RFR: 8306767: Concurrent repacking of extra data in MethodData is potentially unsafe [v19]

[Emanuel Peter]

On Wed, 17 Jan 2024 16:31:38 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

>> They verify that no safepoints happen while holding the lock.  There's a counter in JavaThread.
>> 
>> 
>> #ifdef ASSERT
>>   // Debug support for checking if code allows safepoints or not.
>>   // Safepoints in the VM can happen because of allocation, invoking a VM operation, or blocking on
>>   // mutex, or blocking on an object synchronizer (Java locking).
>>   // If _no_safepoint_count is non-zero, then an assertion failure will happen in any of
>>   // the above cases. The class NoSafepointVerifier is used to set this counter.
>>   int _no_safepoint_count;                             // If 0, thread allow a safepoint to happen
>
> I guess the comment should be updated to say we increment this when taking out a no-safepoint-check mutex.

Ok, I removed the `NoSafepointVerifier`. It seems to work, and pass my verification that we are in a no_safepoint scope.

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PR Review Comment: https://git.openjdk.org/jdk/pull/16840#discussion_r1457668982