linux-kernel - [PATCH] locking/local_lock: fix shadowing in __local_lock

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Message-Id: <20250923-local_lock_internal_fix_shadow-v1-1-14e313c88a46@kernel.org>
Date: Tue, 23 Sep 2025 23:02:45 +0900
From: Vincent Mailhol <mailhol@...nel.org>
To: Vlastimil Babka <vbabka@...e.cz>, Shakeel Butt <shakeel.butt@...ux.dev>, 
 Sebastian Andrzej Siewior <bigeasy@...utronix.de>, 
 Alexei Starovoitov <ast@...nel.org>, 
 Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org, Vincent Mailhol <mailhol@...nel.org>
Subject: [PATCH] locking/local_lock: fix shadowing in
 __local_lock_acquire()

The __local_lock_acquire() macro uses a local variable named 'l'. This
being a common name, there is a risk of shadowing other variables.

For example, it is currently shadowing the parameter 'l' of the:

  class_##_name##_t class_##_name##_constructor(_type *l)

function factory from linux/cleanup.h.

Both sparse (with default options) and GCC (with W=2 option) warn
about this shadowing.

This is a bening warning, but because the issue appears in a header,
it is spamming whoever is using it. So better to fix to remove some
noise.

Rename the variable from 'l' to '__lock' (with two underscore prefixes
as suggested in the Linux kernel coding style [1]) in order to prevent
the name collision.

For consistency, also rename 'tl' to '__trylock'.

[1] https://www.kernel.org/doc/html/latest/process/coding-style.html#macros-enums-and-rtl

Signed-off-by: Vincent Mailhol <mailhol@...nel.org>
---
I did not include a Fixes tag because I do not think that this is
worth backporting. But if you do mind, there it is:

Fixes: 51339d99c013 ("locking/local_lock, mm: replace localtry_ helpers with local_trylock_t type")
---
 include/linux/local_lock_internal.h | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/include/linux/local_lock_internal.h b/include/linux/local_lock_internal.h
index d80b5306a2c0ccf95a3405b6b947b5f1f9a3bd38..69feb161c5e6c94e36ba30b2c625eac0065d1e3d 100644
--- a/include/linux/local_lock_internal.h
+++ b/include/linux/local_lock_internal.h
@@ -96,18 +96,18 @@ do {								\
 
 #define __local_lock_acquire(lock)					\
 	do {								\
-		local_trylock_t *tl;					\
-		local_lock_t *l;					\
+		local_trylock_t *__trylock;				\
+		local_lock_t *__lock;					\
 									\
-		l = (local_lock_t *)(lock);				\
-		tl = (local_trylock_t *)l;				\
+		__lock = (local_lock_t *)(lock);			\
+		__trylock = (local_trylock_t *)__lock;			\
 		_Generic((lock),					\
 			local_trylock_t *: ({				\
-				lockdep_assert(tl->acquired == 0);	\
-				WRITE_ONCE(tl->acquired, 1);		\
+				lockdep_assert(__trylock->acquired == 0);\
+				WRITE_ONCE(__trylock->acquired, 1);	\
 			}),						\
 			local_lock_t *: (void)0);			\
-		local_lock_acquire(l);					\
+		local_lock_acquire(__lock);				\
 	} while (0)
 
 #define __local_lock(lock)					\

---
base-commit: cec1e6e5d1ab33403b809f79cd20d6aff124ccfe
change-id: 20250923-local_lock_internal_fix_shadow-2e2a24e95e76

Best regards,
-- 
Vincent Mailhol <mailhol@...nel.org>