[jdk21u-dev] Integrated: 8315373: Change VirtualThread to unmount after freezing, re-mount before thawing

[Aleksey Shipilev]

On Thu, 8 Feb 2024 11:17:02 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> This is a series of Loom backports that brings in the fixes from JDK 22 and mainline into JDK 21, where Loom is production-ready. This batch fixes a few thread state and JVMTI problems.
> 
> Unfortunately, these backports are tied together, as they change the same code a few times. It is very hard to make them into separate backports without breaking stuff along the way, so instead I clobbered them together in this PR. They follow the application order from mainline. All patches together touch only the Virtual Thread parts, so the risk for the rest of the code should be minimal.
> 
> Brief explanation of fixes:
> 
> * [JDK-8315373](https://bugs.openjdk.org/browse/JDK-8315373): In mainline since Sep 2023, there is no bug tail. Changes how VTs interact with JVMTI. We want this fix to provide the ground for the rest of backports. Notably, it makes [JDK-8312777](https://bugs.openjdk.org/browse/JDK-8312777) backport clean. 
> * [JDK-8312498](https://bugs.openjdk.org/browse/JDK-8312498): In mainline since Sep 2023. There is a bug tail, [JDK-8322818](https://bugs.openjdk.org/browse/JDK-8322818). Fixes what thread state VT reports when timed-parked. This fixes the actual Loom bug.
> * [JDK-8312777](https://bugs.openjdk.org/browse/JDK-8312777): In mainline since Oct 2023, there is no bug tail. Fixes the JVMTI race with mount/unmount events. Makes [JDK-8322818](https://bugs.openjdk.org/browse/JDK-8322818) backport clean. This fixes the actual Loom bug.
> * [JDK-8321270](https://bugs.openjdk.org/browse/JDK-8321270): In mainline since Dec 2023, there is no bug tail. Makes [JDK-8322818](https://bugs.openjdk.org/browse/JDK-8322818) a clean backport. This fixes the actual Loom performance problem.
> * [JDK-8322818](https://bugs.openjdk.org/browse/JDK-8322818): In mainline since Jan 2023. Fixes the bug introduced by [JDK-8312498](https://bugs.openjdk.org/browse/JDK-8312498). Has two additional follow-ups: [JDK-8323002](https://bugs.openjdk.org/browse/JDK-8323002) and [JDK-8323296](https://bugs.openjdk.org/browse/JDK-8323296).
> * [JDK-8323002](https://bugs.openjdk.org/browse/JDK-8323002): In mainline since Jan 2023. Follow-up test fix for [JDK-8322818](https://bugs.openjdk.org/browse/JDK-8322818). Test-only change.
> * [JDK-8323296](https://bugs.openjdk.org/browse/JDK-8323296): In mainline since Jan 2023. Follow-up test fix for [JDK-8322818](https://bugs.openjdk.org/browse/JDK-8322818). Test-only change.
> * [JDK-8316924](https://bugs.openjdk.org/browse/JDK-8316924): In mainline since Sep 2023. Fo...

This pull request has now been integrated.

Changeset: 3eb5517b
Author:    Aleksey Shipilev <shade at openjdk.org>
URL:       https://git.openjdk.org/jdk21u-dev/commit/3eb5517b73b58bee4985ae6c20a6e613e35d426c
Stats:     1194 lines in 13 files changed: 909 ins; 92 del; 193 mod

8315373: Change VirtualThread to unmount after freezing, re-mount before thawing
8312498: Thread::getState and JVM TI GetThreadState should return TIMED_WAITING virtual thread is timed parked
8312777: notifyJvmtiMount before notifyJvmtiUnmount
8321270: Virtual Thread.yield consumes parking permit
8322818: Thread::getStackTrace can fail with InternalError if virtual thread is timed-parked when pinned
8323002: test/jdk/java/lang/Thread/virtual/stress/GetStackTraceALotWhenPinned.java times out on macosx-x64
8323296: java/lang/Thread/virtual/stress/GetStackTraceALotWhenPinned.java#id1 timed out
8316924: java/lang/Thread/virtual/stress/ParkALot.java times out

Backport-of: 9a83d55887e5e3a0a2e1e020c6ccb91604672358

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PR: https://git.openjdk.org/jdk21u-dev/pull/245