[tip: locking/core] rust: helpers: Avoid raw_spin_lock initialization for PREEMPT_RT

From: tip-bot2 for Eder Zulian
Date: Mon Nov 11 2024 - 05:58:13 EST


The following commit has been merged into the locking/core branch of tip:

Commit-ID: 5c2e7736e20d9b348a44cafbfa639fe2653fbc34
Gitweb: https://git.kernel.org/tip/5c2e7736e20d9b348a44cafbfa639fe2653fbc34
Author: Eder Zulian <ezulian@xxxxxxxxxx>
AuthorDate: Thu, 07 Nov 2024 17:32:23 +01:00
Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Mon, 11 Nov 2024 11:49:46 +01:00

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.")
Closes: https://lore.kernel.org/oe-kbuild-all/202409251238.vetlgXE9-lkp@xxxxxxxxx/
Reported-by: kernel test robot <lkp@xxxxxxxxx>
Signed-off-by: Eder Zulian <ezulian@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Reviewed-by: Boqun Feng <boqun.feng@xxxxxxxxx>
Tested-by: Boqun Feng <boqun.feng@xxxxxxxxx>
Link: https://lore.kernel.org/r/20241107163223.2092690-2-ezulian@xxxxxxxxxx
---
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 f9f14e1..f6499c3 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 acc1376..92f7fc4 100644
--- a/rust/helpers/spinlock.c
+++ b/rust/helpers/spinlock.c
@@ -7,10 +7,14 @@ 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)