Merge tag 'locking-core-2022-10-07' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull locking updates from Ingo Molnar:

 - Disable preemption in rwsem_write_trylock()'s attempt to take the
   rwsem, to avoid RT tasks hogging the CPU, which managed to preempt
   this function after the owner has been cleared but before a new owner
   is set. Also add debug checks to enforce this.

 - Add __lockfunc to more slow path functions and add __sched to
   semaphore functions.

 - Mark spinlock APIs noinline when the respective CONFIG_INLINE_SPIN_*
   toggles are disabled, to reduce LTO text size.

 - Print more debug information when lockdep gets confused in
   look_up_lock_class().

 - Improve header file abuse checks.

 - Misc cleanups

* tag 'locking-core-2022-10-07' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  locking/lockdep: Print more debug information - report name and key when look_up_lock_class() got confused
  locking: Add __sched to semaphore functions
  locking/rwsem: Disable preemption while trying for rwsem lock
  locking: Detect includes rwlock.h outside of spinlock.h
  locking: Add __lockfunc to slow path functions
  locking/spinlocks: Mark spinlocks noinline when inline spinlocks are disabled
  selftests: futex: Fix 'the the' typo in comment

1 files changed, 12 insertions, 2 deletions

diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c
index 65f0262f635e..44873594de03 100644
--- a/kernel/locking/rwsem.c
+++ b/kernel/locking/rwsem.c
@@ -133,14 +133,19 @@
  * the owner value concurrently without lock. Read from owner, however,
  * may not need READ_ONCE() as long as the pointer value is only used
  * for comparison and isn't being dereferenced.
+ *
+ * Both rwsem_{set,clear}_owner() functions should be in the same
+ * preempt disable section as the atomic op that changes sem->count.
  */
 static inline void rwsem_set_owner(struct rw_semaphore *sem)
 {
+	lockdep_assert_preemption_disabled();
 	atomic_long_set(&sem->owner, (long)current);
 }
 
 static inline void rwsem_clear_owner(struct rw_semaphore *sem)
 {
+	lockdep_assert_preemption_disabled();
 	atomic_long_set(&sem->owner, 0);
 }
 
@@ -251,13 +256,16 @@ static inline bool rwsem_read_trylock(struct rw_semaphore *sem, long *cntp)
 static inline bool rwsem_write_trylock(struct rw_semaphore *sem)
 {
 	long tmp = RWSEM_UNLOCKED_VALUE;
+	bool ret = false;
 
+	preempt_disable();
 	if (atomic_long_try_cmpxchg_acquire(&sem->count, &tmp, RWSEM_WRITER_LOCKED)) {
 		rwsem_set_owner(sem);
-		return true;
+		ret = true;
 	}
 
-	return false;
+	preempt_enable();
+	return ret;
 }
 
 /*
@@ -1352,8 +1360,10 @@ static inline void __up_write(struct rw_semaphore *sem)
 	DEBUG_RWSEMS_WARN_ON((rwsem_owner(sem) != current) &&
 			    !rwsem_test_oflags(sem, RWSEM_NONSPINNABLE), sem);
 
+	preempt_disable();
 	rwsem_clear_owner(sem);
 	tmp = atomic_long_fetch_add_release(-RWSEM_WRITER_LOCKED, &sem->count);
+	preempt_enable();
 	if (unlikely(tmp & RWSEM_FLAG_WAITERS))
 		rwsem_wake(sem);
 }