[jdk19] RFR: 8288949: serviceability/jvmti/vthread/ContStackDepthTest/ContStackDepthTest.java failing [v2]

[Erik Österlund]

On Sat, 25 Jun 2022 01:12:57 GMT, Dean Long <dlong at openjdk.org> wrote:

>> Ron Pressler has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Revert "Remove outdated comment"
>>   
>>   This reverts commit 8f571d76e34bc64ceb31894184fba4b909e8fbfe.
>
> src/hotspot/share/code/compiledMethod.cpp line 464:
> 
>> 462:   while(iter.next()) {
>> 463:     if (iter.type() == relocInfo::static_call_type) {
>> 464:       iter.reloc()->clear_inline_cache();
> 
> This relies on code patching, and for correctness the change must be seen by the thread requesting interpreter-only mode.  If this was being done at a safepoint then it would probably be OK.  However, this code seems to be done using a handshake, so I'm not sure if the required serializing instruction is guaranteed to happen (see JDK-8220351).  Maybe this race is OK, as it seems no worse than the scenario described in the description where another thread resets the call site back to the optimized state.

The change is not guaranteed to be seen on a concurrent thread, until the next global handshake operation completes.

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PR: https://git.openjdk.org/jdk19/pull/66