Request for review (S): add the JRE name to the error log

[Christian Thalinger]

On May 16, 2012, at 12:44 PM, Krystal Mok wrote:

> Hi all,
> 
> Could I get some review for this change, please?
> https://gist.github.com/2709918#file_jre_name.patch
> I'm considering this as an initial draft version, and will improve it later on
> based on comments received.
> 
> Background:
> 
> An earlier case on hotspot-dev [1][2] seemed to have hit a bug caused by mix-
> matching an Oracle JRE with a OpenJDK-based HotSpot VM.
> 
> Chris suggested [3] that, to better aid future analysis of similar problems,
> it's useful to print the JRE name in the error log, in addition to the JRE
> version as printed currently. This patch implements Chris' suggestion.
> 
> An example of the effect of this patch is avaiable [4].
> 
> There are a few details that I'm not too sure about yet, and I'm looking for
> comments on them:
> 
> 1. How and when should I get the JRE name?
> 
> The JRE name is only exposed as a field of a Java-level class, namely the
> "java_runtime_name" constant field in sun.misc.Version. I couldn't find it
> exposed anywhere else. It is set into the Java-level system properties, by the
> key "java.runtime.name", but that's not immediately available to the VM side.
> 
> In my patch, I'm fetching the JRE name from sun.misc.Version.java_runtime_name
> immediately after java.lang.System.initializeSystemClass() is invoked, and then
> storing it in a static field in JDK_Version. This is safer to do then fetching
> the name during error reporting, because it may be unreliable to access Java
> heap contents when the VM is crashing.
> 
> There are other alternatives that I've thought about. One is adding a new
> private interface between JDK/JVM that would allow the JDK to expose its name
> to the VM directly, perhaps with a new function JDK_GetName0(). But this is
> more involved then the proposed change.
> 
> 2. Where should I store the JRE name?
> 
> As mentioned, I'm storing it in a newly added static field in JDK_Version right
> now. But I'm not sure if this is the place it belongs. Universe doesn't seem
> like the right place, neither.
> 
> Any suggestions or comments are welcomed.

I looked at the changes and I think this is the right way to implement it.  It will definitely help debugging some strange crashes like the one mentioned.

-- Chris

> 
> Should I cc serviceability-dev as well?
> 
> Regards,
> Kris
> 
> [1]: http://mail.openjdk.java.net/pipermail/hotspot-compiler-dev/2012-May/007647.html
> [2]: http://mail.openjdk.java.net/pipermail/hotspot-dev/2012-May/005711.html
> [3]: http://mail.openjdk.java.net/pipermail/hotspot-dev/2012-May/005725.html
> [4]: https://gist.github.com/2709918

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