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

Mon Jul 6 00:10:32 EDT 2015

This is how I am creating the session and using

lttng-relayd -o /var/tmp/lttng-traces -d

lttng-sessiond --consumerd32-path /usr/lib/lttng/libexec/lttng-consumerd
--consumerd32-libdir /usr/lib/ --consumerd64-path
/usr/lib64/lttng/libexec/lttng-consumerd --consumerd64-libdir /usr/lib64/
-b --no-kernel

lttng  --no-sessiond create mysession --live 2000000 -U net://128.0.0.4

lttng enable-channel mychannel --userspace --buffers-pid -s mysession
--tracefile-size 2000000 --tracefile-count 2

lttng enable-event --channel mychannel --userspace --all --exclude
'ust_libc:*' -s mysession

lttng start mysession

lttng list

At present, I am not trying to enable new channels. The above is pretty
much what I do.

On Sat, Jul 4, 2015 at 1:26 AM, Jérémie Galarneau <
jeremie.galarneau at efficios.com> wrote:

> 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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