[ltt-dev] Tracing thread name (was: ltt comm tracking)
peterz at infradead.org
Mon Aug 3 10:28:27 EDT 2009
On Mon, 2009-08-03 at 09:48 -0400, Mathieu Desnoyers wrote:
> * 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:
> If I look at the man page:
> PR_SET_NAME (since Linux 2.6.9)
> Set the process name for the calling process, using the value in
> the location pointed to by (char *) arg2. The name can be up to
> 16 bytes long, and should be null terminated if it contains
> fewer bytes.
> It seems to officially set the process name, not thread name.
Then the man page is wrong, it really only sets the task (thread) name.
> 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.
> Ideally, having something like prctl PR_SET/GET_THREAD_NAME would
> probably make sense.
Going by the current behaviour, you'd need to add process name.
void set_task_comm(struct task_struct *tsk, char *buf)
strlcpy(tsk->comm, buf, sizeof(tsk->comm));
More information about the lttng-dev