Re: [10] RFR: 8185164: GetOwnedMonitorInfo() returns incorrect owned monitor

[serguei.spit...@oracle.com]

Hi Dan,

Thank you for the test update!
It looks very reasonable to me, the test became pretty solid.

Thanks,
Serguei


On 8/5/17 19:33, Daniel D. Daugherty wrote:

Hi Yasumasa and Serguei,

I've made some tweaks to the test and attached an updated patch:

GetOwnedMonitorInfoTest.java changes:

- deleted thread 't2'
- made changes to make monitor contention not racy:
  - added 'hasEventPosted()' native function
  - changed Main to grab the GetOwnedMonitorInfoTest.class monitor
    before launching 't1'
  - added loop to check hasEventPosted() function while holding
    the GetOwnedMonitorInfoTest.class monitor
  - moved the delay to this new loop

libGetOwnedMonitorInfoTest.c changes:

- added event_has_posted flag to know when MonitorContendedEnter
  event has been posted
- added missing error checks to JVM/TI functions
- print an error message when MonitorContendedEnter or
  MonitorContendedEntered gets an incorrect monitor count
- print error and warnings to 'stderr'
- add Java_GetOwnedMonitorInfoTest_hasEventPosted function

I've tested the latest version of test in a repo without the fix
and it fails (as expected). Here's some sample output:

----------System.out:(7/231)----------
Agent_OnLoad started
Agent_OnLoad finished
Main starting worker thread.
Main waiting for event.
Thread in sync section: Thread-1
MonitorContendedEnter: Thread-1 owns 1 monitor(s)
MonitorContendedEntered: Thread-1 owns 1 monitor(s)
----------System.err:(14/931)----------
MonitorContendedEnter: FAIL: monitorCount should be zero.
java.lang.RuntimeException: FAILED status returned from the agent
        at GetOwnedMonitorInfoTest.main(GetOwnedMonitorInfoTest.java:81)

at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)

        at java.base/java.lang.reflect.Method.invoke(Method.java:564)

at com.sun.javatest.regtest.agent.MainWrapper$MainThread.run(MainWrapper.java:115)

        at java.base/java.lang.Thread.run(Thread.java:844)

JavaTest Message: Test threw exception: java.lang.RuntimeException: FAILED status returned from the agent

JavaTest Message: shutting down test


Dan


On 8/5/17 12:37 PM, serguei.spit...@oracle.com wrote:

Hi Yasumasa,

I use the following script to run the test on linux:

% cat run.sh
#!/bin/sh
  REPO=<my_repo>
  IMAGES=${REPO}/build/linux-x86_64-normal-server-release/images
  export JAVA_HOME=${IMAGES}/jdk
  export LD_LIBRARY_PATH=${IMAGES}/test/hotspot/jtreg/native

  jtreg -J-Dtest.java.opts='-server' \
      -jdk ${JAVA_HOME} \
      -nativepath:${LD_LIBRARY_PATH} \
$REPO/hotspot/test/serviceability/jvmti/GetOwnedMonitorInfo


Thanks,
Serguei


On 8/5/17 06:31, Yasumasa Suenaga wrote:

Hi Serguei,

I uploaded new webrev:
  http://cr.openjdk.java.net/~ysuenaga/JDK-8185164/webrev.01/

I tried to run serviceability/jvmti/GetOwnedMonitorInfo but it is failed because jtreg needs -nativepath option.

But I didn't know what path should I set to -nativepath.


Thanks,

Yasumasa


On 2017/08/05 20:20, serguei.spit...@oracle.com wrote:

Hi Yasumasa,

Please, merge the converted testcase.
It still might need more tweaks though.

Thanks,
Serguei


On 8/5/17 03:18, Yasumasa Suenaga wrote:

Hi Serguei,

Thank you so much!
Should I merge your testcase? Or can you push this change?

I agree to your change as a reviewer.


Yasumasa


On 2017/08/05 11:34, serguei.spit...@oracle.com wrote:

The updated patch attached.
Now the test is passed with the suggested fix and failed without it.

Thanks,
Serguei


On 8/4/17 15:45, serguei.spit...@oracle.com wrote:

On 8/4/17 14:26, Daniel D. Daugherty wrote:

On 8/4/17 3:17 PM, serguei.spit...@oracle.com wrote:

The patch is attached.
It may need some tweaks though.
I was not able to make it fail yet.

I don't think the original test had "failure" detection.
You were just supposed to notice that a pending monitor
was listed under the wrong list.

Nothing is listed.
Strange thing is I do not see the monitor events fired.
I'm using 10 for testing.

Thanks,
Serguei

Dan

On 8/4/17 12:45, Daniel D. Daugherty wrote:

Thanks Serguei!

I happen to be doing a test run this weekend that includes most of the JPDA stack of tests so I'll include the following in my experiment:

$ hg log -v -r tip
changeset:   12872:bb66cd7c61b1
tag:         8185164.patch
tag:         qtip
tag:         tip
user:        dcubed
date:        Fri Aug 04 13:41:29 2017 -0600
files: src/share/vm/runtime/objectMonitor.cpp
description:
imported patch 8185164.patch

That will get the product code changes a complete round of testing

on Solaris X64 at least... :-)

Great!

Thanks,
Serguei

Dan


On 8/4/17 1:31 PM, serguei.spit...@oracle.com wrote:

Dan,

Thank you for letting me know about this discussion.
I'll try to convert the attached test case to the JTreg format.

Thanks,
Serguei


On 8/4/17 11:16, Daniel D. Daugherty wrote:

Adding Serguei to this thread directly since he's back from vacation!

On 7/31/17 10:14 PM, David Holmes wrote:

Hi Dan,

On 26/07/2017 11:52 PM, Daniel D. Daugherty wrote:

On 7/26/17 12:11 AM, David Holmes wrote:

On 26/07/2017 10:27 AM, Yasumasa Suenaga wrote:

Hi Dan,

I've added some analysis to the bug report

Thanks!

I tried to fix this issue in JvmtiEnvBase::get_owned_monitors() at first. But it is difficult because we cannot know pending monitor if thread state is MONITOR_CONTENDED_ENTER when get_owned_monitor() is called.

I need to look closer at this when I get back from vacation next week.

Seems like you're back already. :-)

A pending monitor should not be reported as owned (unless the spec says otherwise) and it seems odd to me to fix the current problem by marking the monitor as pending earlier.

It's the updating of the _current_pending_monitor field that

allows JvmtiEnvBase::get_locked_objects_in_frame() to recognize

that the monitor observed in the frame is only pending and
is not owned.

I put a fairly detailed note in the bug yesterday, but you
should look at that when you're officially back!

Thanks for clarifying things. I also added a comment to the bug report.

I think the fix is sound and prevents anyone from observing the case where the monitor will be seen in the stack-frame, but has not yet been set as the "pending monitor". As far as I can tell it is only this case (GetOwnedMonitorInfo from the contended-monitor event callback in the current thread) that will be able to observe the change.

One scenario that I worry about here is that a GetCurrentContendedMonitor() call on a target thread will now be able to return a non-NULL value for the object, when GetThreadState() will be able to return something other than

blocked (on monitor enter) for the thread.

I don't see anything in the JVM/TI spec that says such a scenario is wrong; I'm only worried about whether we have any tests that would catch this slight change in behavior. In any case, one of these operations has

to "happen first":

  - thread is marked as blocked
  - monitor is flagged as contended

Currently, they happen in the above order and the fix proposes to

change the order and I see no reason not to do it.

I would like the test attached to the bug to be converted into a native JTREG test that lives in hotspot/test/serviceability/jvmti. See the

following test as a possible example:

hotspot/test/serviceability/jvmti/GetNamedModule

for how to do this... I haven't done one of these new native JTREG

tests myself, but I believe Serguei has...

Dan

Thanks,
David

Dan

Thanks,
David

Did you run the jdk repo's com/sun/jdi tests with your fix?

I have not done yet.

I have a trip until 28 July JST. So I will run it after that.

Yasumasa


On 2017/07/26 7:05, Daniel D. Daugherty wrote:

On 7/24/17 8:40 PM, Yasumasa Suenaga wrote:

Hi all,

I tried to get owned monitors in MonitorContendedEnter JVMTI event handler. However GetOwnedMonitorInfo JVMTI function returns a monitor which is

not yet owned.

I attached reproducer to JBS. Please read README.md.

I think GetOwnedMonitorInfo() should not return a pending monitor.

I uploaded webrev. Could you review?

http://cr.openjdk.java.net/~ysuenaga/JDK-8185164/webrev.00/

I hope this fix is applied to 8u or later release.
I cannot access JPRT. So I need a sponsor.

Thanks for the bug report. It's nice to have a test case and a proposed fix all in the bug report! I've added some analysis to the bug report and we'll need to run this fix through Oracle's JPDA test stack which

is not (yet) open.

Did you run the jdk repo's com/sun/jdi tests with your fix?

Dan

Thanks,

Yasumasa