I’m afraid this change requires changes in the Serviceability Agent as well. See OopUtilities.threadOopGetName() for example.
/Staffan > On 10 nov 2014, at 15:19, Aleksey Shipilev <aleksey.shipi...@oracle.com> > wrote: > > Hi David, Chris, > > On 11/10/2014 04:53 PM, Chris Hegarty wrote: >> On 10/11/14 12:56, David Holmes wrote: >>> On 10/11/2014 9:52 PM, Chris Hegarty wrote: >>>> I have only looked at the libraries changes, and I think they make sense >>>> . As in, I can find no reason why the name cannot be changed to be a >>>> String. >>> >>> Very quick response, but IIRC this has been examined in the past and >>> there were reasons why it can't/shouldn't be done. Will try to dig out >>> more details in the morning. >> >> If there was previous discussion on this, that revealed some substantial >> issue, that would be great, but I can't recall, or find, it now. >> >> Hotspot express, and the desire for hotspot to run with different >> library versions, would certainly cause complication, but I don't >> believe that is an issue now. >> >> Just on that, the library changes are minimal, and if this were to >> proceed then they can accompany the hotspot change, as they make their >> way into jdk9/dev. >> >> Anyway, this should await your reply. > > Alan was having the same concern, there is an issue with JNI/JVMTI and > other power users that might break when exposed to under-constructed > Thread, e.g: > https://bugs.openjdk.java.net/browse/JDK-6412693 > > This is why I ran jvmti and serviceability tests for this change, > yielding no failures. This reinforces my belief this patch does not > break the important invariant: if there is a problem with "Thread.name = > name.toCharArray()" anywhere in Thread code, then "Thread.name = name" > does neither regress it further nor fixes it. > > Then I speculated that having char[] name would help VM initialize the > name if we wanted to switch to complete VM-side initialization of > Thread, but it seems we can do String oop instantiation in the similar vein. > > Caching the name feels like a band-aid, that will probably complicate > the Thread initialization on VM side even more. Let's wait and see if > David can come up with some horror issue we are overlooking. :) > > Thanks, > -Aleksey. >
