linux-kernel - Re: [PATCH v1 2/8] tracing/ftrace: guard syscall probe with preempt

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Message-ID: <20241004105211.13ea45da@gandalf.local.home>
Date: Fri, 4 Oct 2024 10:52:11 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc: Masami Hiramatsu <mhiramat@...nel.org>, linux-kernel@...r.kernel.org,
 Peter Zijlstra <peterz@...radead.org>, Alexei Starovoitov <ast@...nel.org>,
 Yonghong Song <yhs@...com>, "Paul E . McKenney" <paulmck@...nel.org>, Ingo
 Molnar <mingo@...hat.com>, Arnaldo Carvalho de Melo <acme@...nel.org>, Mark
 Rutland <mark.rutland@....com>, Alexander Shishkin
 <alexander.shishkin@...ux.intel.com>, Namhyung Kim <namhyung@...nel.org>,
 Andrii Nakryiko <andrii.nakryiko@...il.com>, bpf@...r.kernel.org, Joel
 Fernandes <joel@...lfernandes.org>, linux-trace-kernel@...r.kernel.org,
 Michael Jeanson <mjeanson@...icios.com>
Subject: Re: [PATCH v1 2/8] tracing/ftrace: guard syscall probe with
 preempt_notrace

On Fri, 4 Oct 2024 10:19:36 -0400
Mathieu Desnoyers <mathieu.desnoyers@...icios.com> wrote:

> The eBPF people want to leverage this. When I last discussed this with
> eBPF maintainers, they were open to adapt eBPF after this infrastructure
> series is merged. Based on this eBPF attempt from 2022:
> 
> https://lore.kernel.org/lkml/c323bce9-a04e-b1c3-580a-783fde259d60@fb.com/

Sorry, I wasn't part of that discussion.

> 
> The sframe code is just getting in shape (2024), but is far from being ready.
> 
> Everyone appears to be waiting for this infrastructure work to go in
> before they can build on top. Once this infrastructure is available,
> multiple groups can start working on introducing use of this into their
> own code in parallel.
> 
> Four years into this effort, and this is the first time we're told we need
> to adapt in-tree tracers to handle the page faults before this can go in.
> 
> Could you please stop moving the goal posts ?

I don't think I'm moving the goal posts. I was mentioning to show an
in-tree user. If BPF wants this, I'm all for it. The only thing I saw was a
generalization in the cover letter about perf, bpf and ftrace using
faultible tracepoints. I just wanted to see a path for that happening.

-- Steve