[ltt-dev] Tracing thread name

[matthieu.castet@parrot.com (Matthieu CASTET)]

Hi Mathieu,

Mathieu Desnoyers a ?crit :
> * Matthieu CASTET (matthieu.castet at parrot.com) wrote:
>> Hi,
>>
>> I use ltt on a 2.6.27 on an arm architecture.
>> It works quite well, but I have a minor problem :
>>
>> my application sets thread name with prctl PR_SET_NAME. But ltt viewer
>> doesn't seem to saw it.
>>
> 
> Hrm, I guess we might want to instrument set_task_comm as you propose to
> get the correct process name, but if this gets us the thread name, I
> think it's only an implementation side-effect:

> The way LTTng handles thread names is by adding a userspace "thread
> branding" event. It should be executed at thread startup. The downside
> of the current LTTng approach is that we cannot know the name of threads
> already executing before we started tracing.
> 

Do you know if it is possible to patch my version to add such feature ?

I saw that the name already change in the trace before/after an exec.
How lltv get the new name ?
With "fs.exec" tracepoint ?
In that case I could fake a "fs.exec" tracepoint in set_task_comm.

Thanks

Matthieu