Withdrawn: 8277486: NMT: Cleanup ThreadStackTracker

[Zhengyu Gu]

On Mon, 22 Nov 2021 15:36:41 GMT, Zhengyu Gu <zgu at openjdk.org> wrote:

> There are several issues with `ThreadStackTracker`.
> 
> 1) Following assertion:
>   `assert(MemTracker::tracking_level() >= NMT_summary, "Must be");`
> in `ThreadStackTracker::record/release_thread_stack()` is unreliable. The full fence after downgrading tracking level is *not* sufficient to avoid the racy.
> 
> 2) NMT tracking level is downgraded without `ThreadCritical` lock held. But, it does require `ThreadCritical` lock to be held when it actually downgrade internal tracking data structure, so checking internal state is reliable to determine current tracking state.
> Add assertion to ensure correct tracking state
> 
> 3) `_thread_counter` is updated with `ThreadCritical` lock, but is read without the lock. Change to atomic update to ensure reader will not read stale value.
> 
> 4) NMT events are relative rare. So far, I have yet seen (1) assertion failure but add new test may help to spot such problem.

This pull request has been closed without being integrated.

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PR: https://git.openjdk.java.net/jdk/pull/6504