RFR 8203174: [Graal] JDI tests fail with Unexpected exception: com.sun.jdi.ObjectCollectedException

[Chris Plummer]

Hi Daniil,

I thought the issue was that C2 was doing metadata allocations, and when 
it ran out of metaspace it did a GC (one that was not triggered by a 
failed object allocation). As a results we were getting objects GCs 
before the test ever got the chance to disable collection on them. I 
thought we also concluded other than this metaspace issue, if the test 
is properly disabling collection on the objects it cared about, it 
shouldn't matter if there are GC's triggered by excessive object 
allocations.

I don't think the following check will always be valid. It may be on by 
default at some point:

  651     public boolean isJVMCICompilerOn() {
  652         String opts = argumentHandler.getLaunchOptions();
  653         return opts.indexOf("-XX:+UseJVMCICompiler") >= 0;
  654     }

thanks,

Chris

On 11/2/18 4:29 PM, Daniil Titov wrote:
> Please review the change that fixes several tests failing with com.sun.jdi.ObjectCollectedException when running with Graal.
>
> There main problem here is that with Graal on JVMCI Compiler threads in the target VM create a lot of objects and sporadically trigger GC that results in the objects created in the target VM in the tests being GCed before the tests complete. The other problem is that for some classes the tests use, e.g. "java.lang.String",  there is already a huge number of instances created by JVMCI threads.
>
> The fix suspends target VM to prevent JVMCI compiler threads from creating new objects during the tests execution. In cases when IOPipe is used for communication between the test and the debuggee the fix suspends all threads but the main rather than suspending the VM. The fix also filters out the checks for some test classes (e.g. "java.lang.String") in cases when the target VM is run with JVMCI compiler options on.
>
> Webrev: http://cr.openjdk.java.net/~dtitov/8203174/webrev.01/
> Bug: https://bugs.openjdk.java.net/browse/JDK-8203174
>
> Thanks,
> Daniil
>
>
>