linux-kernel - Re: [PATCH] locking/mutex: Redo __mutex

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Message-ID: <10899bd0-09ca-4fcf-8142-3d5cd6e4fedf@redhat.com>
Date: Wed, 5 Nov 2025 08:49:05 -0500
From: Waiman Long <llong@...hat.com>
To: Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
 Waiman Long <llong@...hat.com>
Cc: linux-kernel@...r.kernel.org, Boqun Feng <boqun.feng@...il.com>,
 Ingo Molnar <mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org>,
 Will Deacon <will@...nel.org>
Subject: Re: [PATCH] locking/mutex: Redo __mutex_init()

On 11/5/25 2:57 AM, Sebastian Andrzej Siewior wrote:
> On 2025-11-04 11:21:27 [-0500], Waiman Long wrote:
>>> +#ifdef CONFIG_DEBUG_LOCK_ALLOC
>>> +void mutex_init_ld(struct mutex *lock, const char *name, struct lock_class_key *key);
>>> +
>>> +static inline void __mutex_init(struct mutex *lock, const char *name,
>>> +				struct lock_class_key *key)
>>> +{
>>> +	mutex_init_ld(lock, name, key);
>>> +}
>>> +#else
>>> +extern void mutex_init_plain(struct mutex *lock);
>>> +
>>> +static inline void __mutex_init(struct mutex *lock, const char *name,
>>> +				struct lock_class_key *key)
>>> +{
>>> +	mutex_init_plain(lock);
>>> +}
>>> +#endif /* !CONFIG_DEBUG_LOCK_ALLOC */
>> I think it is a good idea to eliminate useless strings in non-lockdep
>> kernel. However, the function names are kind of awkward to me. First of all,
>> it is hard to associate "ld" with lockdep as ld is also the name of the GNU
>> linker. I would prefer to fully spell out as "lockdep". The "_plain" suffix
>> also looks odd to me. How about using the original __mutex_init for the
>> plain version and __mutex_init_lockdep as the lockdep version which calls
>> __mutex_init and use similar naming scheme for the RT versions. What do you
>> think?
> What about
> 	mutex_init_plain() -> mutex_init_generic()
> 	mutex_init_ld() -> mutex_init_lockdep()
Yes, generic is a much better name.
>
> Using __mutex_init() for the basic/ generic init could work but we have
> already users 13 users (drivers/ mm/ net/) and the rust bindings are
> also attached to it. I would prefer the generic/ lockdep suffix.
>
> If you want __mutex_init() for the generic, regardless, we would first
> need to make room and then something like mutex_init_lockdep() could be
> the public interface replacing __mutex_init() in its current function.

Ah, I don't realize that there are users of __mutex_init() outside of 
the locking subsystem. In this case, we have to maintain the semantics 
of __mutex_init() to avoid affecting other subsystems.

Thanks for the clarification.

Cheers,
Longman