> >
>> > Can you send output from an example jdb session?
>> >
>> > Do you think maybe we should also call printCurrentLocation() when the
>> > suspend policy is NONE?
>> >
>> > There's a typo in the following line. The space is on the wrong 
>> side of
>> > the comma.
>> >
>> >    72         jdb.command(JdbCommand.stopThreadAt(DEBUGGEE_CLASS 
>> ,bpLine));
>> >
>> > thanks,
>> >
>> > Chris
>> >
>> > On 10/11/18 8:02 PM, Daniil Titov wrote:
>> >>
>> >> Thank you,  JC!
>> >>
>> >> Please review an updated version of the patch that fixes newly added
>> >> test for Windows platform  (now it uses system dependent line
>> >> separator string).
>> >>
>> >> Webrev:http://cr.openjdk.java.net/~dtitov/8211736/webrev.02/
>> >> <http://cr.openjdk.java.net/%7Edtitov/8211736/webrev.02/>
>> >>
>> >> Issue: https://bugs.openjdk.java.net/browse/JDK-8211736
>> >>
>> >> Best regards,
>> >>
>> >> --Daniil
>> >>
>> >> *From: *JC Beyler <jcbeyler at google.com>
>> >> *Date: *Thursday, October 11, 2018 at 7:17 PM
>> >> *To: *<daniil.x.titov at oracle.com>
>> >> *Cc: *<serviceability-dev at openjdk.java.net>
>> >> *Subject: *Re: RFR 8211736: jdb doesn't print prompt when breakpoint
>> >> is hit and suspend policy is STOP_EVENT_THREAD
>> >>
>> >> Hi Daniil,
>> >>
>> >> Looks good to me. I saw a really small nit:
>> >>
>> >> 
>> http://cr.openjdk.java.net/~dtitov/8211736/webrev.01/test/jdk/com/sun/jdi/JdbStopThreadTest.java.html
>> >> 
>> <http://cr.openjdk.java.net/%7Edtitov/8211736/webrev.01/test/jdk/com/sun/jdi/JdbStopThreadTest.java.html>
>> >>
>> >> 70  jdb.command(JdbCommand.stopThreadAt( DEBUGGEE_CLASS ,bpLine));
>> >>
>> >> There is a space after the '('.
>> >>
>> >> No need to send a new webrev for that evidently :),
>> >>
>> >> Jc
>> >>
>> >> On Thu, Oct 11, 2018 at 5:07 PM Daniil Titov
>> >> <daniil.x.titov at oracle.com <mailto:daniil.x.titov at oracle.com>> wrote:
>> >>
>> >>     Please review the change that fixes the issue with missing prompt
>> >>     in jdb when a breakpoint is hit and the suspend policy is set to
>> >>     stop the thread only.
>> >>
>> >>     Webrev: http://cr.openjdk.java.net/~dtitov/8211736/webrev.01
>> >> <http://cr.openjdk.java.net/%7Edtitov/8211736/webrev.01>
>> >>     Issue: https://bugs.openjdk.java.net/browse/JDK-8211736
>> >>
>> >>     Thanks!
>> >>     --Daniil
>> >>
>> >>
>> >>
>> >> --
>> >>
>> >> Thanks,
>> >>
>> >> Jc
>> >>
>> >
>>
>>
>
>