Recently [JDK-8305511](https://bugs.openjdk.org/browse/JDK-8305511) removed the
"@ignore 6951287 ", allowing this test to run, which is why this failure mode
is now turning up.
There is a race condition, leading to the `popFrames()` call being done while a
native method is in the set of frames to be popped. This results in a
`NativeMethodException` instead of the frames being popped. The debuggee has:
public static void waiter() {
if (waiting) {
return;
}
waiting = true;
System.out.println(" debuggee: in waiter");
while (true) {
}
}
And the debugger waits for `waiting == true` (checked via JDI calls) before
suspending and doing the `popFrames()`. The problem is the println() after
setting `waiting = true`. The debugger side can detect that `waiting == true`
before the println() is complete, and the println() involves native code. Once
`waiting` is set true, we need to make sure no other method calls are made so
we can be sure that only the `waiter()` method is on the stack.
Note there is a lot of interesting history to this CR, including
[JDK-6417053](https://bugs.openjdk.org/browse/JDK-6417053), which actually
reproduced this issue long ago (but got closed as CNR), although it failed with
a different error message (even though it was the same issue), and the
different error message was itself the result of another bug that was
inadvertently fixed when virtual threads support was added to JDI. See the CR
for details if you are interested.
-------------
Commit messages:
- Move println to before setting the waiting flag
Changes: https://git.openjdk.org/jdk/pull/13657/files
Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13657&range=00
Issue: https://bugs.openjdk.org/browse/JDK-8306705
Stats: 3 lines in 1 file changed: 2 ins; 1 del; 0 mod
Patch: https://git.openjdk.org/jdk/pull/13657.diff
Fetch: git fetch https://git.openjdk.org/jdk.git pull/13657/head:pull/13657
PR: https://git.openjdk.org/jdk/pull/13657
