[lttng-dev] Valgrind Memory Error in lttng-relayd

Fri Jul 3 15:56:47 EDT 2015

Can you share a bit more information about the session configurations in
your use case?
Are you creating and destroying new sessions, tracing in per-pid or uid
mode, enabling new channels, etc.

Also, is this in "live" mode or are you just streaming to the relay daemon?
(lttng create --set-url net://somewhere)

Jérémie

On Fri, Jul 3, 2015 at 3:30 PM, Jérémie Galarneau <
jeremie.galarneau at efficios.com> wrote:

>
>
> On Fri, Jul 3, 2015 at 1:48 PM, Aravind HT <aravind.ht at gmail.com> wrote:
>
>> Hi,
>>
>> Thanks for replying.
>>
>> I have a daemon which i'm using for some CLI application, this forks
>> whenever invoked but never exec()'s and am using lttng for tracing this and
>> a few other apps.
>> I have a script that I run to stress test this daemon; this I think means
>> lttng is also being stressed.
>> As soon as I run this script, after a few streams are created, I
>> sometimes see a soft hang as mentioned in my previous thread
>> http://lists.lttng.org/pipermail/lttng-dev/2015-May/024533.html
>> or
>> I see lttng-relayd coring.
>>
>> In short, an app that calls quite a bit of fork and exits which is being
>> traced with other normal apps that run forever should re-create the problem.
>>
>> To run valgrind, use the -DVALGRIND when building, your can grep the code
>> for what this does.
>> Kill the valgrind  proc with -TERM to produce the logs.
>>
>>
> Doh, of course! :-)
>
>
>> This is the command and the options that I use to run valgrind
>>
>> valgrind --tool=memcheck --leak-check=full -v --log-file=/tmp/test
>> --trace-children=yes  /usr/bin/lttng-relayd -o /var/log/lttng-traces -d
>>
>>
>>
>> I have tried the fix detailed in the checkin
>> http://git.lttng.org/?p=lttng-tools.git;a=commitdiff;h=cd2ef1ef1d54ced9e4d0d03b865bb7fc6a905f80
>>
>> and it seems to work for me. This however only solves the relayd core,
>> but I still see the "soft hang" happening.
>>
>
>> Can some one please tell me how the above fix is missing from the source ?
>>
>
> Somehow it appears this was reverted by this commit:
>
> https://github.com/lttng/lttng-tools/commit/1dc0526df43f2b5f86ef451e4c0331445346b15f
>
> I'm trying to reproduce the problem here.
>
> Jérémie
>
>
>>
>> Regards,
>>
>> Aravind.
>>
>>
>>
>>
>> On Fri, Jul 3, 2015 at 8:36 PM, Jérémie Galarneau <
>> jeremie.galarneau at efficios.com> wrote:
>>
>>> Hi,
>>>
>>> Thanks for the detailed report. Can you provide a sequence of steps that
>>> leads to this problem?
>>> Also, did you modify lttng-relayd at all to be able to run valgrind? I
>>> seem to remember valgrind not supporting clone().
>>>
>>> Thanks,
>>> Jérémie
>>>
>>> On Thu, Jul 2, 2015 at 12:42 PM, Aravind HT <aravind.ht at gmail.com>
>>> wrote:
>>>
>>>> Possible Solution :
>>>>
>>>> The following changes seem to be missing from the actual code
>>>>
>>>>
>>>> http://git.lttng.org/?p=lttng-tools.git;a=commitdiff;h=cd2ef1ef1d54ced9e4d0d03b865bb7fc6a905f80
>>>>
>>>>
>>>> only the connection.h changes have been absorbed, while the main.c
>>>> changes left out.
>>>>
>>>> On Mon, Jun 29, 2015 at 11:51 PM, Aravind HT <aravind.ht at gmail.com>
>>>> wrote:
>>>>
>>>>> Hi,
>>>>>
>>>>> I ran valgrind on lttng-relayd for a soft hang issue that I had
>>>>> reported earlier.
>>>>> http://lists.lttng.org/pipermail/lttng-dev/2015-May/024533.html
>>>>>
>>>>> Below are the list of errors that I found.
>>>>>
>>>>> ==793== Thread 4:
>>>>> ==793== Invalid write of size 8
>>>>> ==793==    at 0x406038: cds_list_add (list.h:53)
>>>>> ==793==    by 0x409442: queue_stream (main.c:1175)
>>>>> ==793==    by 0x409AB7: relay_add_stream (main.c:1274)
>>>>> ==793==    by 0x40C47A: relay_process_control (main.c:2099)
>>>>> ==793==    by 0x40DBB1: relay_thread_worker (main.c:2574)
>>>>> ==793==    by 0x5BDAFE2: start_thread (pthread_create.c:312)
>>>>> ==793==    by 0x5ED8AFC: clone (clone.S:111)
>>>>> ==793==  Address 0x6e09040 is 64 bytes inside a block of size 312
>>>>> free'd
>>>>> ==793==    at 0x4C2898C: free (in
>>>>> /usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so)
>>>>> ==793==    by 0x418EF8: rcu_destroy_stream (stream.c:33)
>>>>> ==793==    by 0x5079C94: ??? (in /usr/lib64/liburcu.so.2.0.0)
>>>>> ==793==    by 0x5BDAFE2: start_thread (pthread_create.c:312)
>>>>> ==793==    by 0x5ED8AFC: clone (clone.S:111)
>>>>> ==793==
>>>>>
>>>>> Are there any known bugs/fixes for these ?
>>>>>
>>>>>
>>>>> Regards,
>>>>> Aravind.
>>>>>
>>>>>
>>>>
>>>> _______________________________________________
>>>> lttng-dev mailing list
>>>> lttng-dev at lists.lttng.org
>>>> http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
>>>>
>>>>
>>>
>>>
>>> --
>>> Jérémie Galarneau
>>> EfficiOS Inc.
>>> http://www.efficios.com
>>>
>>
>>
>
>
> --
> Jérémie Galarneau
> EfficiOS Inc.
> http://www.efficios.com
>

-- 
Jérémie Galarneau
EfficiOS Inc.
http://www.efficios.com
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