Re: [PATCH v2] locking/rtmutex: Annotate API and implementation

[Bart Van Assche]

On 5/5/26 6:12 PM, Sebastian Andrzej Siewior wrote:
> On 2026-05-05 04:26:44 [+0200], Bart Van Assche wrote:
> > +context_lock_struct(rt_mutex);
>
> What does this do? Shouldn't this define the struct?

This enables context locking support for struct rt_mutex. I placed 
context_lock_struct() on a line by itself because in my opinion that
results in a header file that is easier to read compared to
context_lock_struct(name) { ... }.

> > --- a/kernel/locking/rtmutex_api.c
> > +++ b/kernel/locking/rtmutex_api.c
> > @@ -66,12 +67,14 @@ EXPORT_SYMBOL(rt_mutex_base_init);
> >    * @subclass: the lockdep subclass
> >    */
> >   void __sched rt_mutex_lock_nested(struct rt_mutex *lock, unsigned int subclass)
> > +	__no_context_analysis /* ignoring the return value below is fine in this case */
> >   {
> >   	__rt_mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, NULL, subclass);
> >   }
> >   EXPORT_SYMBOL_GPL(rt_mutex_lock_nested);
> >   
> >   void __sched _rt_mutex_lock_nest_lock(struct rt_mutex *lock, struct lockdep_map *nest_lock)
> > +	__no_context_analysis /* ignoring the return value below is fine in this case */
> >   {
> >   	__rt_mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, nest_lock, 0);
> >   }
>
> *Why* is it okay? Because the void always acquire the lock and only the
> conditional locking (which can be interrupted by signal/ timeout) return
> an error if they failed to acquire the lock.

Yes, that's correct.

> Something like that would be nice for the comment.
>
> Not sure if "__no_context_analysis" is the right thing to do here.
>    __acquires(lock) __no_context_analysis
>
> might be better if just __acquires leads to trouble.

There is an alternative that does not require __no_context_analysis:

void __sched rt_mutex_lock_nested(struct rt_mutex *lock, unsigned int 
subclass)
{
        int ret = __rt_mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, 
NULL, subclass);

        BUG_ON(ret);
}
EXPORT_SYMBOL_GPL(rt_mutex_lock_nested);

Please let me know which style you prefer.

Thanks,

Bart.