I saw the following crash when I run product build jdk6U1 b05 on ATG app with CMS gc. It happened after running for about 35 hours, but I couldn't reproduce it since then.

Here is Ramki's comment regarding the crash:
some of the code related to these methods was indeed
touched somewhat recently in relation to CR 6459113, which was
recently backported to 6u1. [FWIW, the same changes are present
in 7.0, 5u10 and 1.4.2_14 as well.]

The webrev for this set of changes in 6u1 can be found here:

http://analemma.sfbay.sun.com/net/prt-archiver.sfbay/data/archived_workspaces/1.6/update1/baseline/2006/20061121150426.ysr.6u1/workspace/webrevs/webrev-2006.11.21/index

In particular look at the changes in compactibleFreeListSpace.cpp.

Testing information:
--------------------
hostname: jtg-i119.sfbay.sun.com (it is a hyperthread enabled machine)
platform:
SunOS jtg-i119 5.10 Generic_118855-36 i86pc i386 i86pc
VM option: "-server -XX:+UseConcMarkSweepGC"

log/core file location: /bt/atgrun.6807.-server
-rw-r--r-- 1 root root 7422998 Mar 15 00:03 atgserver.log
-rw-r--r-- 1 root root 205737145 Mar 16 11:02 core.8343

bash-3.00# tail atgserver.log
Unexpected Error
------------------------------------------------------------------------------
SIGSEGV (0xb) at pc=0xd0a3a777, pid=8343, tid=6

Do you want to debug the problem?

To debug, run 'dbx - 8343'; then switch to thread 6
Enter 'yes' to launch dbx automatically (PATH must include dbx)
Otherwise, press RETURN to abort...

(dbx) where
current thread: t@6
=>[1] ___nanosleep(0xcd298c58, 0xcd298c60), at 0xd0f303d5
[2] _sleep(0x64), at 0xd0f24a33
[3] os::message_box(0xd0d93f99, 0xd0e21900), at 0xd0c42ace
[4] VMError::show_message_box(0xcd298f14, 0xd0e21900, 0x7d0), at 0xd0cd2f3d
[5] VMError::report_and_die(0xcd298f14), at 0xd0cd29bf
[6] JVM_handle_solaris_signal(0xb, 0xcd299234, 0xcd299034, 0x1), at 0xd08f1704
[7] signalHandler(0xb, 0xcd299234, 0xcd299034), at 0xd08f0fce
[8] __sighndlr(0xb, 0xcd299234, 0xcd299034, 0xd08f0fa8), at 0xd0f3014f
---- called from signal handler with signal 11 (SIGSEGV) ------
[9] TreeList::removeChunkReplaceIfNeeded(0x200023, 0xc54d49c0), at 0xd0a3a777
[10] BinaryTreeDictionary::removeChunkFromTree(0x8076950, 0xc54d49c0), at 0xd0a3ac8f
[11] BinaryTreeDictionary::getChunkFromTree(0x8076950, 0x100, 0x0, 0x0), at 0xd0a3abae
[12] BinaryTreeDictionary::getChunk(0x8076950, 0x100, 0x0), at 0xd0a3c0fa
[13] CompactibleFreeListSpace::par_get_chunk_of_blocks(0x80bac10, 0x10, 0x10, 0x80c541c), at 0xd0a6ff78
[14] CFLS_LAB::alloc(0x80c4e58, 0x10), at 0xd0a6fb6a
[15] ConcurrentMarkSweepGeneration::par_promote(0x80bab08, 0x0, 0xc1e988c8, 0x21, 0x10), at 0xd0a7b24d
[16] ParNewGeneration::copy_to_survivor_space_avoiding_promotion_undo(0x8078ed8, 0xcd299ae0, 0xc1e988c8, 0x10, 0x21, 0x0), at 0xd0c4a3fb
[17] ParScanClosure::do_oop_work(0xcd299c6c, 0xc5426168, 0x1, 0x0, 0x0), at 0xd0acf52f
[18] instanceKlass::oop_oop_iterate_nv(0xc900c730, 0xc5426160, 0xcd299c6c), at 0xd0acb4f9
[19] ParScanThreadState::trim_queues(0xcd299ae0, 0x28), at 0xd0c48f0d
[20] ParScanClosure::do_oop_work(0xcd299cb4, 0xc3c61bac, 0x1, 0x1, 0x0), at 0xd0acf552
[21] ParRootScanWithBarrierTwoGensClosure::do_oop(0xcd299cb4, 0xc3c61bac), at 0xd0c4add6
[22] objArrayKlass::oop_oop_iterate_nv_m(0xc908e650, 0xc3c5f590, 0xcd2996e0, 0xcd299638), at 0xd0c3cc68
[23] FreeListSpace_DCTOC::walk_mem_region_with_cl_par(0x80787a8, 0xcd299690, 0xc3c5f590, 0xc3c61e00, 0xcd2996e0), at 0xd0a6c057
[24] FreeListSpace_DCTOC::walk_mem_region_with_cl(0x80787a8, 0xcd2996d0, 0xc3c5f590, 0xc3c61e00, 0xcd2996e0), at 0xd0a6bf1f
[25] Filtering_DCTOC::walk_mem_region(0x80787a8, 0xcd299738, 0xc3c5f590, 0xc3c61e00), at 0xd0c8206b
[26] DirtyCardToOopClosure::do_MemRegion(0x80787a8, 0xcd299778), at 0xd0c81ea9
[27] ClearNoncleanCardWrapper::do_MemRegion(0xcd2999c0, 0xcd2997e8), at 0xd0a43925
[28] CardTableModRefBS::non_clean_card_iterate_work(0x8078e78, 0xcd299868, 0xcd2999c0, 0x0), at 0xd0a42293
[29] CardTableModRefBS::process_stride(0x8078e78, 0x80bac10, 0xcd2998f8, 0x3, 0x8, 0x80787a8, 0xcd2999c0, 0x0, 0x82da598, 0xcd1ff0, 0x1c5), at 0xd0a42974
[30] CardTableModRefBS::par_non_clean_card_iterate_work(0x8078e78, 0x80bac10, 0xcd299960, 0x80787a8, 0xcd2999c0, 0x0, 0x4), at 0xd0a42390
[31] CardTableModRefBS::non_clean_card_iterate(0x8078e78, 0x80bac10, 0xcd2999b8, 0x80787a8, 0xcd2999c0, 0x0), at 0xd0a41fb7
[32] CardTableRS::younger_refs_in_space_iterate(0x8078e70, 0x80bac10, 0xcd299cb4), at 0xd0a430a5
[33] Generation::younger_refs_in_space_iterate(0x80bab08, 0x80bac10, 0xcd299cb4), at 0xd0abdc15
[34] ConcurrentMarkSweepGeneration::younger_refs_iterate(0x80bab08, 0xcd299cb4), at 0xd0a7dd91
[35] CardTableRS::younger_refs_iterate(0x8078e70, 0x80bab08, 0xcd299cb4), at 0xd0a42fa4
[36] GenCollectedHeap::gen_process_strong_roots(0x8074208, 0x0, 0x1, 0x0, 0x1, 0xcd299cb4, 0xcd299c90), at 0xd0ab7b4d
[37] ParNewGenTask::work(0xcd1329bc, 0x0), at 0xd0c49560
[38] GangWorker::loop(0x8078000), at 0xd0cd6504
[39] GangWorker::run(0x8078000), at 0xd0cd63ef
[40] java_start(0x8078000), at 0xd0c403eb
[41] _thr_setup(0xcd320c00), at 0xd0f2fd46
[42] _lwp_start(), at 0xd0f30030
In view of the recently reported crashes with this signature seen
with some frequency on 6u11 and with greater frequency on 6u16,
where the customer was using a fixed size heap, the conjecture
in the display above, linking this to the changeset for 6459113,
is incorrect and is a different issue.

Customer will be checking if:
(1) problem reproduces with 6u16 with -XX:-UseParNewGC, and
(2) problem reproduces with hs17 jvm