Re: linux-next: boot warning from the final tree

[Waiman Long]

On 11/21/25 5:33 PM, Boqun Feng wrote:
> Subject: [PATCH] locking/mutex: Initialize mutex::magic even when LOCKDEP=n
>
> When DEBUG_MUTEXES=y and LOCKDEP=n, mutex_lock() still checks on
> ->magic, hence debug_mutex_init() should be called in
> mutex_init_generic() as well. While we are at it, decouple LOCKDEP
> logic from debug_mutex_init(), because in this way debug_mutex_init()
> only needs one parameter, and we now have mutex_init_lockep() for
> LOCKDEP=y scenarios.
>
> Reported-by: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>
> Closes: https://lore.kernel.org/lkml/20251117202214.4f710f02@xxxxxxxxxxxxxxxx/
> Reported-by: Nathan Chancellor <nathan@xxxxxxxxxx>
> Closes: https://lore.kernel.org/lkml/20251121215819.GA1374726@ax162/
> Fixes: 3572e2edc7b6 ("locking/mutex: Redo __mutex_init()")
> Signed-off-by: Boqun Feng <boqun.feng@xxxxxxxxx>
> ---
>   kernel/locking/mutex-debug.c | 10 +---------
>   kernel/locking/mutex.c       |  8 +++++++-
>   kernel/locking/mutex.h       |  5 ++---
>   3 files changed, 10 insertions(+), 13 deletions(-)
>
> diff --git a/kernel/locking/mutex-debug.c b/kernel/locking/mutex-debug.c
> index 949103fd8e9b..2c6b02d4699b 100644
> --- a/kernel/locking/mutex-debug.c
> +++ b/kernel/locking/mutex-debug.c
> @@ -78,16 +78,8 @@ void debug_mutex_unlock(struct mutex *lock)
>   	}
>   }
>   
> -void debug_mutex_init(struct mutex *lock, const char *name,
> -		      struct lock_class_key *key)
> +void debug_mutex_init(struct mutex *lock)
>   {
> -#ifdef CONFIG_DEBUG_LOCK_ALLOC
> -	/*
> -	 * Make sure we are not reinitializing a held lock:
> -	 */
> -	debug_check_no_locks_freed((void *)lock, sizeof(*lock));
> -	lockdep_init_map_wait(&lock->dep_map, name, key, 0, LD_WAIT_SLEEP);
> -#endif
>   	lock->magic = lock;
>   }
>   
> diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
> index f3bb352a368d..2a1d165b3167 100644
> --- a/kernel/locking/mutex.c
> +++ b/kernel/locking/mutex.c
> @@ -51,6 +51,7 @@ static void __mutex_init_generic(struct mutex *lock)
>   #ifdef CONFIG_MUTEX_SPIN_ON_OWNER
>   	osq_lock_init(&lock->osq);
>   #endif
> +	debug_mutex_init(lock);
>   }
>   
>   static inline struct task_struct *__owner_task(unsigned long owner)
> @@ -173,7 +174,12 @@ static __always_inline bool __mutex_unlock_fast(struct mutex *lock)
>   void mutex_init_lockep(struct mutex *lock, const char *name, struct lock_class_key *key)
>   {
>   	__mutex_init_generic(lock);
> -	debug_mutex_init(lock, name, key);
> +
> +	/*
> +	 * Make sure we are not reinitializing a held lock:
> +	 */
> +	debug_check_no_locks_freed((void *)lock, sizeof(*lock));
> +	lockdep_init_map_wait(&lock->dep_map, name, key, 0, LD_WAIT_SLEEP);
>   }
>   EXPORT_SYMBOL(mutex_init_lockep);
>   #endif /* !CONFIG_DEBUG_LOCK_ALLOC */
> diff --git a/kernel/locking/mutex.h b/kernel/locking/mutex.h
> index 2e8080a9bee3..9ad4da8cea00 100644
> --- a/kernel/locking/mutex.h
> +++ b/kernel/locking/mutex.h
> @@ -59,8 +59,7 @@ extern void debug_mutex_add_waiter(struct mutex *lock,
>   extern void debug_mutex_remove_waiter(struct mutex *lock, struct mutex_waiter *waiter,
>   				      struct task_struct *task);
>   extern void debug_mutex_unlock(struct mutex *lock);
> -extern void debug_mutex_init(struct mutex *lock, const char *name,
> -			     struct lock_class_key *key);
> +extern void debug_mutex_init(struct mutex *lock);
>   #else /* CONFIG_DEBUG_MUTEXES */
>   # define debug_mutex_lock_common(lock, waiter)		do { } while (0)
>   # define debug_mutex_wake_waiter(lock, waiter)		do { } while (0)
> @@ -68,6 +67,6 @@ extern void debug_mutex_init(struct mutex *lock, const char *name,
>   # define debug_mutex_add_waiter(lock, waiter, ti)	do { } while (0)
>   # define debug_mutex_remove_waiter(lock, waiter, ti)	do { } while (0)
>   # define debug_mutex_unlock(lock)			do { } while (0)
> -# define debug_mutex_init(lock, name, key)		do { } while (0)
> +# define debug_mutex_init(lock)				do { } while (0)
>   #endif /* !CONFIG_DEBUG_MUTEXES */
>   #endif /* CONFIG_PREEMPT_RT */
Reviewed-by: Waiman Long <longman@xxxxxxxxxx>