Re: [PATCH v3] trace-cmd: Stop recording when processes traced with -P exit

[Bijan Tabatabai <bijan311@gmail.com>]

I just tried that and discovered an interesting problem.
After the first sleep ended, my computer completely locked up, and
after a few minutes I decided to reset my computer.
Then after rebooting, I checked out the master branch, recompiled, and
tried running the same set of commands again.
This time, my computer locked up shortly after I pressed Ctrl+C after
both sleeps exited.
I am running Ubuntu 20.04 with Ubuntu's version of the 5.4 kernel.

Is this a bug that has been reported before? If not, what is the
process for "officially" reporting it?

Thank,
Bijan

On Wed, May 13, 2020 at 3:16 PM Steven Rostedt <rostedt@goodmis.org> wrote:
>
> On Wed, 13 May 2020 12:05:29 -0500
> Bijan Tabatabai <bijan311@gmail.com> wrote:
>
> > From: Bijan Tabatabai <bijan311@yahoo.com>
> >
> > When the -F flag is used in trace-cmd record, trace-cmd stops recording
> > when the executable it is tracing terminates.
> > This patch makes the -P flag act similarly.
> >
> > Signed-off-by: Bijan Tabatabai <bijan311@yahoo.com>
> > ---
> >  This patch has changed to use the pidfd interface to determine if a process
> >  has ended.
> >  It also has changed to work with the patch "trace-cmd: Handle filtered PIDs per
> >  ftarce instance" (5502bcef0f962cda).
> > ---
> >  tracecmd/include/trace-local.h |  2 +
> >  tracecmd/trace-record.c        | 84 ++++++++++++++++++++++++++++++++++
> >  2 files changed, 86 insertions(+)
> >
>
> Nice!
>
> Although I just tried it out and noticed that if I run the following
> command:
>
>  # sleep 20& sleep 50&
> [1] 2216
> [2] 2218
>  # trace-cmd record -e sched -P 2216 -B foo -e all -P 2218
>
> It will exit out after the first sleep (20 second) and before the second is
> done.
>
> It appears to exit as soon as the first process is finished. We should want
> to wait till the last one is finished.
>
> -- Steve