static_call: Fix unused variable warn w/o MODULE

stable inclusion
from stable-5.10.63
commit b1075d2a705266a9051857810e0d2ac55a9e232f
bugzilla: 182231 https://gitee.com/openeuler/kernel/issues/I4EFS1

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b1075d2a705266a9051857810e0d2ac55a9e232f

--------------------------------

commit 7d95f227 upstream.

Here is the warning converted as error and reported by GCC:

  kernel/static_call.c: In function ‘__static_call_update’:
  kernel/static_call.c:153:18: error: unused variable ‘mod’ [-Werror=unused-variable]
    153 |   struct module *mod = site_mod->mod;
        |                  ^~~
  cc1: all warnings being treated as errors
  make[1]: *** [scripts/Makefile.build:271: kernel/static_call.o] Error 1

This is simply because since recently, we no longer use 'mod' variable
elsewhere if MODULE is unset.

When using 'make tinyconfig' to generate the default kconfig, MODULE is
unset.

There are different ways to fix this warning. Here I tried to minimised
the number of modified lines and not add more #ifdef. We could also move
the declaration of the 'mod' variable inside the if-statement or
directly use site_mod->mod.

Fixes: 698bacef ("static_call: Align static_call_is_init() patching condition")
Signed-off-by: NMatthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210326105023.2058860-1-matthieu.baerts@tessares.netSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Acked-by: NWeilong Chen <chenweilong@huawei.com>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

kernel/static_call.c

@@ -165,13 +165,13 @@ void __static_call_update(struct static_call_key *key, void *tramp, void *func)
 
 		stop = __stop_static_call_sites;
 
-#ifdef CONFIG_MODULES
 		if (mod) {
+#ifdef CONFIG_MODULES
 			stop = mod->static_call_sites +
 			       mod->num_static_call_sites;
 			init = mod->state == MODULE_STATE_COMING;
-		}
 #endif
+		}
 
 		for (site = site_mod->sites;
 		     site < stop && static_call_key(site) == key; site++) {