linux-kernel - Re: [RFC PATCH 4/5] tracing: Remove conditional locking from __DO

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Message-ID: <CAHk-=whTjKsV5jYyq5yAxn7msQuyFdr9LB1vXcF6dOw2tubkWA@mail.gmail.com>
Date: Sat, 23 Nov 2024 09:38:33 -0800
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc: Steven Rostedt <rostedt@...dmis.org>, linux-kernel@...r.kernel.org, 
	Thomas Gleixner <tglx@...utronix.de>, Michael Jeanson <mjeanson@...icios.com>, 
	Masami Hiramatsu <mhiramat@...nel.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>, Jordan Rife <jrife@...gle.com>, 
	linux-trace-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 4/5] tracing: Remove conditional locking from __DO_TRACE()

On Sat, 23 Nov 2024 at 07:31, Mathieu Desnoyers
<mathieu.desnoyers@...icios.com> wrote:
>
>  include/linux/tracepoint.h | 45 ++++++++++----------------------------
>  1 file changed, 12 insertions(+), 33 deletions(-)

Thanks. This looks much more straightforward, and obviously is smaller too.

Side note: I realize I was the one suggesting "scoped_guard()", but
looking at the patch I do think that just unnecessarily added another
level of indentation. Since you already wrote the

    if (cond) {
        ..
    }

part as a block statement, there's no upside to the guard having its
own scoped block, so instead of

    if (cond) { \
        scoped_guard(preempt_notrace)           \
            __DO_TRACE_CALL(name, TP_ARGS(args)); \
    }

this might be simpler as just a plain "guard()" and one less indentation:

    if (cond) { \
        guard(preempt_notrace);           \
        __DO_TRACE_CALL(name, TP_ARGS(args)); \
    }

but by now this is just an unimportant detail.

I think I suggested scoped_guard() mainly because that would then just
make the "{ }" in the if-statement superfluous, but that's such a
random reason that it *really* doesn't matter.

             Linus