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

[Aravind HT]

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.

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 ?


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
>
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