linux-kernel - [PATCH v3 1/1] rust: helpers: Avoid raw_spin_lock initialization for PREEMPT

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Message-ID: <20241107163223.2092690-2-ezulian@redhat.com>
Date: Thu,  7 Nov 2024 17:32:23 +0100
From: Eder Zulian <ezulian@...hat.com>
To: linux-kernel@...r.kernel.org,
	linux-next@...r.kernel.org,
	rust-for-linux@...r.kernel.org
Cc: miguel.ojeda.sandonis@...il.com,
	tglx@...utronix.de,
	williams@...hat.com,
	ojeda@...nel.org,
	alex.gaynor@...il.com,
	gary@...yguo.net,
	bjorn3_gh@...tonmail.com,
	benno.lossin@...ton.me,
	a.hindborg@...nel.org,
	aliceryhl@...gle.com,
	tmgross@...ch.edu,
	jlelli@...hat.com,
	peterz@...radead.org,
	mingo@...hat.com,
	will@...nel.org,
	longman@...hat.com,
	boqun.feng@...il.com,
	bigeasy@...utronix.de,
	sfr@...b.auug.org.au,
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Subject: [PATCH v3 1/1] rust: helpers: Avoid raw_spin_lock initialization for PREEMPT_RT

When PREEMPT_RT=y, spin locks are mapped to rt_mutex types, so using
spinlock_check() + __raw_spin_lock_init() to initialize spin locks is
incorrect, and would cause build errors.

Introduce __spin_lock_init() to initialize a spin lock with lockdep
rquired information for PREEMPT_RT builds, and use it in the Rust
helper.

Fixes: d2d6422f8bd1 ("x86: Allow to enable PREEMPT_RT.")
Reported-by: kernel test robot <lkp@...el.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202409251238.vetlgXE9-lkp@intel.com/
Signed-off-by: Eder Zulian <ezulian@...hat.com>
---
V1 -> V2: Cleaned up style and addressed review comments
V2 -> V3: Improved commit title and description and corrected the 'Fixed:'
tag as per reviewer's suggestion

 include/linux/spinlock_rt.h | 15 +++++++--------
 rust/helpers/spinlock.c     |  8 ++++++--
 2 files changed, 13 insertions(+), 10 deletions(-)

diff --git a/include/linux/spinlock_rt.h b/include/linux/spinlock_rt.h
index f9f14e135be7..f6499c37157d 100644
--- a/include/linux/spinlock_rt.h
+++ b/include/linux/spinlock_rt.h
@@ -16,22 +16,21 @@ static inline void __rt_spin_lock_init(spinlock_t *lock, const char *name,
 }
 #endif
 
-#define spin_lock_init(slock)					\
+#define __spin_lock_init(slock, name, key, percpu)		\
 do {								\
-	static struct lock_class_key __key;			\
-								\
 	rt_mutex_base_init(&(slock)->lock);			\
-	__rt_spin_lock_init(slock, #slock, &__key, false);	\
+	__rt_spin_lock_init(slock, name, key, percpu);		\
 } while (0)
 
-#define local_spin_lock_init(slock)				\
+#define _spin_lock_init(slock, percpu)				\
 do {								\
 	static struct lock_class_key __key;			\
-								\
-	rt_mutex_base_init(&(slock)->lock);			\
-	__rt_spin_lock_init(slock, #slock, &__key, true);	\
+	__spin_lock_init(slock, #slock, &__key, percpu);	\
 } while (0)
 
+#define spin_lock_init(slock)		_spin_lock_init(slock, false)
+#define local_spin_lock_init(slock)	_spin_lock_init(slock, true)
+
 extern void rt_spin_lock(spinlock_t *lock) __acquires(lock);
 extern void rt_spin_lock_nested(spinlock_t *lock, int subclass)	__acquires(lock);
 extern void rt_spin_lock_nest_lock(spinlock_t *lock, struct lockdep_map *nest_lock) __acquires(lock);
diff --git a/rust/helpers/spinlock.c b/rust/helpers/spinlock.c
index b7b0945e8b3c..5971fdf6f755 100644
--- a/rust/helpers/spinlock.c
+++ b/rust/helpers/spinlock.c
@@ -6,10 +6,14 @@ void rust_helper___spin_lock_init(spinlock_t *lock, const char *name,
 				  struct lock_class_key *key)
 {
 #ifdef CONFIG_DEBUG_SPINLOCK
+# if defined(CONFIG_PREEMPT_RT)
+	__spin_lock_init(lock, name, key, false);
+# else /*!CONFIG_PREEMPT_RT */
 	__raw_spin_lock_init(spinlock_check(lock), name, key, LD_WAIT_CONFIG);
-#else
+# endif /* CONFIG_PREEMPT_RT */
+#else /* !CONFIG_DEBUG_SPINLOCK */
 	spin_lock_init(lock);
-#endif
+#endif /* CONFIG_DEBUG_SPINLOCK */
 }
 
 void rust_helper_spin_lock(spinlock_t *lock)
-- 
2.47.0