Re: [PATCH 3/6] locking/local_lock: Introduce local_lock_is_locked().

[Sebastian Andrzej Siewior <bigeasy@linutronix.de>]

On 2025-04-30 20:27:15 [-0700], Alexei Starovoitov wrote:
> --- a/include/linux/local_lock_internal.h
> +++ b/include/linux/local_lock_internal.h
> @@ -285,4 +288,9 @@ do {								\
>  		__local_trylock(lock);				\
>  	})
>  
> +/* migration must be disabled before calling __local_lock_is_locked */
> +#include "../../kernel/locking/rtmutex_common.h"
> +#define __local_lock_is_locked(__lock)					\
> +	(rt_mutex_owner(&this_cpu_ptr(__lock)->lock) == current)

So I've been looking if we really need rt_mutex_owner() or if
rt_mutex_base_is_locked() could do the job. Judging from the slub-free
case, the rt_mutex_base_is_locked() would be just fine. The alloc case
on the other hand probably not so much. On the other hand since we don't
accept allocations from hardirq or NMI the "caller == owner" case should
never be observed. Unless buggy & debugging and this should then also be
observed by lockdep. Right?

If there is another case where recursion can be observed and need to be
addressed I would prefer to move the function (+define) to
include/linux/rtmutex.h. instead of doing this "../../ include".

>  #endif /* CONFIG_PREEMPT_RT */

Sebastian