JDK-6774607 : SIGSEGV or (!is_null(v),"oop value can never be zero") assertion when running with CMS and COOPs
  • Type: Bug
  • Component: hotspot
  • Sub-Component: gc
  • Affected Version: hs14
  • Priority: P2
  • Status: Resolved
  • Resolution: Fixed
  • OS: solaris
  • CPU: x86
  • Submitted: 2008-11-21
  • Updated: 2010-12-07
  • Resolved: 2009-03-20
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JDK 6 JDK 7 Other
6u14Fixed 7Fixed hs14Fixed
Related Reports
Relates :  
JDK-6819891 - ParNew: Fix work queue overflow code to deal correctly with +UseCompressedOops
Description
"-XX:+UseConcMarkSweepGC -XX:+UseCompressedOops" leads product jvm to fail with SIGSEGV
and fastdebug jvm to fail with following assertion:
 #  Internal Error (/BUILD_AREA/jdk7.0/hotspot/src/share/vm/oops/oop.inline.hpp:150), pid=29365, tid=3
 #  Error: assert(!is_null(v),"oop value can never be zero")
Comments
EVALUATION The fix for this CR is being done under 6819891. This bug will be closed as a duplicate of 6819891 once the latter is fixed. See 6819891 for more details.
19-03-2009
WORK AROUND -XX:-UseParNewGC or -XX:-UseCompressedOops
19-03-2009
EVALUATION It turns out that the fix I made here is insufficient for the case of compressed oops if there is work queue overflow in ParNew involving an object array. That needs to be fixed by changing the overflow handling code to user a compressed pointer (i.e. narrow oop) to point to the next object in the overflow list. This is probably somewhat of a showstopper for CompressedOops and CMS because it can cause GC crashes. The only reliable workaround is to disable ParNew in such cases (although, following 6787254, this is unlikely to affect most casual users, it cab still affect users who make use of very large heaps and have very large object arrays such as hashtables).
19-03-2009
SUGGESTED FIX changeset: 445:df4305d4c1a1 user: ysr date: Mon Nov 24 09:53:31 2008 -0800 files: src/share/vm/gc_implementation/parNew/parNewGeneration.cpp src/share/vm/oops/oop.inline.hpp description: 6774607: SIGSEGV or (!is_null(v),"oop value can never be zero") assertion when running with CMS and COOPs Summary: Use the more permissive set_klass_or_null() and klass_or_null() interfaces in ParNew's workqueue overflow code that manipulates the klass-word. Reviewed-by: coleenp diff -r c96030fff130 -r df4305d4c1a1 src/share/vm/gc_implementation/parNew/parNewGeneration.cpp --- a/src/share/vm/gc_implementation/parNew/parNewGeneration.cpp Thu Nov 20 16:56:09 2008 -0800 +++ b/src/share/vm/gc_implementation/parNew/parNewGeneration.cpp Mon Nov 24 09:53:31 2008 -0800 @@ -1205,7 +1205,7 @@ ParNewGeneration::take_from_overflow_lis int n = 0; while (cur != NULL) { oop obj_to_push = cur->forwardee(); - oop next = oop(cur->klass()); + oop next = oop(cur->klass_or_null()); cur->set_klass(obj_to_push->klass()); if (par_scan_state->should_be_partially_scanned(obj_to_push, cur)) { obj_to_push = cur; diff -r c96030fff130 -r df4305d4c1a1 src/share/vm/oops/oop.inline.hpp --- a/src/share/vm/oops/oop.inline.hpp Thu Nov 20 16:56:09 2008 -0800 +++ b/src/share/vm/oops/oop.inline.hpp Mon Nov 24 09:53:31 2008 -0800 @@ -92,7 +92,7 @@ inline void oopDesc::set_klass_to_list_p // This is only to be used during GC, for from-space objects, so no // barrier is needed. if (UseCompressedOops) { - _metadata._compressed_klass = encode_heap_oop_not_null(k); + _metadata._compressed_klass = encode_heap_oop(k); // may be null (parnew overflow handling) } else { _metadata._klass = (klassOop)k; }
02-12-2008
SUGGESTED FIX > 6774607 SIGSEGV or (!is_null(v),"oop value can never be zero") > assertion when running with CMS and COOPs > > ParNew's work queue overflow handling uses the klass-word of > the original (Eden or from-space) copy of an object to link > overflown oops into the overflow list, so we need to call > the more permissive methods (which permit a null value) > in the overflow handling code that manipulates this field. > > Testing: the tests listed in the bug report > webrev: http://analemma.sfbay.sun.com/net/neeraja/export/ysr/soft-ref/webrev/
02-12-2008
EVALUATION > 6774607 SIGSEGV or (!is_null(v),"oop value can never be zero") > assertion when running with CMS and COOPs > > ParNew's work queue overflow handling uses the klass-word of > the original (Eden or from-space) copy of an object to link > overflown oops into the overflow list, so we need to call > the more permissive methods (which permit a null value) > in the overflow handling code that manipulates this field. > > Testing: the tests listed in the bug report > webrev: http://analemma.sfbay.sun.com/net/neeraja/export/ysr/soft-ref/webrev/
02-12-2008
EVALUATION http://hg.openjdk.java.net/jdk7/hotspot-gc/hotspot/rev/df4305d4c1a1
24-11-2008