From: Arnaldo Carvalho de Melo <acme@redhat.com>

As it is just used to waste some cycles, not being used as all, to
silence some compilers.

Noticed with gcc version 16.0.1 20260115 on fedora 44:

    tests/sw-clock.c: In function '__test__sw_clock_freq':
    tests/sw-clock.c:31:22: error: variable 'tmp' set but not used [-Werror=unused-but-set-variable=]
       31 |         volatile int tmp = 0;
          |                      ^~~

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/perf/tests/sw-clock.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/tools/perf/tests/sw-clock.c b/tools/perf/tests/sw-clock.c
index 4a2ad7176fa07be0..b6e46975379cd5ef 100644
--- a/tools/perf/tests/sw-clock.c
+++ b/tools/perf/tests/sw-clock.c
@@ -5,6 +5,7 @@
 #include <stdlib.h>
 #include <signal.h>
 #include <sys/mman.h>
+#include <linux/compiler.h>
 #include <linux/string.h>
 
 #include "tests.h"
@@ -28,7 +29,7 @@
 static int __test__sw_clock_freq(enum perf_sw_ids clock_id)
 {
 	int i, err = -1;
-	volatile int tmp = 0;
+	volatile int tmp __maybe_unused = 0;
 	u64 total_periods = 0;
 	int nr_samples = 0;
 	char sbuf[STRERR_BUFSIZE];
-- 
2.52.0