linux-kernel - Re: [PATCH] exit: add trace_task_exit() tracepoint before current->mm is reset

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Message-ID: <Z-0RIXmHHGrXb5HH@krava>
Date: Wed, 2 Apr 2025 12:27:45 +0200
From: Jiri Olsa <olsajiri@...il.com>
To: Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc: Steven Rostedt <rostedt@...dmis.org>,
	Andrii Nakryiko <andrii@...nel.org>,
	linux-trace-kernel@...r.kernel.org, peterz@...radead.org,
	mingo@...nel.org, bpf@...r.kernel.org, linux-kernel@...r.kernel.org,
	kernel-team@...a.com, mhocko@...nel.org, oleg@...hat.com,
	brauner@...nel.org, glider@...gle.com, mhiramat@...nel.org,
	mathieu.desnoyers@...icios.com, akpm@...ux-foundation.org
Subject: Re: [PATCH] exit: add trace_task_exit() tracepoint before
 current->mm is reset

On Tue, Apr 01, 2025 at 03:17:01PM -0700, Andrii Nakryiko wrote:
> On Tue, Apr 1, 2025 at 3:12 PM Steven Rostedt <rostedt@...dmis.org> wrote:
> >
> > On Tue, 1 Apr 2025 15:04:11 -0700
> > Andrii Nakryiko <andrii.nakryiko@...il.com> wrote:
> >
> > > How bad would it be to just move trace_sched_process_exit() then? (and
> > > add group_dead there, as you mentioned)?
> >
> > I personally don't have an issue with that. In fact, the one place I used
> > the sched_process_exit tracepoint, I had to change to use
> > sched_process_free because it does too much after that.
> 
> heh, I ran into that as well just recently and also had to use
> sched_process_free instead of sched_process_exit, because between exit
> and free we still can get sched_switch tracepoint trigger (so it's a
> bit too early to clean up whatever per-task state I maintain in BPF
> program).
> 
> So yeah, I'm up for that as well, will send v2 just moving and
> extending the existing tracepoint. Thanks!

+1, it'd be great to have the group_dead info, we also need
to have some workarounds for that

thanks,
jirka

> 
> >
> > OK, let's just move the sched_process_exit tracepoint. It's in an arbitrary
> > location anyway.
> >
> > -- Steve
>