linux-kernel - [RFC PATCH 09/13] klist.h: Fix parentheses around macro parameter use

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Date:   Thu,  4 May 2023 16:05:23 -0400
From:   Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Tejun Heo <htejun@...il.com>,
        Peter Zijlstra <peterz@...radead.org>
Subject: [RFC PATCH 09/13] klist.h: Fix parentheses around macro parameter use

Add missing parentheses around "_name" parameter use in KLIST_INIT().
It keeps list macros consistent, and prevents unexpected operator
precedence situations, for example:

  struct klist a[1] = { KLIST_INIT(*a, NULL, NULL) };

Where the "." operator within KLIST_INIT() is evaluated before the "*"
operator.

Add missing parentheses around macro parameter use in the following
patterns to ensure operator precedence behaves as expected:

- "x = y" is changed for "x = (y)", because "y" can be an expression
  containing a comma if it is the result of the expansion of a macro such
  as #define eval(...) __VA_ARGS__, which would cause unexpected operator
  precedence. This use-case is far-fetched, but we have to choose one
  way or the other (with or without parentheses) for consistency.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Tejun Heo <htejun@...il.com>
Cc: Peter Zijlstra <peterz@...radead.org>
---
 include/linux/klist.h | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/include/linux/klist.h b/include/linux/klist.h
index b0f238f20dbb..d7e0612ca4ff 100644
--- a/include/linux/klist.h
+++ b/include/linux/klist.h
@@ -23,10 +23,10 @@ struct klist {
 } __attribute__ ((aligned (sizeof(void *))));
 
 #define KLIST_INIT(_name, _get, _put)					\
-	{ .k_lock	= __SPIN_LOCK_UNLOCKED(_name.k_lock),		\
-	  .k_list	= LIST_HEAD_INIT(_name.k_list),			\
-	  .get		= _get,						\
-	  .put		= _put, }
+	{ .k_lock	= __SPIN_LOCK_UNLOCKED((_name).k_lock),		\
+	  .k_list	= LIST_HEAD_INIT((_name).k_list),		\
+	  .get		= (_get),					\
+	  .put		= (_put), }
 
 #define DEFINE_KLIST(_name, _get, _put)					\
 	struct klist _name = KLIST_INIT(_name, _get, _put)
-- 
2.25.1