On 10/2/19 1:57 AM, Severin Gehwolf wrote:
On Wed, 2019-10-02 at 10:39 +0200, Severin Gehwolf wrote:
On Tue, 2019-10-01 at 12:51 -0700, Chris Plummer wrote:
Hi Severin,
Sorry, this is not an area that I have any expertise in. However, I did
confirm that it fixes the NPE I was seeing with JShellHeapDumpTest.java,
which brings up a question. You said this happens with -Xcomp, but I was
never using -Xcomp. Might it also be triggered without -Xcomp?
Yes, as soon as C1/C2 kick in you might be seeing the issue. In fact, I
had one reproducer which triggered the issue quite reliably which
didn't use -Xcomp explicitly. Nevertheless, certain methods got JIT
compiled soon and the issue surfaced. You should be able to verify by
adding -XX:+PrintCompilation to the host program and/or comparing it to
-Xint runs.
TLDR; -Xcomp helps reproducing the issue on smaller test cases, but
isn't essential in the general case.
On second thought, I haven't investigated whether running the SA on a
heap dump triggers the issue as well. There might be another code path
not covered with this patch. If there still is, it might be a similar,
but slightly different bug.
So you are saying your fix here is for when producing the heap dump,
but parsing the heap dump might also have a similar issue? I think we
are not seeing any issue with the parsing. My new
HeapDumpTestWithActiveProcess.java test used to reproduce the NPE when
dumping the heap, and your fix has resolved that issue. The test then
goes on to dump all the stacks in the heap dump, so I think if there was
a problem we would have seen it.
Chris
Thanks,
Severin
