RFR 8163127: Debugger classExclusionFilter does not work correctly with method references

Thu Jan 24 19:19:39 UTC 2019

Hi Daniil,

Thanks for the stack track. I was just about to send an email asking for 
it when your new RFR arrived.

The fix looks good. I think you also need to apply it here:

InterpreterRuntime::ldc()
InterpreterRuntime::anewarray()
InterpreterRuntime::multianewarray()
InterpreterRuntime::quicken_io_cc()

I wonder if it wouldn't be better if you moved the disabling into 
ConstantPool::klass_at_impl()

thanks,

Chris

On 1/24/19 10:38 AM, Daniil Titov wrote:
> Hi Chris and JC,
>
> Thank you for reviewing this change.  Please review a new version of the fix that uses
> the approach Chris suggested ( disabling the single stepping during the class resolution).
>
> Just in case please find below the stack trace for this case when loadClass() method is entered.
>
> #0           SystemDictionary::load_instance_class(Symbol*, Handle, Thread*) at  open/src/hotspot/share/classfile/systemDictionary.cpp:1502
> #1	SystemDictionary::resolve_instance_class_or_null(Symbol*, Handle, Handle, Thread*) at open/src/hotspot/share/classfile/systemDictionary.cpp:853
> #2	SystemDictionary::resolve_instance_class_or_null_helper(Symbol*, Handle, Handle, Thread*) at open/src/hotspot/share/classfile/systemDictionary.cpp:271
> #3	SystemDictionary::resolve_or_null(Symbol*, Handle, Handle, Thread*) at open/src/hotspot/share/classfile/systemDictionary.cpp:254
> #4	SystemDictionary::resolve_or_fail(Symbol*, Handle, Handle, bool, Thread*) at open/src/hotspot/share/classfile/systemDictionary.cpp:202
> #5	ConstantPool::klass_at_impl(constantPoolHandle const&, int, bool, Thread*) at open/src/hotspot/share/oops/constantPool.cpp:483
> #6	ConstantPool::klass_at(int, Thread*) at open/src/hotspot/share/oops/constantPool.hpp:382
> #7	InterpreterRuntime::_new(JavaThread*, ConstantPool*, int) at open/src/hotspot/share/interpreter/interpreterRuntime.cpp:234
> # 8         <Stub Code>
>   ....
>
> Webrev: http://cr.openjdk.java.net/~dtitov/8163127/webrev.02/
> Bug: https://bugs.openjdk.java.net/browse/JDK-8163127
>
> Thanks,
> Daniil
>
> On 1/23/19, 3:53 PM, "Chris Plummer" <chris.plummer at oracle.com> wrote:
>
>      Hi Daniil,
>      
>      I don't see an explanation for why fromDepth is 1 and afterPopDepth is 4.
>      
>               currentDepth = getThreadFrameCount(thread);
>               fromDepth = step->fromStackDepth;
>               afterPopDepth = currentDepth-1;
>      
>      step->fromStackDepth got setup when single stepping was first setup for
>      this thread. There was also a notifyFramePop() done at this time, but I
>      think that's just to catch exiting from the method you were single
>      stepping in, and has no bearing in the case we are looking at here,
>      where we area still some # of frames below where we user last issued a
>      STEP_INTO. The FRAME_POP we are receiving now is not the one for when
>      step->fromStackDepth was setup, but is for when we stepped into a
>      filtered method. I think this is what the "fromDepth > afterPopDepth"
>      check is for. I think the current logic is correct for intended handling
>      of a FRAME_POP event. Although your fix is probably solving the problem,
>      I get the feeling it is enabling single stepping too soon in many cases.
>      That many not turn up as an error in any tests, but could cause
>      debugging performance issues, or for the user to see spurious single
>      step events that they were not expecting.
>      
>      I think the bug actually occurs long before we ever get to this point in
>      the code (and we should in fact not be getting here). In my last entry
>      in the bug I mentioned JvmtiHideSingleStepping(), and how it is used to
>      turn off single stepping while we are doing invoke and field resolution,
>      but doesn't seem to be used during class resolution, which is what we
>      are doing here. If it where used, then the agent would never even see
>      the SINGLE_STEP when loadClass() is entered, therefore no
>      notifyFramePop() would be done, and we would not be relying on this code
>      in handleFramePopEvent(). Instead, we would receive the next SINGLE_STEP
>      event after cp resolution is complete, and we are finally executing the
>      now resolved opc_new opcode.
>      
>      I'm hoping Serguei and/or Alex can also comment on this, since I think
>      they were dealing with JvmtiHideSingleStepping() last month.
>      
>      thanks,
>      
>      Chris
>      
>      
>      
>      On 1/17/19 6:08 PM, Daniil Titov wrote:
>      > Please review the change that fixes JDB stepping issue for a specific case when the single step request was initiated earlier in the stack, previous calls were for methods in the filtered classes (single stepping was disabled), handleMethodEnterEvent() re-enabled stepping and the first bytecode upon entering the current method requires resolving constant pool entry. In this case the execution resumes in java.lang.Classloader.loadClass() and since it is also a filtered class the single stepping is getting disabled again (stepControl.c :593).  When loadClass() exits a notifyFramePop() is called on the loadClass() frame but due to condition fromDepth >= afterPopDepth  at stepControl.c :346 (that doesn't hold in this case, in this case fromDepth is 1 and afterPopDepth  is 4) the notifyFramePop() fails to enable single stepping back. The fix removes the excessive condition fromDepth >= afterPopDepth  in notifyFramePop() method (stepControl.c:346)  to ensure that when a method cal!
>      >   led from the stepping frame (and during which we had stepping disabled) has returned the stepping is re-enabled to continue  instructions steps in the original stepping frame.
>      >
>      > Webrev: http://cr.openjdk.java.net/~dtitov/8163127/webrev.01
>      > Bug: https://bugs.openjdk.java.net/browse/JDK-8163127
>      >
>      > Thanks!
>      > --Daniil
>      >
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