linux-kernel - [PATCH v3 2/5] perf header: Write out even empty die_cpus

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Message-Id: <20241216232459.427642-3-irogers@google.com>
Date: Mon, 16 Dec 2024 15:24:56 -0800
From: Ian Rogers <irogers@...gle.com>
To: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...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>, 
	Kan Liang <kan.liang@...ux.intel.com>, Sun Haiyong <sunhaiyong@...ngson.cn>, 
	Yanteng Si <siyanteng@...ngson.cn>, linux-perf-users@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: [PATCH v3 2/5] perf header: Write out even empty die_cpus_list

Reading the CPU topology is tolerant to the dies_cpus_list being
missing by using the feature's size in the data file/pipe. However,
the feature's size is just the header size and may be
unaligned. Making the header size aligned breaks detecting a missing
die_cpus_list. To allow the header size to be aligned always write the
die_cpus_lists even if empty.

Signed-off-by: Ian Rogers <irogers@...gle.com>
---
 tools/perf/util/header.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index 048e563069bc..03e43a9894d4 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -628,9 +628,6 @@ static int write_cpu_topology(struct feat_fd *ff,
 			return ret;
 	}
 
-	if (!tp->die_cpus_lists)
-		goto done;
-
 	ret = do_write(ff, &tp->die_cpus_lists, sizeof(tp->die_cpus_lists));
 	if (ret < 0)
 		goto done;
-- 
2.47.1.613.gc27f4b7a9f-goog