[erlang-questions] OTP 20.0.2 segfault at 5c ip in beam.smp

[Sverker Eriksson]

You can provoke a VM "crash" with erlang:halt(abort) to test if the OS 
creates a core dump file.


/Sverker


On 08/16/2017 05:10 PM, Lukas Larsson wrote:
> You need to instruct the operating system to save a core dump,
> http://man7.org/linux/man-pages/man5/core.5.html.
>
> Some operating systems can be configured to dump parts of the core dump to
> the syslog when a segfault happens, which can be useful but a full core
> dump contains much more information so is a lot more useful.
>
> Lukas
>
> On Wed, Aug 16, 2017 at 5:00 PM, Gerhard Lazu <gerhard@REDACTED> wrote:
>
>> The crash dump was never generated because the Erlang VM segfaulted.
>>
>> Is there a way to force extra debugging output in segfault scenarios?
>>
>> On Wed, Aug 16, 2017 at 1:42 PM, Lukas Larsson <lukas@REDACTED> wrote:
>>
>>> Hello,
>>>
>>> In order to debug this we need access to a core file generated from the
>>> crash and also the beam.smp binary that was used to run it.
>>>
>>> Lukas
>>>
>>> On Wed, Aug 16, 2017 at 1:20 PM, Gerhard Lazu <gerhard@REDACTED> wrote:
>>>
>>>> Hi,
>>>>
>>>> A RabbitMQ 3.6.11-rc.3 node crashed when OTP 20.0.2 segfaulted. This is
>>>> the only information that we have about the Erlang VM itself:
>>>>
>>>>      Aug 16 04:08:59 localhost kernel: [61139.180699] 2_scheduler[15162]:
>>>> segfault at 5c ip 00000000005ba760 sp 00007f8fea1ffc40 err
>>>> or 4 in beam.smp[400000+333000]
>>>>
>>>> This is the last line logged by RMQ, 2 seconds before the Erlang VM
>>>> segfault:
>>>>
>>>>      =INFO REPORT==== 16-Aug-2017::04:08:57 === closing AMQP connection
>>>> <0.24230.9> (10.0.16.35:42562 -> 10.0.16.23:5672, vhost: '/', user:
>>>> 'admin')
>>>>
>>>> beam.smp runs with the following flags:
>>>>
>>>>      /var/vcap/packages/erlang-20.0.2/lib/erlang/erts-9.0.2/bin/beam.smp
>>>> -W w -A 64 -P 1048576 -t 5000000 -stbt db -zdbbl 128000 -K true -- -root
>>>> /var/vcap/packages/erlang-20.0.2/lib/erlang -progname erl -- -home
>>>> /home/vcap -- -pa /var/vcap/jobs/rabbitmq-server/packages/rabbitmq-server/ebin
>>>> -noshell -noinput -s rabbit boot -sname rabbit@REDACTED -boot
>>>> start_sasl -config /var/vcap/jobs/rabbitmq-server/rabbitmq -kernel
>>>> inet_default_connect_options [{nodelay,true}] -sasl errlog_type error -sasl
>>>> sasl_error_logger false -rabbit error_logger {file,"/var/vcap/sys/log/rabbi
>>>> tmq-server/rabbit@REDACTED"} -rabbit sasl_error_logger
>>>> {file,"/var/vcap/sys/log/rabbitmq-server/rabbit@REDACTED"}
>>>> -rabbit enabled_plugins_file "/var/vcap/jobs/rabbitmq-serve
>>>> r/packages/rabbitmq-server/etc/rabbitmq/enabled_plugins" -rabbit
>>>> plugins_dir "/var/vcap/jobs/rabbitmq-server/packages/rabbitmq-server/plugins"
>>>> -rabbit plugins_expand_dir "/var/vcap/store/rabbitmq-serv
>>>> er/mnesia/rabbit@REDACTED" -os_mon start_cpu_sup
>>>> false -os_mon start_disksup false -os_mon start_memsup false -mnesia dir
>>>> "/var/vcap/store/rabbitmq-server/mnesia/rabbit@REDACTED" -kernel
>>>> inet_dist_listen_min 25672 -kernel inet_dist_listen_max 25672
>>>>
>>>> We are running on:
>>>>
>>>>      4.4.0-83-generic #106~14.04.1-Ubuntu SMP Mon Jun 26 18:10:19 UTC
>>>> 2017 x86_64 GNU/Linux
>>>>
>>>> When this happens again, how do I capture more debugging information? I
>>>> would like to file an OTP bug report, but I'm not sure that we have enough
>>>> information.
>>>>
>>>> Apparently, this was reported at least once before, against OTP 18.1:
>>>> https://github.com/rabbitmq/rabbitmq-server/issues/459
>>>>
>>>> Thank you, Gerhard.
>>>>
>>>> _______________________________________________
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>>>>
>>>>
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