[erlang-bugs] Strange application shutdown deadlock

Siri Hansen <>
Wed Jun 19 11:47:48 CEST 2013


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)
> >>> -------------------------
> >>>
> >>
> >>
> >>
> >>> _______________________________________________
> >>> erlang-bugs mailing list
> >>> 
> >>> http://erlang.org/mailman/listinfo/erlang-bugs
> >>
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> 
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