RFR(XS): G1: Concurrent mark stuck in loop calling os::elapsedVTime()

[Thomas Schatzl]

Hi,

On Wed, 2014-04-30 at 15:13 +0200, Per Liden wrote:
> Hi,
> 
> Here's another G1 concurrent mark fix I'd like to have reviewed.
> 
> Summary: If the heap is expended when a concurrent mark is in progress 
> there's a window where the global marking finger (_cm->_finger) points 
> past the heap end (_cm->_heap_end). When this happens the marking 
> threads will get stuck in a loop spinning, because _cm->out_of_regions() 
> will still return false. out_of_regions() is currently implemented as 
> "return _finger == _heap_end;".
> 
> This patch fixes this problem by adjusting out_of_region() to instead be 
> "return _finger >= _heap_end;". This is safe because objects in those 
> new regions will be considered live anyway, because their TAMS will be 
> equal to bottom.
> 
> Bug: https://bugs.openjdk.java.net/browse/JDK-8040804
> Webrev: http://cr.openjdk.java.net/~pliden/8040804/webrev.0/
> 

  Looks good.

Thomas