RFR 8252249: nsk/stress/stack/stack016.java fails with "Error: TEST_BUG: trickyRecursion() must throw an error anyway!"

[David Holmes]

Hi Harold,

On 2/09/2020 5:02 am, Harold Seigel wrote:
> Hi,
> 
> Please review this change to hotspot test 
> vmTestbase/nsk/stress/stack/stack016.java.  The test calls a recursive 
> method and keeps track of the number of repetitions needed to cause an 
> exception.  It then runs a bunch of threads that call the recursive 
> method for a multiple of the repetition number, expecting each of them 
> to get a StackOverflowError or OutOfMemoryError exception. Occasionally, 
> the test fails because one of the threads does not throw an exception.
> 
> This change tries to fix this in two ways.  One, by making sure that the 
> thread used to determine the number of repetitions gets a 
> StackOverflowError or OutOfMemoryError exception, and not some other 
> unexpected exception. 

That's a good improvement, though other exceptions seem unlikely - have 
you actually observed any unexpected exceptions?

> The other way is to run the test twice, once with 
> -Xcomp and once with -Xint, to ensure that thread stack consumption 
> doesn't vary because the original thread called an interpreted method 
> and a subsequent thread called a compiled method.

Right - running interpreted would give a different maximum recursion 
depth from running under the JIT, and when we bumped up the stack depth 
we would have run far more iterations and so JIT'd more code - thus 
breaking the test. So forcing fully interpreted or fully compiled seems 
a good way to stabilise things.

But I would suggest that you keep the required condition

vm.compMode != "Xcomp"

to minimise the runs of this test. When executed as part of an Xcomp run 
both @run's will behave exactly the same way (Xcomp) - and that is the 
same as the second @run in a non-Xcomp run. So no point running the 
Xcomp version three times.

Thanks,
David
-----

> 
> Open Webrev: 
> http://cr.openjdk.java.net/~hseigel/bug_8252249.stack/webrev/index.html
> 
> JBS Bug: https://bugs.openjdk.java.net/browse/JDK-8252249
> 
> The modified test was tested on Mac OS, Linux x64, and Windows.
> 
> Thanks, Harold
>