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

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Message-ID: <0ed11f00-d885-482a-8c82-37f9ffdb2968@efficios.com>
Date: Sun, 24 Nov 2024 20:50:12 -0500
From: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To: Linus Torvalds <torvalds@...ux-foundation.org>,
 Steven Rostedt <rostedt@...dmis.org>
Cc: 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 2024-11-23 12:38, Linus Torvalds wrote:
> 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.

Thanks for the follow up. I agree that guard() would remove one level
of nesting and would be an improvement.

Steven, do you want me to update the series with this change or
should I leave the scoped_guard() as is considering the ongoing
testing in linux-next ? We can always keep this minor change
(scoped_guard -> guard) for a follow up patch.

Thanks,

Mathieu

-- 
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com