P4
This is a regression from JDK-8315884.
When using `+UseObjectMonitorTable` monitors are inflated in a locked state effectively blocking out deflation. `LightweightSynchronizer::enter_for` assumed this to be true. But when the `-UseObjectMonitorTable` path was added `// Do the old inflate and enter.` this is no longer true as it first inflates a monitor in an unlocked state and then tries to lock. We need to introduce a retry loop similar to what was used beforeJDK-8315884.
I propose we add this retry loop for both cases, to decouple the `LightweightSynchronizer::enter_for` from how lock elimination is done. With a retry loop, the only requirements for using `LightweightSynchronizer::enter_for` is that the Object locked on cannot have been locked on by another thread, i.e. there is no contention, but makes no assumptions on the interaction with the deflation thread.
When using `+UseObjectMonitorTable` monitors are inflated in a locked state effectively blocking out deflation. `LightweightSynchronizer::enter_for` assumed this to be true. But when the `-UseObjectMonitorTable` path was added `// Do the old inflate and enter.` this is no longer true as it first inflates a monitor in an unlocked state and then tries to lock. We need to introduce a retry loop similar to what was used before
I propose we add this retry loop for both cases, to decouple the `LightweightSynchronizer::enter_for` from how lock elimination is done. With a retry loop, the only requirements for using `LightweightSynchronizer::enter_for` is that the Object locked on cannot have been locked on by another thread, i.e. there is no contention, but makes no assumptions on the interaction with the deflation thread.
- links to
-
Commit(master)
openjdk/jdk/6fad6af0
-
Review(master)
openjdk/jdk/21420