RFR: 8294580: frame::interpreter_frame_print_on() crashes if free BasicObjectLock exists in frame

[Martin Doerr]

On Thu, 29 Sep 2022 12:49:27 GMT, Richard Reingruber <rrich at openjdk.org> wrote:

> Add null check before dereferencing BasicObjectLock::_obj.
> BasicObjectLocks are marked as free by setting _obj to null.
> 
> I've done manual testing:
> 
> 
> ./images/jdk/bin/java -Xlog:continuations=trace -XX:+VerifyContinuations --enable-preview VTSleepAfterUnlock
> 
> 
> with the test attached to the JBS item.
> 
> Example output:
> 
> 
> [0.349s][trace][continuations] Interpreted frame (sp=0x000000011d5c6398 unextended sp=0x000000011d5c63b8, fp=0x000000011d5c6420, real_fp=0x000000011d5c6420, pc=0x00007f0ff0199c6a)
> [0.349s][trace][continuations] ~return entry points  [0x00007f0ff0199820, 0x00007f0ff019a2e8]  2760 bytes
> [0.349s][trace][continuations]  - local  [0x000000011d5c3550]; #0
> [0.349s][trace][continuations]  - local  [0x000000011d5c3550]; #1
> [0.349s][trace][continuations]  - local  [0x0000000000000000]; #2
> [0.349s][trace][continuations]  - stack  [0x0000000000000064]; #1
> [0.349s][trace][continuations]  - stack  [0x0000000000000000]; #0
> [0.349s][trace][continuations]  - obj    [null]
> [0.349s][trace][continuations]  - lock   [monitor mark(is_neutral no_hash age=0)]
> [0.349s][trace][continuations]  - monitor[0x000000011d5c63d8]
> [0.349s][trace][continuations]  - bcp    [0x00007f0fa8400401]; @17
> [0.349s][trace][continuations]  - locals [0x000000011d5c6440]
> [0.349s][trace][continuations]  - method [0x00007f0fa8400430]; virtual void VTSleepAfterUnlock.sleepAfterUnlock()

LGTM. Thanks for fixing!

-------------

Marked as reviewed by mdoerr (Reviewer).

PR: https://git.openjdk.org/jdk/pull/10486