[erlang-bugs] VM locks up on write to socket (and now it seems to file too)
Patrik Nyblom
pan@REDACTED
Fri Nov 23 17:13:17 CET 2012
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
>>
>
>
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