linux-kernel - Re: [PATCH v4 3/3] perf/core: Check sample_type in perf_sample_save

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Message-ID: <20240515085840.GD40213@noisy.programming.kicks-ass.net>
Date: Wed, 15 May 2024 10:58:40 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Namhyung Kim <namhyung@...nel.org>
Cc: Yabin Cui <yabinc@...gle.com>, 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@...nel.org>, Ian Rogers <irogers@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
	bpf@...r.kernel.org
Subject: Re: [PATCH v4 3/3] perf/core: Check sample_type in
 perf_sample_save_brstack

On Fri, May 10, 2024 at 02:29:58PM -0700, Namhyung Kim wrote:
> On Fri, May 10, 2024 at 12:14 PM Yabin Cui <yabinc@...gle.com> wrote:
> >
> > Check sample_type in perf_sample_save_brstack() to prevent
> > saving branch stack data when it isn't required.
> >
> > Suggested-by: Namhyung Kim <namhyung@...nel.org>
> > Signed-off-by: Yabin Cui <yabinc@...gle.com>
> 
> It seems powerpc has the similar bug, then you need this:
> 
> Fixes: eb55b455ef9c ("perf/core: Add perf_sample_save_brstack() helper")

Is this really a bug? AFAICT it just does unneeded work, no?