Integrated: 8346123: [REDO] NMT should not use ThreadCritical

[Robert Toyonaga]

On Fri, 13 Dec 2024 21:29:53 GMT, Robert Toyonaga <duke at openjdk.org> wrote:

> This is a redo of [JDK-8304824](https://bugs.openjdk.org/browse/JDK-8304824) which was backed out by [JDK-8343726](https://bugs.openjdk.org/browse/JDK-8343726) due to problems documented in [JDK-8343244](https://bugs.openjdk.org/browse/JDK-8343244).
> 
> The problem was that `NmtVirtualMemoryLocker` was not locking when the current thread is not attached by checking `Thread::current_or_null_safe() != nullptr`. This is necessary during VM init, but should not be allowed afterward. NMT may be used in `attach_current_thread` before the current thread is set. The lock was not being acquired in that case, which intermittently caused NMT accounting to become corrupted, triggering various assertions when future NMT operations are done.  To fix this, I've adopted [Thomas' suggestion](https://github.com/openjdk/jdk/pull/21928#issuecomment-2460238057) to reverse the order of 
> 
> 
> thread->register_thread_stack_with_NMT();
> thread->initialize_thread_current();
> 
> 
> in `attach_current_thread`.  This allows `NmtVirtualMemoryLocker` to be locked after current thread is set. 
> 
> To allow for `NmtVirtualMemoryLocker` to be used during VM init, I've replaced the `ConditionalMutexLocker` check `Thread::current_or_null_safe() != nullptr` with a new flag: `_done_bootstrap`. This flag prevents the lock from being used during VM init, at which point we are single threaded anyway. This avoids errors due to Hotspot mutexes and current thread not yet being ready. 
> 
> I also added new asserts in `virtualMemoryTracker.cpp` to catch future bugs like this where the lock is not held when it should be. I updated the appropriate VMT tests to also lock (there were a few cases where locking was being bypassed) so they can pass the new asserts.
> 
> I also removed the unused `_query_lock` variable in `MemTracker`.
> 
> Testing: 
> 
> - On Linux amd64, I was able to consistently reproduce the errors described in [JDK-8343244](https://bugs.openjdk.org/browse/JDK-8343244) by increasing the number of test threads in `java/lang/Thread/jni/AttachCurrentThread/AttachTest.java`. The test consistently passes with the new changes in this PR.
> - hotspot_nmt , gtest:VirtualSpace, tier1

This pull request has now been integrated.

Changeset: 3804082c
Author:    Robert Toyonaga <rtoyonag at redhat.com>
Committer: Thomas Stuefe <stuefe at openjdk.org>
URL:       https://git.openjdk.org/jdk/commit/3804082cba56e6d26c500880cc5cbe6d4332d8f8
Stats:     124 lines in 19 files changed: 75 ins; 28 del; 21 mod

8346123: [REDO] NMT should not use ThreadCritical

Reviewed-by: dholmes, coleenp, stuefe

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PR: https://git.openjdk.org/jdk/pull/22745