[erlang-bugs] Strange application shutdown deadlock

Tim Watson <>
Mon Jan 27 17:24:03 CET 2014


Hi Siri,

Did this bug make it into the latest release? I didn't see anything in the
release notes.

Cheers,
Tim



On 19 June 2013 10:47, Siri Hansen <> wrote:

> Hi Tim - I'm so sorry for the long delay here. I agree that this is a bug
> in the application master and I have written a ticket for it so it will be
> prioritized into out backlog.
> Thanks for the report!
> Regards
> /siri
>
>
> 2013/5/29 Tim Watson <>
>
>> Any word from the OTP folks on this one?
>>
>> On 24 May 2013, at 18:41, Tim Watson <> wrote:
>>
>> > Gah, sorry folks - this has nothing to do with release handling, that
>> was a red herring. Someone just pointed out that the call to get_child
>> originates in a status check in our code.
>> >
>> > This still looks like a bug to me though, since if you're going to
>> handle "other" messages in terminate_loop you ought to ensure they can't
>> deadlock the vm's shutdown sequence.
>> >
>> > Cheers,
>> > Tim
>> >
>> > On 24 May 2013, at 15:45, Fred Hebert <> wrote:
>> >
>> >> Quick question: are you running a release?
>> >>
>> >> If so, last time I've seen deadlocks like that was solved by making
>> sure
>> >> *all* my applications did depend on stdlib and kernel in their app
>> file.
>> >> When I skipped them, sometimes I'd find that things would lock up.
>> >>
>> >> My guess was that dependencies from stdlib or kernel got unloaded
>> before
>> >> my app and broke something, but I'm not sure -- In my case, I wasn't
>> >> able to inspect the node as it appeared to be 100% blocked.
>> >>
>> >> Adding the apps ended up fixing the problem on the next shutdown. I'm
>> >> not sure if it might be a good fix for you, but it's a stab in the
>> dark,
>> >>
>> >> Regards,
>> >> Fred.
>> >>
>> >> On 05/24, Tim Watson wrote:
>> >>> We came across this at a customer's site, where one of the nodes was
>> apparently in the process of stopping and had been in that state for at
>> least 24 hours. The short version is that an application_master appears to
>> be stuck waiting for a child pid (is that the X process, or the root
>> supervisor?) which is *not* linked to it...
>> >>>
>> >>> The application controller is in the process of stopping an
>> application, during which process a `get_child' message appears to have
>> come in to that application's application_master from somewhere - we are
>> *not* running appmon, so I'm really confused how this can happen, as the
>> only other place where I see (indirect) calls are via the sasl
>> release_handler!? At the bottom of this email is a dump for the
>> application_controller and the application_master for the app it is trying
>> to shut down. I can verify that the pid which the application_master is
>> waiting on is definitely not linked to it - i.e., process_info(links,
>> AppMasterPid) doesn't contain the process <0.256.0> that the master appears
>> to be waiting on.
>> >>>
>> >>> My reading of the code is that the application_master cannot end up
>> in get_child_i unless a get_child request was made which arrives whilst it
>> is in its terminate loop. As I said, we're not using appmon, therefore I
>> assume this originated in the sasl application's release_handler_1, though
>> I'm not sure quite which route would take us there. The relevant bit of
>> code in application_master appears to be:
>> >>>
>> >>> get_child_i(Child) ->
>> >>>   Child ! {self(), get_child},
>> >>>   receive
>> >>>   {Child, GrandChild, Mod} -> {GrandChild, Mod}
>> >>>   end.
>> >>>
>> >>> This in turn originates, I'd guess, in the third receive clause of
>> terminate_loop/2. Anyway, should that code not be dealing with a
>> potentially dead pid for Child, either by handling links effectively -
>> perhaps there is an EXIT signal in the mailbox already which is being
>> ignored here in get_child_i/1 - or by some other means?
>> >>>
>> >>> What follows below is the trace/dump output. Feel free to poke me for
>> more info as needed.
>> >>>
>> >>> Cheers,
>> >>> Tim
>> >>>
>> >>> [TRACE/DUMP]
>> >>>
>> >>> pid: <6676.7.0>
>> >>> registered name: application_controller
>> >>> stacktrace: [{application_master,call,2,
>> >>>
>>  [{file,"application_master.erl"},{line,75}]},
>> >>>            {application_controller,stop_appl,3,
>> >>>
>>  [{file,"application_controller.erl"},
>> >>>                                     {line,1393}]},
>> >>>            {application_controller,handle_call,3,
>> >>>
>>  [{file,"application_controller.erl"},
>> >>>                                     {line,810}]},
>> >>>
>>  {gen_server,handle_msg,5,[{file,"gen_server.erl"},{line,588}]}]
>> >>> -------------------------
>> >>> Program counter: 0x00007f9bf9a53720 (application_master:call/2 + 288)
>> >>> CP: 0x0000000000000000 (invalid)
>> >>> arity = 0
>> >>>
>> >>> 0x00007f9bd7948360 Return addr 0x00007f9bfb97de40
>> (application_controller:stop_appl/3 + 176)
>> >>> y(0)     #Ref<0.0.20562.258360>
>> >>> y(1)     #Ref<0.0.20562.258361>
>> >>> y(2)     []
>> >>>
>> >>> 0x00007f9bd7948380 Return addr 0x00007f9bfb973c68
>> (application_controller:handle_call/3 + 1392)
>> >>> y(0)     temporary
>> >>> y(1)     rabbitmq_web_dispatch
>> >>>
>> >>> 0x00007f9bd7948398 Return addr 0x00007f9bf9a600c8
>> (gen_server:handle_msg/5 + 272)
>> >>> y(0)
>> {state,[],[],[],[{ssl,<0.507.0>},{public_key,undefined},{crypto,<0.501.0>},{rabbitmq_web_dispatch,<0.255.0>},{webmachine,<0.250.0>},{mochiweb,undefined},{xmerl,undefined},{inets,<0.237.0>},{amqp_client,<0.233.0>},{mnesia,<0.60.0>},{sasl,<0.34.0>},{stdlib,undefined},{kernel,<0.9.0>}],[],[{ssl,temporary},{public_key,temporary},{crypto,temporary},{rabbitmq_web_dispatch,temporary},{webmachine,temporary},{mochiweb,temporary},{xmerl,temporary},{inets,temporary},{amqp_client,temporary},{mnesia,temporary},{sasl,permanent},{stdlib,permanent},{kernel,permanent}],[],[{rabbit,[{ssl_listeners,[5671]},{ssl_options,[{cacertfile,"/etc/rabbitmq/server.cacrt"},{certfile,"/etc/rabbitmq/server.crt"},{keyfile,"/etc/rabbitmq/server.key"},{verify,verify_none},{fail_if_no_peer_cert,false}]},{default_user,<<2
>> bytes>>},{default_pass,<<8
>> bytes>>},{vm_memory_high_watermark,5.000000e-01}]},{rabbitmq_management,[{listener,[{port,15672},{ssl,true}]}]}]}
>> >>> y(1)     rabbitmq_web_dispatch
>> >>> y(2)
>> [{ssl,temporary},{public_key,temporary},{crypto,temporary},{rabbitmq_web_dispatch,temporary},{webmachine,temporary},{mochiweb,temporary},{xmerl,temporary},{inets,temporary},{amqp_client,temporary},{mnesia,temporary},{sasl,permanent},{stdlib,permanent},{kernel,permanent}]
>> >>> y(3)
>> [{ssl,<0.507.0>},{public_key,undefined},{crypto,<0.501.0>},{rabbitmq_web_dispatch,<0.255.0>},{webmachine,<0.250.0>},{mochiweb,undefined},{xmerl,undefined},{inets,<0.237.0>},{amqp_client,<0.233.0>},{mnesia,<0.60.0>},{sasl,<0.34.0>},{stdlib,undefined},{kernel,<0.9.0>}]
>> >>>
>> >>> 0x00007f9bd79483c0 Return addr 0x00000000008827d8 (<terminate process
>> normally>)
>> >>> y(0)     application_controller
>> >>> y(1)
>> {state,[],[],[],[{ssl,<0.507.0>},{public_key,undefined},{crypto,<0.501.0>},{rabbitmq_web_dispatch,<0.255.0>},{webmachine,<0.250.0>},{mochiweb,undefined},{xmerl,undefined},{inets,<0.237.0>},{amqp_client,<0.233.0>},{mnesia,<0.60.0>},{sasl,<0.34.0>},{stdlib,undefined},{kernel,<0.9.0>}],[],[{ssl,temporary},{public_key,temporary},{crypto,temporary},{rabbitmq_web_dispatch,temporary},{webmachine,temporary},{mochiweb,temporary},{xmerl,temporary},{inets,temporary},{amqp_client,temporary},{mnesia,temporary},{sasl,permanent},{stdlib,permanent},{kernel,permanent}],[],[{rabbit,[{ssl_listeners,[5671]},{ssl_options,[{cacertfile,"/etc/rabbitmq/server.cacrt"},{certfile,"/etc/rabbitmq/server.crt"},{keyfile,"/etc/rabbitmq/server.key"},{verify,verify_none},{fail_if_no_peer_cert,false}]},{default_user,<<2
>> bytes>>},{default_pass,<<8
>> bytes>>},{vm_memory_high_watermark,5.000000e-01}]},{rabbitmq_management,[{listener,[{port,15672},{ssl,true}]}]}]}
>> >>> y(2)     application_controller
>> >>> y(3)     <0.2.0>
>> >>> y(4)     {stop_application,rabbitmq_web_dispatch}
>> >>> y(5)     {<0.5864.275>,#Ref<0.0.20562.258345>}
>> >>> y(6)     Catch 0x00007f9bf9a600c8 (gen_server:handle_msg/5 + 272)
>> >>> -------------------------
>> >>>
>> >>> pid: <6676.255.0>
>> >>> registered name: none
>> >>> stacktrace: [{application_master,get_child_i,1,
>> >>>
>>  [{file,"application_master.erl"},{line,392}]},
>> >>>            {application_master,handle_msg,2,
>> >>>
>>  [{file,"application_master.erl"},{line,216}]},
>> >>>            {application_master,terminate_loop,2,
>> >>>
>>  [{file,"application_master.erl"},{line,206}]},
>> >>>            {application_master,terminate,2,
>> >>>
>>  [{file,"application_master.erl"},{line,227}]},
>> >>>            {application_master,handle_msg,2,
>> >>>
>>  [{file,"application_master.erl"},{line,219}]},
>> >>>            {application_master,main_loop,2,
>> >>>
>>  [{file,"application_master.erl"},{line,194}]},
>> >>>
>>  {proc_lib,init_p_do_apply,3,[{file,"proc_lib.erl"},{line,227}]}]
>> >>> -------------------------
>> >>> Program counter: 0x00007f9bf9a570e0 (application_master:get_child_i/1
>> + 120)
>> >>> CP: 0x0000000000000000 (invalid)
>> >>> arity = 0
>> >>>
>> >>> 0x00007f9c1adc3dc8 Return addr 0x00007f9bf9a54eb0
>> (application_master:handle_msg/2 + 280)
>> >>> y(0)     <0.256.0>
>> >>>
>> >>> 0x00007f9c1adc3dd8 Return addr 0x00007f9bf9a54d20
>> (application_master:terminate_loop/2 + 520)
>> >>> y(0)     #Ref<0.0.20562.258362>
>> >>> y(1)     <0.9596.275>
>> >>> y(2)
>> {state,<0.256.0>,{appl_data,rabbitmq_web_dispatch,[],undefined,{rabbit_web_dispatch_app,[]},[rabbit_web_dispatch,rabbit_web_dispatch_app,rabbit_web_dispatch_registry,rabbit_web_dispatch_sup,rabbit_web_dispatch_util,rabbit_webmachine],[],infinity,infinity},[],0,<0.29.0>}
>> >>>
>> >>> 0x00007f9c1adc3df8 Return addr 0x00007f9bf9a55108
>> (application_master:terminate/2 + 192)
>> >>> y(0)     <0.256.0>
>> >>>
>> >>> 0x00007f9c1adc3e08 Return addr 0x00007f9bf9a54f70
>> (application_master:handle_msg/2 + 472)
>> >>> y(0)     []
>> >>> y(1)     normal
>> >>>
>> >>> 0x00007f9c1adc3e20 Return addr 0x00007f9bf9a54a60
>> (application_master:main_loop/2 + 1600)
>> >>> y(0)     <0.7.0>
>> >>> y(1)     #Ref<0.0.20562.258360>
>> >>> y(2)     Catch 0x00007f9bf9a54f70 (application_master:handle_msg/2 +
>> 472)
>> >>>
>> >>> 0x00007f9c1adc3e40 Return addr 0x00007f9bfb969420
>> (proc_lib:init_p_do_apply/3 + 56)
>> >>> y(0)     <0.7.0>
>> >>>
>> >>> 0x00007f9c1adc3e50 Return addr 0x00000000008827d8 (<terminate process
>> normally>)
>> >>> y(0)     Catch 0x00007f9bfb969440 (proc_lib:init_p_do_apply/3 + 88)
>> >>> -------------------------
>> >>>
>> >>
>> >>
>> >>
>> >>> _______________________________________________
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>> >>> 
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>> >>
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