RFR: Disable LeakProfiler for Shenandoah

[Roman Kennke]

Ok for now. Gotta fix this for real (but upstream).

Roman

> Shenandoah crashes while processing weak references in LeakProfiler, may
> be for the same reason as ZGC(?)
> (https://bugs.openjdk.java.net/browse/JDK-8205338)
> 
> Disable it for Shenandoah as well.
> 
> 
> diff -r 09d6d46d1f66 src/hotspot/share/jfr/leakprofiler/leakProfiler.cpp
> --- a/src/hotspot/share/jfr/leakprofiler/leakProfiler.cpp       Wed Jun
> 20 16:48:56 2018 -0400
> +++ b/src/hotspot/share/jfr/leakprofiler/leakProfiler.cpp       Wed Jun
> 20 17:57:57 2018 -0400
> @@ -42,6 +42,11 @@
> 
>  static volatile jbyte suspended = 0;
>  bool LeakProfiler::start(jint sample_count) {
> +   if (UseShenandoahGC) {
> +    log_warning(jfr)("LeakProfiler is currently not supported in
> combination with Shenandoah GC");
> +    return false;
> +  }
> +
>    if (_object_sampler != NULL) {
>      // already started
>      return true;
> 
> 
> Ok?
> 
> Thanks,
> 
> -Zhengyu
>