JDK-7092412 : G1: Some roots not marked during an initial mark that gets an evacuation failure
  • Type: Bug
  • Component: hotspot
  • Sub-Component: gc
  • Affected Version: 7u2
  • Priority: P3
  • Status: Closed
  • Resolution: Fixed
  • OS: generic
  • CPU: generic
  • Submitted: 2011-09-19
  • Updated: 2012-12-05
  • Resolved: 2012-01-23
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JDK 7 JDK 8 Other
7u2Fixed 8Fixed hs22Fixed
Related Reports
Relates :  
JDK-7080389 - G1: refactor marking code in evacuation pause copy closures
Description
While investigating the issues described in 7086533 and 7086538, marking verification has identified some missing marks:

[GC remark
 VerifyDuringGC:(before)[Verifying threads Roots (excluding permgen) Permgen roots HeapRegionSets HeapRegions RemSet syms strs zone dict hand C-heap code cache ]
 VerifyDuringGC:(after)[Verifying threads Roots (excluding permgen)

Root location 0x0072f3f4 points to dead obj 0x099da910
nsk.share.gc.LinkedMemoryObject 
 - klass: 'nsk/share/gc/LinkedMemoryObject'
 - ---- fields (total size 6 words):
 - private 'storage' '[B' @8  [B (99fce38)
 - private 'next' 'Lnsk/share/gc/LinkedMemoryObject;' @12  a 'nsk/share/gc/LinkedMemoryObject' (99da8f8)
 - private 'prev' 'Lnsk/share/gc/LinkedMemoryObject;' @16  NULL

Root location 0x0072f3fc points to dead obj 0x099ff548
nsk.share.gc.LinkedMemoryObject 
 - klass: 'nsk/share/gc/LinkedMemoryObject'
 - ---- fields (total size 6 words):
 - private 'storage' '[B' @8  NULL
 - private 'next' 'Lnsk/share/gc/LinkedMemoryObject;' @12  NULL
 - private 'prev' 'Lnsk/share/gc/LinkedMemoryObject;' @16  NULL
Comments
EVALUATION See main CR
22-10-2011
EVALUATION Not able to find behaviour changes,
18-10-2011
EVALUATION http://hg.openjdk.java.net/hsx/hsx22/hotspot/rev/66db4a2fc13c
12-10-2011
EVALUATION http://hg.openjdk.java.net/hsx/hotspot-gc/hotspot/rev/663cb89032b1
21-09-2011
SUGGESTED FIX In the evacuation failure handling code; when a root object is successfuly forwarded to itself - mark the root object.
19-09-2011
EVALUATION Some root objects not being marked during an initial mark pause that gets an evacuation failure.
19-09-2011