[erlang-bugs] VM locks up on write to socket (and now it seems to file too)

[Patrik Nyblom]

Hi again!

No problem reproducing when I've got CentOS 6.3... The following 
commands in the Erlang shell:
{ok,L} = gen_tcp:listen(4747,[{active,false}]).
{ok,S} = gen_tcp:connect("localhost",4747,[{active,false}]).
{ok,A} = gen_tcp:accept(L).
gen_tcp:send(A,binary:copy(<<$a:8>>,2158022464)).

gives the following strace:
[pid 15859] writev(10, [{"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"..., 
2158022464}], 1) = 0
[pid 15859] writev(10, [{"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"..., 
2158022464}], 1) = 0
[pid 15859] writev(10, [{"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"..., 
2158022464}], 1) = 0
[pid 15859] writev(10, [{"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"..., 
2158022464}], 1) = 0
[pid 15859] writev(10, [{"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"..., 
2158022464}], 1) = 0
[pid 15859] writev(10, [{"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"..., 
2158022464}], 1) = 0
[pid 15859] writev(10, [{"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"..., 
2158022464}], 1) = 0
[pid 15859] writev(10, [{"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"..., 
2158022464}], 1) = 0
[pid 15859] writev(10, [{"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"..., 
2158022464}], 1) = 0
[pid 15859] writev(10, [{"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"..., 
2158022464}], 1) = 0
[pid 15859] writev(10, [{"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"..., 
2158022464}], 1) = 0
[.....]

While on ubuntu for example it works like it should...Looks like a 
kernel bug to me... I wonder if this should be worked around or just 
reported... I suppose both... Sigh...

/Patrik

On 11/28/2012 05:23 PM, Peter Membrey wrote:
> Hi,
>
> No problem, I'll do what I can to help - thanks for looking into this
> so quickly!
>
> Any idea what might be causing it?
>
> Cheers,
>
> Pete
>
> On 28 November 2012 23:54, Patrik Nyblom <pan@REDACTED> wrote:
>> Hi!
>>
>> I'll upgrade the CentOS VM I have to 6.3 (only had 6.1 :() and see if I can
>> reproduce. If that fails, could you run a VM with a patch to try to handle
>> the unexpected case and see if that fixes it?
>>
>> Cheers,
>> /Patrik
>>
>> On 11/24/2012 02:57 PM, Peter Membrey wrote:
>>> Hi guys,
>>>
>>> Thanks for getting back in touch so quickly!
>>>
>>> I did do an lsof on the process and I can confirm that it was
>>> definitely a socket. However by that time the application it had been
>>> trying to send to had been killed. When I checked the sockets were
>>> showing as waiting to close. Unfortunately I didn't think to do an
>>> lsof until after the apps had been shut down. I was hoping the VM
>>> would recover if I killed the app that had upset it. However even
>>> after all the apps connected had been shut down, the issue didn't
>>> resolve.
>>>
>>> The application receives requests from a client, which contains two
>>> data items. The stream ID and a timestamp. Both are encoded as big
>>> integer unsigned numbers. The server then looks through the file
>>> referenced by the stream ID and uses the timestamp as an index. The
>>> file format is currently really simple, in the form of:
>>>
>>> <Timestamp:64/native-integer,Length:32/native-integer,Data:Length/binary>>
>>>
>>> There is an index file that provides an offset into the file based on
>>> time stamp, but basically it opens the file, and reads sequentially
>>> through it until it finds the timestamps that it cares about. In this
>>> case it reads all data with a greater timestamp until the end of the
>>> file is reached. It's possible the client is sending an incorrect
>>> timestamp, and maybe too much data is being read. However the loop is
>>> very primitive - it reads all the data in one go before passing it
>>> back to the protocol handler to send down the socket; so by that time
>>> even though the response is technically incorrect and the app has
>>> failed, it should still not cause the VM any issues.
>>>
>>> The data is polled every 10 seconds by the client app so I would not
>>> expect there to be 2GB of new data to send. I'm afraid my C skills are
>>> somewhat limited, so I'm not sure how to put together a sample app to
>>> try out writev. The platform is 64bit CentOS 6.3 (equivalent to RHEL
>>> 6.3) so I'm not expecting any strange or weird behaviour from the OS
>>> level but of course I could be completely wrong there. The OS is
>>> running directly on hardware, so there's no VM layer to worry about.
>>>
>>> Hope this might offer some additional clues…
>>>
>>> Thanks again!
>>>
>>> Kind Regards,
>>>
>>> Peter Membrey
>>>
>>>
>>>
>>> On 24 November 2012 00:13, Patrik Nyblom <pan@REDACTED> wrote:
>>>> Hi again!
>>>>
>>>> Could you go back to the version without the printouts and get back to
>>>> the
>>>> situation where writev loops returning 0 (as in the strace)? If so, it
>>>> would
>>>> be really interesting to see an 'lsof' of the beam process, to see if
>>>> this
>>>> file descriptor really is open and is a socket...
>>>>
>>>> The thing is that writev with a vector that is not empty, would never
>>>> return
>>>> 0 for a non blocking socket. Not on any modern (i.e. not ancient) POSIX
>>>> compliant system anyway. Of course it is a *really* large item you are
>>>> trying to write there, but it should be no problem for a 64bit linux.
>>>>
>>>> Also I think there is no use finding the Erlang code, I'll take that
>>>> back,
>>>> It would be more interesting to see what really happens at the OS/VM
>>>> level
>>>> in this case.
>>>>
>>>> Cheers,
>>>> Patrik
>>>>
>>>>
>>>> On 11/23/2012 01:49 AM, Loïc Hoguin wrote:
>>>>> Sending this on behalf of someone who didn't manage to get the email
>>>>> sent
>>>>> to this list after 2 attempts. If someone can check if he's hold up or
>>>>> something that'd be great.
>>>>>
>>>>> Anyway he has a big issue so I hope I can relay the conversation
>>>>> reliably.
>>>>>
>>>>> Thanks!
>>>>>
>>>>> On 11/23/2012 01:45 AM, Peter Membrey wrote:
>>>>>> From: Peter Membrey <peter@REDACTED>
>>>>>> Date: 22 November 2012 19:02
>>>>>> Subject: VM locks up on write to socket (and now it seems to file too)
>>>>>> To: erlang-bugs@REDACTED
>>>>>>
>>>>>>
>>>>>> Hi guys,
>>>>>>
>>>>>> I wrote a simple database application called CakeDB
>>>>>> (https://github.com/pmembrey/cakedb) that basically spends its time
>>>>>> reading and writing files and sockets. There's very little in the way
>>>>>> of complex logic. It is running on CentOS 6.3 with all the updates
>>>>>> applied. I hit this problem on R15B02 so I rolled back to R15B01 but
>>>>>> the issue remained. Erlang was built from source.
>>>>>>
>>>>>> The machine has two Intel X5690 CPUs giving 12 cores plus HT. I've
>>>>>> tried various arguments for the VM but so far nothing has prevented
>>>>>> the problem. At the moment I'm using:
>>>>>>
>>>>>> +K
>>>>>> +A 6
>>>>>> +sbt tnnps
>>>>>>
>>>>>> The issue I'm seeing is that one of the scheduler threads will hit
>>>>>> 100% cpu usage and the entire VM will become unresponsive. When this
>>>>>> happens, I am not able to connect via the console with attach and
>>>>>> entop is also unable to connect. I can still establish TCP connections
>>>>>> to the application, but I never receive a response. A standard kill
>>>>>> signal will cause the VM to shut down (it doesn't need -9).
>>>>>>
>>>>>> Due to the pedigree of the VM I am quite willing to accept that I've
>>>>>> made a fundamental mistake in my code. I am pretty sure that the way I
>>>>>> am doing the file IO could result in some race conditions. However, my
>>>>>> poor code aside, from what I understand, I still shouldn't be able to
>>>>>> crash / deadlock the VM like this.
>>>>>>
>>>>>> The issue doesn't seem to be caused by load. The app can fail when
>>>>>> it's very busy, but also when it is practically idle. I haven't been
>>>>>> able to find a trigger or any other explanation for the failure.
>>>>>>
>>>>>> The thread maxing out the CPU is attempting to write data to the
>>>>>> socket:
>>>>>>
>>>>>> (gdb) bt
>>>>>> #0  0x00007f9882ab6377 in writev () from /lib64/libc.so.6
>>>>>> #1  0x000000000058a81f in tcp_inet_output (data=0x2407570,
>>>>>> event=<value optimized out>) at drivers/common/inet_drv.c:9681
>>>>>> #2  tcp_inet_drv_output (data=0x2407570, event=<value optimized out>)
>>>>>> at drivers/common/inet_drv.c:9601
>>>>>> #3  0x00000000004b773f in erts_port_task_execute (runq=0x7f98826019c0,
>>>>>> curr_port_pp=0x7f9881639338)  at beam/erl_port_task.c:858
>>>>>> #4  0x00000000004afd83 in schedule (p=<value optimized out>,
>>>>>> calls=<value optimized out>) at beam/erl_process.c:6533
>>>>>> #5  0x0000000000539ca2 in process_main () at beam/beam_emu.c:1268
>>>>>> #6  0x00000000004b1279 in sched_thread_func (vesdp=0x7f9881639280) at
>>>>>> beam/erl_process.c:4834
>>>>>> #7  0x00000000005ba726 in thr_wrapper (vtwd=0x7fff6cfe2300) at
>>>>>> pthread/ethread.c:106
>>>>>> #8  0x00007f9882f78851 in start_thread () from /lib64/libpthread.so.0
>>>>>> #9  0x00007f9882abe11d in clone () from /lib64/libc.so.6
>>>>>> (gdb)
>>>>>>
>>>>>> I then tried running strace on that thread and got (indefinitely):
>>>>>>
>>>>>> writev(15, [{"", 2158022464}], 1)       = 0
>>>>>> writev(15, [{"", 2158022464}], 1)       = 0
>>>>>> writev(15, [{"", 2158022464}], 1)       = 0
>>>>>> writev(15, [{"", 2158022464}], 1)       = 0
>>>>>> writev(15, [{"", 2158022464}], 1)       = 0
>>>>>> writev(15, [{"", 2158022464}], 1)       = 0
>>>>>> writev(15, [{"", 2158022464}], 1)       = 0
>>>>>> writev(15, [{"", 2158022464}], 1)       = 0
>>>>>> writev(15, [{"", 2158022464}], 1)       = 0
>>>>>> writev(15, [{"", 2158022464}], 1)       = 0
>>>>>> ...
>>>>>>
>>>>>>    From what I can tell, it's trying to write data to a socket, which is
>>>>>> succeeding, but writing 0 bytes. From the earlier definitions in the
>>>>>> source file, an error condition would be signified by a negative
>>>>>> number. Any other result is the number of bytes written, in this case
>>>>>> 0. I'm not sure if this is desired behaviour or not. I've tried
>>>>>> killing the application on the other end of the socket, but it has no
>>>>>> effect on the VM.
>>>>>>
>>>>>> I have enabled debugging for the inet code, so hopefully this will
>>>>>> give a little more insight. I am currently trying to reproduce the
>>>>>> condition, but as I really have no idea what causes it, it's pretty
>>>>>> much a case of wait and see.
>>>>>>
>>>>>>
>>>>>> **** UPDATE ****
>>>>>>
>>>>>> I managed to lock up the VM again, but this time it was caused by file
>>>>>> IO,
>>>>>> probably from the debugging statements. Although it worked fine for
>>>>>> some
>>>>>> time
>>>>>> the last entry in the file was cut off.
>>>>>>
>>>>>>    From GDB:
>>>>>>
>>>>>> (gdb) info threads
>>>>>>      53 Thread 0x7f83e988b700 (LWP 8621)  0x00007f83ea6da54d in read ()
>>>>>> from /lib64/libpthread.so.0
>>>>>>      52 Thread 0x7f83e8c8f700 (LWP 8622)  0x00007f83ea6d743c in
>>>>>> pthread_cond_wait@@GLIBC_2.3.2 () from /lib64/libpthread.so.0
>>>>>>      51 Thread 0x7f83e818d700 (LWP 8623)  0x00007f83ea215ae9 in syscall
>>>>>> () from /lib64/libc.so.6
>>>>>>      50 Thread 0x7f83e816b700 (LWP 8624)  0x00007f83ea215ae9 in syscall
>>>>>> () from /lib64/libc.so.6
>>>>>>      49 Thread 0x7f83e8149700 (LWP 8625)  0x00007f83ea215ae9 in syscall
>>>>>> () from /lib64/libc.so.6
>>>>>>      48 Thread 0x7f83e8127700 (LWP 8626)  0x00007f83ea215ae9 in syscall
>>>>>> () from /lib64/libc.so.6
>>>>>>      47 Thread 0x7f83e8105700 (LWP 8627)  0x00007f83ea215ae9 in syscall
>>>>>> () from /lib64/libc.so.6
>>>>>>      46 Thread 0x7f83e80e3700 (LWP 8628)  0x00007f83ea215ae9 in syscall
>>>>>> () from /lib64/libc.so.6
>>>>>>      45 Thread 0x7f83e80c1700 (LWP 8629)  0x00007f83ea215ae9 in syscall
>>>>>> () from /lib64/libc.so.6
>>>>>>      44 Thread 0x7f83e809f700 (LWP 8630)  0x00007f83ea215ae9 in syscall
>>>>>> () from /lib64/libc.so.6
>>>>>>      43 Thread 0x7f83e807d700 (LWP 8631)  0x00007f83ea215ae9 in syscall
>>>>>> () from /lib64/libc.so.6
>>>>>>      42 Thread 0x7f83e805b700 (LWP 8632)  0x00007f83ea215ae9 in syscall
>>>>>> () from /lib64/libc.so.6
>>>>>>      41 Thread 0x7f83e8039700 (LWP 8633)  0x00007f83ea215ae9 in syscall
>>>>>> () from /lib64/libc.so.6
>>>>>>      40 Thread 0x7f83e8017700 (LWP 8634)  0x00007f83ea215ae9 in syscall
>>>>>> () from /lib64/libc.so.6
>>>>>>      39 Thread 0x7f83e7ff5700 (LWP 8635)  0x00007f83ea215ae9 in syscall
>>>>>> () from /lib64/libc.so.6
>>>>>>      38 Thread 0x7f83e7fd3700 (LWP 8636)  0x00007f83ea215ae9 in syscall
>>>>>> () from /lib64/libc.so.6
>>>>>>      37 Thread 0x7f83e7fb1700 (LWP 8637)  0x00007f83ea215ae9 in syscall
>>>>>> () from /lib64/libc.so.6
>>>>>>      36 Thread 0x7f83e7f8f700 (LWP 8638)  0x00007f83ea215ae9 in syscall
>>>>>> () from /lib64/libc.so.6
>>>>>>      35 Thread 0x7f83e7f6d700 (LWP 8639)  0x00007f83ea215ae9 in syscall
>>>>>> () from /lib64/libc.so.6
>>>>>>      34 Thread 0x7f83e7f4b700 (LWP 8640)  0x00007f83ea215ae9 in syscall
>>>>>> () from /lib64/libc.so.6
>>>>>>      33 Thread 0x7f83e7f29700 (LWP 8641)  0x00007f83ea215ae9 in syscall
>>>>>> () from /lib64/libc.so.6
>>>>>>      32 Thread 0x7f83e7f07700 (LWP 8642)  0x00007f83ea215ae9 in syscall
>>>>>> () from /lib64/libc.so.6
>>>>>>      31 Thread 0x7f83e7ee5700 (LWP 8643)  0x00007f83ea215ae9 in syscall
>>>>>> () from /lib64/libc.so.6
>>>>>>      30 Thread 0x7f83e7ec3700 (LWP 8644)  0x00007f83ea215ae9 in syscall
>>>>>> () from /lib64/libc.so.6
>>>>>>      29 Thread 0x7f83e7ea1700 (LWP 8645)  0x00007f83ea215ae9 in syscall
>>>>>> () from /lib64/libc.so.6
>>>>>>      28 Thread 0x7f83e7e7f700 (LWP 8646)  0x00007f83ea215ae9 in syscall
>>>>>> () from /lib64/libc.so.6
>>>>>>      27 Thread 0x7f83d7c5a700 (LWP 8647)  0x00007f83ea6db09d in waitpid
>>>>>> () from /lib64/libpthread.so.0
>>>>>>      26 Thread 0x7f83d7c53700 (LWP 8648)  0x00007f83ea215ae9 in syscall
>>>>>> () from /lib64/libc.so.6
>>>>>>      25 Thread 0x7f83d7252700 (LWP 8649)  0x00007f83ea215ae9 in syscall
>>>>>> () from /lib64/libc.so.6
>>>>>>      24 Thread 0x7f83d6851700 (LWP 8650)  0x00007f83ea215ae9 in syscall
>>>>>> () from /lib64/libc.so.6
>>>>>>      23 Thread 0x7f83d5e50700 (LWP 8651)  0x00007f83ea215ae9 in syscall
>>>>>> () from /lib64/libc.so.6
>>>>>>      22 Thread 0x7f83d544f700 (LWP 8652)  0x00007f83ea215ae9 in syscall
>>>>>> () from /lib64/libc.so.6
>>>>>>      21 Thread 0x7f83d4a4e700 (LWP 8653)  0x00007f83ea215ae9 in syscall
>>>>>> () from /lib64/libc.so.6
>>>>>>      20 Thread 0x7f83d404d700 (LWP 8654)  0x00007f83ea20be7d in write ()
>>>>>> from /lib64/libc.so.6
>>>>>>      19 Thread 0x7f83d364c700 (LWP 8655)  0x00007f83ea215ae9 in syscall
>>>>>> () from /lib64/libc.so.6
>>>>>>      18 Thread 0x7f83d2c4b700 (LWP 8656)  0x00007f83ea215ae9 in syscall
>>>>>> () from /lib64/libc.so.6
>>>>>>      17 Thread 0x7f83d224a700 (LWP 8657)  0x00007f83ea215ae9 in syscall
>>>>>> () from /lib64/libc.so.6
>>>>>>      16 Thread 0x7f83d1849700 (LWP 8658)  0x00007f83ea215ae9 in syscall
>>>>>> () from /lib64/libc.so.6
>>>>>>      15 Thread 0x7f83d0e48700 (LWP 8659)  0x00007f83ea215ae9 in syscall
>>>>>> () from /lib64/libc.so.6
>>>>>>      14 Thread 0x7f83d0447700 (LWP 8660)  0x00007f83ea215ae9 in syscall
>>>>>> () from /lib64/libc.so.6
>>>>>>      13 Thread 0x7f83cfa46700 (LWP 8661)  0x00007f83ea215ae9 in syscall
>>>>>> () from /lib64/libc.so.6
>>>>>>      12 Thread 0x7f83cf045700 (LWP 8662)  0x00007f83ea215ae9 in syscall
>>>>>> () from /lib64/libc.so.6
>>>>>>      11 Thread 0x7f83ce644700 (LWP 8663)  0x00007f83ea215ae9 in syscall
>>>>>> () from /lib64/libc.so.6
>>>>>>      10 Thread 0x7f83cdc43700 (LWP 8664)  0x00007f83ea215ae9 in syscall
>>>>>> () from /lib64/libc.so.6
>>>>>>      9 Thread 0x7f83cd242700 (LWP 8665)  0x00007f83ea215ae9 in syscall
>>>>>> ()
>>>>>> from /lib64/libc.so.6
>>>>>>      8 Thread 0x7f83cc841700 (LWP 8666)  0x00007f83ea215ae9 in syscall
>>>>>> ()
>>>>>> from /lib64/libc.so.6
>>>>>>      7 Thread 0x7f83cbe40700 (LWP 8667)  0x00007f83ea215ae9 in syscall
>>>>>> ()
>>>>>> from /lib64/libc.so.6
>>>>>>      6 Thread 0x7f83cb43f700 (LWP 8668)  0x00007f83ea215ae9 in syscall
>>>>>> ()
>>>>>> from /lib64/libc.so.6
>>>>>>      5 Thread 0x7f83caa3e700 (LWP 8669)  0x00007f83ea215ae9 in syscall
>>>>>> ()
>>>>>> from /lib64/libc.so.6
>>>>>>      4 Thread 0x7f83ca03d700 (LWP 8670)  0x00007f83ea215ae9 in syscall
>>>>>> ()
>>>>>> from /lib64/libc.so.6
>>>>>>      3 Thread 0x7f83c963c700 (LWP 8671)  0x00007f83ea215ae9 in syscall
>>>>>> ()
>>>>>> from /lib64/libc.so.6
>>>>>>      2 Thread 0x7f83c8c3b700 (LWP 8672)  0x00007f83ea215ae9 in syscall
>>>>>> ()
>>>>>> from /lib64/libc.so.6
>>>>>> * 1 Thread 0x7f83eb3a8700 (LWP 8597)  0x00007f83ea211d03 in select ()
>>>>>> from /lib64/libc.so.6
>>>>>> (gdb)
>>>>>>
>>>>>>
>>>>>> (gdb) bt
>>>>>> #0  0x00007f83ea20be7d in write () from /lib64/libc.so.6
>>>>>> #1  0x00007f83ea1a2583 in _IO_new_file_write () from /lib64/libc.so.6
>>>>>> #2  0x00007f83ea1a3b35 in _IO_new_do_write () from /lib64/libc.so.6
>>>>>> #3  0x00007f83ea1a21fd in _IO_new_file_xsputn () from /lib64/libc.so.6
>>>>>> #4  0x00007f83ea17589d in vfprintf () from /lib64/libc.so.6
>>>>>> #5  0x00007f83ea18003a in printf () from /lib64/libc.so.6
>>>>>> #6  0x000000000058f0e8 in tcp_recv (desc=0x2c3d350, request_len=0) at
>>>>>> drivers/common/inet_drv.c:8976
>>>>>> #7  0x000000000058f63a in tcp_inet_input (data=0x2c3d350, event=<value
>>>>>> optimized out>) at drivers/common/inet_drv.c:9326
>>>>>> #8  tcp_inet_drv_input (data=0x2c3d350, event=<value optimized out>)
>>>>>> at drivers/common/inet_drv.c:9604
>>>>>> #9  0x00000000004b770f in erts_port_task_execute (runq=0x7f83e9d5d3c0,
>>>>>> curr_port_pp=0x7f83e8dc6e78) at beam/erl_port_task.c:851
>>>>>> #10 0x00000000004afd83 in schedule (p=<value optimized out>,
>>>>>> calls=<value optimized out>) at beam/erl_process.c:6533
>>>>>> #11 0x0000000000539ca2 in process_main () at beam/beam_emu.c:1268
>>>>>> #12 0x00000000004b1279 in sched_thread_func (vesdp=0x7f83e8dc6dc0) at
>>>>>> beam/erl_process.c:4834
>>>>>> #13 0x00000000005bb3e6 in thr_wrapper (vtwd=0x7fffe8266da0) at
>>>>>> pthread/ethread.c:106
>>>>>> #14 0x00007f83ea6d3851 in start_thread () from /lib64/libpthread.so.0
>>>>>> #15 0x00007f83ea21911d in clone () from /lib64/libc.so.6
>>>>>> (gdb)
>>>>>>
>>>>>> (gdb) bt
>>>>>> #0  0x00007f83ea6da54d in read () from /lib64/libpthread.so.0
>>>>>> #1  0x0000000000554b6e in signal_dispatcher_thread_func (unused=<value
>>>>>> optimized out>) at sys/unix/sys.c:2776
>>>>>> #2  0x00000000005bb3e6 in thr_wrapper (vtwd=0x7fffe8266c80) at
>>>>>> pthread/ethread.c:106
>>>>>> #3  0x00007f83ea6d3851 in start_thread () from /lib64/libpthread.so.0
>>>>>> #4  0x00007f83ea21911d in clone () from /lib64/libc.so.6
>>>>>> (gdb)
>>>>>>
>>>>>> (gdb) bt
>>>>>> #0  0x00007f83ea215ae9 in syscall () from /lib64/libc.so.6
>>>>>> #1  0x00000000005bba35 in wait__ (e=0x2989390) at
>>>>>> pthread/ethr_event.c:92
>>>>>> #2  ethr_event_wait (e=0x2989390) at pthread/ethr_event.c:218
>>>>>> #3  0x00000000004ae5bd in erts_tse_wait (fcalls=<value optimized out>,
>>>>>> esdp=0x7f83e8e2c440, rq=0x7f83e9d5e7c0) at beam/erl_threads.h:2319
>>>>>> #4  scheduler_wait (fcalls=<value optimized out>, esdp=0x7f83e8e2c440,
>>>>>> rq=0x7f83e9d5e7c0) at beam/erl_process.c:2087
>>>>>> #5  0x00000000004afb94 in schedule (p=<value optimized out>,
>>>>>> calls=<value optimized out>) at beam/erl_process.c:6467
>>>>>> #6  0x0000000000539ca2 in process_main () at beam/beam_emu.c:1268
>>>>>> #7  0x00000000004b1279 in sched_thread_func (vesdp=0x7f83e8e2c440) at
>>>>>> beam/erl_process.c:4834
>>>>>> #8  0x00000000005bb3e6 in thr_wrapper (vtwd=0x7fffe8266da0) at
>>>>>> pthread/ethread.c:106
>>>>>> #9  0x00007f83ea6d3851 in start_thread () from /lib64/libpthread.so.0
>>>>>> #10 0x00007f83ea21911d in clone () from /lib64/libc.so.6
>>>>>> (gdb)
>>>>>>
>>>>>>
>>>>>> (gdb) bt
>>>>>> #0  0x00007f83ea6db09d in waitpid () from /lib64/libpthread.so.0
>>>>>> #1  0x0000000000555a9f in child_waiter (unused=<value optimized out>)
>>>>>> at sys/unix/sys.c:2700
>>>>>> #2  0x00000000005bb3e6 in thr_wrapper (vtwd=0x7fffe8266d50) at
>>>>>> pthread/ethread.c:106
>>>>>> #3  0x00007f83ea6d3851 in start_thread () from /lib64/libpthread.so.0
>>>>>> #4  0x00007f83ea21911d in clone () from /lib64/libc.so.6
>>>>>> (gdb)
>>>>>>
>>>>>>
>>>>>> **** END UPDATE ****
>>>>>>
>>>>>>
>>>>>> I'm happy to provide any information I can, so please don't hesitate to
>>>>>> ask.
>>>>>>
>>>>>> Thanks in advance!
>>>>>>
>>>>>> Kind Regards,
>>>>>>
>>>>>> Peter Membrey
>>>>>>
>>>> _______________________________________________
>>>> erlang-bugs mailing list
>>>> erlang-bugs@REDACTED
>>>> http://erlang.org/mailman/listinfo/erlang-bugs
>>