JDK-8199735 : Mark word updates need to use Access API
  • Type: Enhancement
  • Component: hotspot
  • Sub-Component: gc
  • Priority: P4
  • Status: Resolved
  • Resolution: Fixed
  • Submitted: 2018-03-16
  • Updated: 2021-08-18
  • Resolved: 2018-04-09
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JDK 11
11 b10Fixed
Related Reports
Relates :  
JDK-8272654 - Mark word accesses should not use Access API
Relates :  
JDK-8251358 - Clean up Access configuration after Shenandoah barrier change
Relates :  
JDK-8064885 - Remove oopDesc inheritance relation from markOopDesc
Description
Currently, the mark word is accessed directly in oopDesc::mark() set_mark() and a bunch of other accessors. Those need to use the Access API instead because GC might want to employ barriers on those accesses, pretty much like every other field in oopDesc.
Comments
URL: http://hg.openjdk.java.net/jdk/jdk/rev/a47d1e21b3f1 User: jwilhelm Date: 2018-04-17 16:01:04 +0000
17-04-2018
URL: http://hg.openjdk.java.net/jdk/hs/rev/a47d1e21b3f1 User: eosterlund Date: 2018-04-09 12:36:32 +0000
09-04-2018
No, you misunderstood. The header itself is kindof like just another field in oop. Accessing it should go through Access. I've got a patch which should illustrate it. Stay tuned :-)
19-03-2018
markOop is not an oop, so I am not sure it needs any barriers. It is just the word in the header of an oop. Every time you use the markOop as an oop you are very likely to have done something wrong. See also JDK-8064885 for more information.
19-03-2018