[erlang-bugs] beam core'ing

Patrik Nyblom <>
Mon Nov 19 14:54:31 CET 2012

On 11/19/2012 02:01 PM, Musumeci, Antonio S wrote:
> I'm just starting to debug this but figured I'd send it along in case 
> anyone has seen this before.
> 64bit RHEL 5.0.1
> built from source beam.smp R15B02
> Happens consistently when trying to start our app and then just stops 
> after a time. Across a few boxes. Oddly we have an identical cluster 
> (hw and sw) and it never happens.
Yes! I've seen it before and have tried for several months to get 
areproducable example and acore i can analyze here. I've had one core 
that wassomewhat readable but had no luck in locating the beam code that 
triggered this. If you could try narrowing it down, I would be really 

Please email me any findings, theories, cores dumps- anything! I really 
want to find this! The most interesting would be to find the snippet of 
erlang code that makes this happen (intermittently probably).

The problem is that when the allocators crash, the error is usually 
somewhere else. Access of freed memory, double free or something else 
doing horrid things to memory. Obviously none of our testsuites exercise 
this bug as neither our debug builds, nor our valgrind runs find it. It 
happens on both SMP and non SMP and is always in the context of the 
erts_bs_append, so I'm pretty sure this has a connection to the other 
users seeing the crash in the allocators...

> #0 bf_unlink_free_block (flags=<optimized out>, block=0x6f00, 
> allctr=<optimized out>) at beam/erl_bestfit_alloc.c:789
> #1 bf_get_free_block (allctr=0x6824600, size=304, cand_blk=0x0, 
> cand_size=<optimized out>, flags=0) at beam/erl_bestfit_alloc.c:869
> #2 0x000000000045343c in mbc_alloc_block (alcu_flgsp=<optimized out>, 
> blk_szp=<optimized out>, size=<optimized out>, allctr=<optimized out>) 
> at beam/erl_alloc_util.c:1198
> #3 mbc_alloc (allctr=0x6824600, size=295) at beam/erl_alloc_util.c:1345
> #4 0x000000000045398d in do_erts_alcu_alloc (type=164, 
> extra=0x6824600, size=295) at beam/erl_alloc_util.c:3442
> #5 0x0000000000453a0f in erts_alcu_alloc_thr_pref (type=164, 
> extra=<optimized out>, size=287) at beam/erl_alloc_util.c:3520
> #6 0x0000000000511463 in erts_alloc (size=287, type=<optimized out>) 
> at beam/erl_alloc.h:208
> #7 erts_bin_nrml_alloc (size=<optimized out>) at beam/erl_binary.h:260
> #8 erts_bs_append (c_p=0x69fba60, reg=<optimized out>, live=<optimized 
> out>, build_size_term=<optimized out>, extra_words=0, unit=8)at 
> beam/erl_bits.c:1327
> #9 0x000000000053ffd8 in process_main () at beam/beam_emu.c:3858
> #10 0x00000000004ae853 in sched_thread_func (vesdp=<optimized out>) at 
> beam/erl_process.c:5184
> #11 0x00000000005c17e9 in thr_wrapper (vtwd=<optimized out>) at 
> pthread/ethread.c:106
> #12 0x00002b430f39e73d in start_thread () from /lib64/libpthread.so.0
> #13 0x00002b430f890f6d in clone () from /lib64/libc.so.6
> #14 0x0000000000000000 in ?? ()
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