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8305425: Thread.isAlive0 doesn't need to call into the VM

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Co-authored-by: Aleksey Shipilev <shade@openjdk.org>
Reviewed-by: shade, coleenp, alanb
This commit is contained in:
David Holmes 2023-04-05 21:54:38 +00:00
parent b5d204c3a4
commit 35cb303a2c
7 changed files with 130 additions and 19 deletions
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16
src/java.base/share/classes/java/lang/Thread.java
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@ -1,5 +1,5 @@
/*
* Copyright (c) 1994, 2022, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 1994, 2023, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
@ -226,8 +226,15 @@ public class Thread implements Runnable {
registerNatives();
}
/* Reserved for exclusive use by the JVM, maybe move to FieldHolder */
private long eetop;
/*
* Reserved for exclusive use by the JVM. Cannot be moved to the FieldHolder
* as it needs to be set by the VM for JNI attaching threads, before executing
* the constructor that will create the FieldHolder. The historically named
* `eetop` holds the address of the underlying VM JavaThread, and is set to
* non-zero when the thread is started, and reset to zero when the thread terminates.
* A non-zero value indicates this thread isAlive().
*/
private volatile long eetop;
// thread id
private final long tid;
@ -1840,9 +1847,8 @@ public class Thread implements Runnable {
* This method is non-final so it can be overridden.
*/
boolean alive() {
return isAlive0();
return eetop != 0;
}
private native boolean isAlive0();
/**
* Throws {@code UnsupportedOperationException}.