[erlang-questions] [erlang-bugs] beam core file R17

[Mikael Pettersson]

Matthew Evans writes:
 > Hi,
 > This core was found on a live system (R17):
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 > 10:16:38:# erl
 > Erlang/OTP 17 [erts-6.2] [source] [64-bit] [smp:8:8] [async-threads:10] [hipe] [kernel-poll:false]
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 > Eshell V6.2  (abort with ^G)
 > 1> 
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 > ........
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 > May 28 22:18:56 [info   ] plexxi kernel: [1235119.885465] beam.smp[2267] general protection ip:4b698a sp:7faeb6a7d650 error:0 in beam.smp[400000+1ac000]
 > warning: Can't read pathname for load map: Input/output error.[Thread debugging using libthread_db enabled]Using host libthread_db library "/lib/libthread_db.so.1".Core was generated by `/usr/lib/erlang/erts-6.2/bin/beam.smp -K true -A 24 -P 350000 -- -root /usr/lib'.Program terminated with signal 11, Segmentation fault.#0  0x00000000004b698a in sweep_off_heap ()(gdb) bt#0  0x00000000004b698a in sweep_off_heap ()#1  0x00000000004b77d1 in do_minor ()#2  0x00000000004b8479 in erts_garbage_collect ()#3  0x00000000004e1374 in process_main ()#4  0x000000000048071d in sched_thread_func ()#5  0x0000000000549f89 in thr_wrapper ()#6  0x00007faeba32ba30 in start_thread () from /lib/libpthread.so.0#7  0x00007faeb9e8a53d in clone () from /lib/libc.so.6

It looks like your beam.smp binary lacks debugging information, so we only know the general
area where it crashed (sweep_off_heap() as called from do_minor()).  Crashes here would usually
be due to memory corruption, which could be caused by:
- a bug in the VM
- a bug in a NIF
- a bug in HiPE
- a bug in the C compiler used to compile the VM (I've seen that happen at least 3 times)
- a HW error (though you'd then also find e.g. machine check events logged)

If you want to debug this, you should first ensure that your beam.smp gets built and installed
with full debugging information (just attach gdb, bt, and list to verify).  You should also try
without NIFs or native code, if those are used and you can configure them not to be.