linux-kernel - Re: [PATCH v5 0/8] Faultable Tracepoints

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Date: Wed, 26 Jun 2024 21:25:43 -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>, Jiri Olsa <jolsa@...hat.com>,
 Namhyung Kim <namhyung@...nel.org>, bpf@...r.kernel.org, Joel Fernandes
 <joel@...lfernandes.org>
Subject: Re: [PATCH v5 0/8] Faultable Tracepoints

On Wed, 26 Jun 2024 14:59:33 -0400
Mathieu Desnoyers <mathieu.desnoyers@...icios.com> wrote:

> Wire up the system call tracepoints with Tasks Trace RCU to allow
> the ftrace, perf, and eBPF tracers to handle page faults.
> 
> This series does the initial wire-up allowing tracers to handle page
> faults, but leaves out the actual handling of said page faults as future
> work.
> 
> I have tested this against a feature branch of lttng-modules which
> implements handling of page faults for the filename argument of the
> openat(2) system call.
> 
> This v5 addresses comments from the previous round of review [1].

Hi Mathieu,

Can you resend this and Cc linux-trace-kernel@...r.kernel.org?

That would put it into our patchwork and makes it work with our workflow.

 https://patchwork.kernel.org/project/linux-trace-kernel/list/

Thanks,

-- Steve

> 
> Steven Rostedt suggested separating tracepoints into two separate
> sections. It is unclear how that approach would prove to be an
> improvement over the currently proposed approach, so those changes were
> not incorporated. See [2] for my detailed reply.
> 
> In the previous round, Peter Zijlstra suggested use of SRCU rather than
> Tasks Trace RCU. See my reply about the distinction between SRCU and
> Tasks Trace RCU [3] and this explanation from Paul E. McKenney about the
> purpose of Tasks Trace RCU [4].
> 
> The macros DEFINE_INACTIVE_GUARD and activate_guard are added to
> cleanup.h for use in the __DO_TRACE() macro. Those appear to be more
> flexible than the guard_if() proposed by Peter Zijlstra in the previous
> round of review [5].
> 
> This series is based on kernel v6.9.6.