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

Loïc Hoguin <>
Fri Nov 23 01:49:31 CET 2012


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 <>
> Date: 22 November 2012 19:02
> Subject: VM locks up on write to socket (and now it seems to file too)
> To: 
>
>
> 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
>


-- 
Loïc Hoguin
Erlang Cowboy
Nine Nines
http://ninenines.eu


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