From: Cédric Le Goater <clg@redhat.com>

Newer gcc compiler (version 16.0.0 20260103 (Red Hat 16.0.0-0) (GCC))
detects an unused variable error:

  ../tests/unit/rcutorture.c: In function ‘rcu_read_stress_test’:
  ../tests/unit/rcutorture.c:251:18: error: variable ‘garbage’ set but not used [-Werror=unused-but-set-variable=]
    251 |     volatile int garbage = 0;
        |                  ^~~~~~~

Since the 'garbage' variable is used to generate memory reads from the
CPU while holding the RCU lock, it can not be removed. Tag it as
((unused)) instead to silence the compiler warnings/errors.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Link: https://lore.kernel.org/qemu-devel/20260112163350.1251114-1-clg@redhat.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>
(cherry picked from commit 7a05be8c70bb789c23076b1ca2563ed7d87c6fb8)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

diff --git a/tests/unit/rcutorture.c b/tests/unit/rcutorture.c
index 7662081683..2f19d479a3 100644
--- a/tests/unit/rcutorture.c
+++ b/tests/unit/rcutorture.c
@@ -248,7 +248,7 @@ static void *rcu_read_stress_test(void *arg)
     int pc;
     long long n_reads_local = 0;
     long long rcu_stress_local[RCU_STRESS_PIPE_LEN + 1] = { 0 };
-    volatile int garbage = 0;
+    volatile int garbage __attribute__ ((unused)) = 0;
 
     rcu_register_thread();
 
-- 
2.47.3