linux-kernel - [PATCH] locking/rwsem: Move is_rwsem_reader_owned() and rwsem_owner() under CONFIG_DEBUG

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Message-ID: <20240909182905.161156-1-longman@redhat.com>
Date: Mon,  9 Sep 2024 14:29:05 -0400
From: Waiman Long <longman@...hat.com>
To: Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Will Deacon <will.deacon@....com>,
	Boqun Feng <boqun.feng@...il.com>
Cc: linux-kernel@...r.kernel.org,
	llvm@...ts.linux.dev,
	Nathan Chancellor <nathan@...nel.org>,
	Nick Desaulniers <ndesaulniers@...gle.com>,
	Bill Wendling <morbo@...gle.com>,
	Justin Stitt <justinstitt@...gle.com>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Waiman Long <longman@...hat.com>
Subject: [PATCH] locking/rwsem: Move is_rwsem_reader_owned() and rwsem_owner() under CONFIG_DEBUG_RWSEMS

Both is_rwsem_reader_owned() and rwsem_owner() are currently only used when
CONFIG_DEBUG_RWSEMS is defined. This causes a compilation error with clang
when `make W=1` and CONFIG_WERROR=y:

kernel/locking/rwsem.c:187:20: error: unused function 'is_rwsem_reader_owned' [-Werror,-Wunused-function]
  187 | static inline bool is_rwsem_reader_owned(struct rw_semaphore *sem)
      |                    ^~~~~~~~~~~~~~~~~~~~~
kernel/locking/rwsem.c:271:35: error: unused function 'rwsem_owner' [-Werror,-Wunused-function]
  271 | static inline struct task_struct *rwsem_owner(struct rw_semaphore *sem)
      |                                   ^~~~~~~~~~~

Fix this by moving these two functions under the CONFIG_DEBUG_RWSEMS define.

Reported-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Signed-off-by: Waiman Long <longman@...hat.com>
---
 kernel/locking/rwsem.c | 22 ++++++++++------------
 1 file changed, 10 insertions(+), 12 deletions(-)

diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c
index 33cac79e3994..4b041e9c408f 100644
--- a/kernel/locking/rwsem.c
+++ b/kernel/locking/rwsem.c
@@ -181,12 +181,21 @@ static inline void rwsem_set_reader_owned(struct rw_semaphore *sem)
 	__rwsem_set_reader_owned(sem, current);
 }
 
+#ifdef CONFIG_DEBUG_RWSEMS
+/*
+ * Return just the real task structure pointer of the owner
+ */
+static inline struct task_struct *rwsem_owner(struct rw_semaphore *sem)
+{
+	return (struct task_struct *)
+		(atomic_long_read(&sem->owner) & ~RWSEM_OWNER_FLAGS_MASK);
+}
+
 /*
  * Return true if the rwsem is owned by a reader.
  */
 static inline bool is_rwsem_reader_owned(struct rw_semaphore *sem)
 {
-#ifdef CONFIG_DEBUG_RWSEMS
 	/*
 	 * Check the count to see if it is write-locked.
 	 */
@@ -194,11 +203,9 @@ static inline bool is_rwsem_reader_owned(struct rw_semaphore *sem)
 
 	if (count & RWSEM_WRITER_MASK)
 		return false;
-#endif
 	return rwsem_test_oflags(sem, RWSEM_READER_OWNED);
 }
 
-#ifdef CONFIG_DEBUG_RWSEMS
 /*
  * With CONFIG_DEBUG_RWSEMS configured, it will make sure that if there
  * is a task pointer in owner of a reader-owned rwsem, it will be the
@@ -265,15 +272,6 @@ static inline bool rwsem_write_trylock(struct rw_semaphore *sem)
 	return false;
 }
 
-/*
- * Return just the real task structure pointer of the owner
- */
-static inline struct task_struct *rwsem_owner(struct rw_semaphore *sem)
-{
-	return (struct task_struct *)
-		(atomic_long_read(&sem->owner) & ~RWSEM_OWNER_FLAGS_MASK);
-}
-
 /*
  * Return the real task structure pointer of the owner and the embedded
  * flags in the owner. pflags must be non-NULL.
-- 
2.43.5