linux-kernel - [PATCH] libperf: Add back guard on MAX_NR

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Message-ID: <8c8553387ebf904a9e5a93eaf643cb01164d9fb3.1736188471.git.christophe.leroy@csgroup.eu>
Date: Mon,  6 Jan 2025 20:38:28 +0100
From: Christophe Leroy <christophe.leroy@...roup.eu>
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>,
	"Liang, Kan" <kan.liang@...ux.intel.com>,
	Leo Yan <leo.yan@....com>
Cc: Christophe Leroy <christophe.leroy@...roup.eu>,
	linux-perf-users@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: [PATCH] libperf: Add back guard on MAX_NR_CPUS

Building perf with EXTRA_CFLAGS="-DMAX_NR_CPUS=1" fails:

	  CC      /home/chleroy/linux-powerpc/tools/perf/libperf/cpumap.o
	cpumap.c:16: error: "MAX_NR_CPUS" redefined [-Werror]
	   16 | #define MAX_NR_CPUS 4096
	      |
	<command-line>: note: this is the location of the previous definition

Commit e8399d34d568 ("libperf cpumap: Hide/reduce scope of MAX_NR_CPUS")
moved definition of MAX_NR_CPUS from lib/perf/include/internal/cpumap.h
to lib/perf/cpumap.c but the guard surrounding that definition got lost
in the move.

See commit 21b8732eb447 ("perf tools: Allow overriding MAX_NR_CPUS at
compile time") to see why it is needed.

Note that MAX_NR_CPUS was initialy defined in perf/perf.h and a
redundant definition was added by commit 9c3516d1b850 ("libperf:
Add perf_cpu_map__new()/perf_cpu_map__read() functions").

A cleaner fix would be to remove that duplicate but for the time
being fix the problem by bringing back the guard for when MAX_NR_CPUS
is already defined.

Fixes: e8399d34d568 ("libperf cpumap: Hide/reduce scope of MAX_NR_CPUS")
Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
Reviewed-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 tools/lib/perf/cpumap.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/tools/lib/perf/cpumap.c b/tools/lib/perf/cpumap.c
index fcc47214062a..12eaa6955121 100644
--- a/tools/lib/perf/cpumap.c
+++ b/tools/lib/perf/cpumap.c
@@ -13,7 +13,9 @@
 #include "internal.h"
 #include <api/fs/fs.h>
 
+#ifndef MAX_NR_CPUS
 #define MAX_NR_CPUS 4096
+#endif
 
 void perf_cpu_map__set_nr(struct perf_cpu_map *map, int nr_cpus)
 {
-- 
2.47.0