I have been unable to collect a core using linux-crashdump on my physical machines, it doesn't seem dump it and reboot automatically. However it does seem to load the crash kernel (kdump init script).

I did collect another stack trace from one of my EC2 machines:

[2498228.006101] divide error: 0000 [#1] SMP 
[2498228.006113] last sysfs file: /sys/devices/xen/vbd-16756/block/sdx4/stat
[2498228.006117] CPU 0 
[2498228.006120] Modules linked in: btrfs zlib_deflate crc32c libcrc32c ufs qnx4 hfsplus hfs minix ntfs vfat msdos fat raid0 ipt_REJECT ipt_LOG xt_limit xt_tcpudp ipt_addrtype xt_state ip6table_filter ip6_tables ipv6 md_mod nf_nat_irc nf_conntrack_irc nf_nat_ftp nf_nat nf_conntrack_ipv4 nf_defrag_ipv4 nf_conntrack_ftp nf_conntrack iptable_filter ip_tables x_tables
[2498228.006157] Pid: 2128, comm: beam.smp Not tainted 2.6.32-305-ec2 #9-Ubuntu 
[2498228.006161] RIP: e030:[<ffffffff8102ceb4>]  [<ffffffff8102ceb4>] update_sd_lb_stats+0x3a4/0x4e0
[2498228.006172] RSP: e02b:ffff88044188f9f8  EFLAGS: 00010046
[2498228.006176] RAX: 0000000000000000 RBX: ffff88044188fbe4 RCX: 0000000000000001
[2498228.006179] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
[2498228.006183] RBP: ffff88044188fad8 R08: ffff88000184dbc8 R09: 0000000000000040
[2498228.006187] R10: 0000000000000000 R11: 0000000000000000 R12: 00000000ffffffff
[2498228.006191] R13: 000000000000a380 R14: ffffffffffffffff R15: 0000000000000000
[2498228.006199] FS:  00007fd37084f710(0000) GS:ffff880001846000(0000) knlGS:0000000000000000
[2498228.006204] CS:  e033 DS: 0000 ES: 0000 CR0: 000000008005003b
[2498228.006207] CR2: 00007fd35e7bd000 CR3: 0000000440f9b000 CR4: 0000000000002620
[2498228.006211] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[2498228.006215] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000000
[2498228.006220] Process beam.smp (pid: 2128, threadinfo ffff88044188e000, task ffff880440f982c0)
[2498228.006224] Stack:
[2498228.006226]  ffff8804407fec40 ffff88044188fa78 000088044188fb18 0000000000000000
[2498228.006231] <0> ffff88000184daa0 0000000000000000 0000000000000000 0000000000000008
[2498228.006238] <0> 000000000000a380 000000000000a380 ffff88000184dbb0 000000000000a380
[2498228.006245] Call Trace:
[2498228.006251]  [<ffffffff8103877d>] find_busiest_group+0x4d/0x460
[2498228.006258]  [<ffffffff814a1b53>] ? __wait_on_bit_lock+0x73/0xb0
[2498228.006262]  [<ffffffff81039294>] load_balance_newidle+0xa4/0x320
[2498228.006266]  [<ffffffff814a1623>] thread_return+0x3cc/0x429
[2498228.006272]  [<ffffffff8133b88a>] ? __up_read+0x9a/0xc0
[2498228.006277]  [<ffffffff81066607>] ? get_futex_value_locked+0x27/0x40
[2498228.006282]  [<ffffffff81066d8d>] futex_wait_queue_me+0xcd/0x110
[2498228.006286]  [<ffffffff81067878>] futex_wait+0x128/0x290
[2498228.006291]  [<ffffffff814a399d>] ? _spin_lock+0x2d/0x60
[2498228.006295]  [<ffffffff81066ee2>] ? futex_wake+0x112/0x130
[2498228.006299]  [<ffffffff81069bb9>] do_futex+0xc9/0x1b0
[2498228.006303]  [<ffffffff81069d16>] sys_futex+0x76/0x170
[2498228.006308]  [<ffffffff810edf78>] ? sys_pread64+0x88/0x90
[2498228.006315]  [<ffffffff81009ba8>] system_call_fastpath+0x16/0x1b
[2498228.006319]  [<ffffffff81009b40>] ? system_call+0x0/0x52
[2498228.006322] Code: 06 89 85 50 ff ff ff c7 85 54 ff ff ff 01 00 00 00 e9 cf fd ff ff 90 48 8b 95 70 ff ff ff 48 8b 45 a8 8b 72 08 48 c1 e0 0a 31 d2 <48> f7 f6 48 8b 75 b0 48 89 45 a0 31 c0 48 85 f6 74 0c 48 8b 45 
[2498228.006363] RIP  [<ffffffff8102ceb4>] update_sd_lb_stats+0x3a4/0x4e0
[2498228.006368]  RSP <ffff88044188f9f8>
[2498228.006372] ---[ end trace 18faee40e07dc443 ]---