Re: [PATCH v3 06/14] locking/mutex: Expose mutex_owner()

John Stultz
2023-04-25T14:54:04Z

On Sat, Apr 22, 2023 at 11:36 AM Peter Zijlstra <peterz@infradead.org> wrote:
>
> On Tue, Apr 11, 2023 at 04:25:03AM +0000, John Stultz wrote:
>
> > include/linux/mutex.h | 2 ++
> > kernel/locking/mutex.c | 5 +++++
> > 2 files changed, 7 insertions(+)
> >
> > diff --git a/include/linux/mutex.h b/include/linux/mutex.h
> > index 8f226d460f51..ebdc59cb0bf6 100644
> > --- a/include/linux/mutex.h
> > +++ b/include/linux/mutex.h
> > @@ -118,6 +118,8 @@ do { \
> > extern void __mutex_init(struct mutex *lock, const char *name,
> > struct lock_class_key *key);
> >
> > +extern struct task_struct *mutex_owner(struct mutex *lock);
> > +
> > /**
> > * mutex_is_locked - is the mutex locked
> > * @lock: the mutex to be queried
> > diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
> > index 45f1b7519f63..cbc34d5f4486 100644
> > --- a/kernel/locking/mutex.c
> > +++ b/kernel/locking/mutex.c
> > @@ -81,6 +81,11 @@ static inline struct task_struct *__mutex_owner(struct mutex *lock)
> > return (struct task_struct *)(atomic_long_read(&lock->owner) & ~MUTEX_FLAGS);
> > }
> >
> > +struct task_struct *mutex_owner(struct mutex *lock)
> > +{
> > + return __mutex_owner(lock);
> > +}
> > +
> > static inline struct task_struct *__owner_task(unsigned long owner)
> > {
> > return (struct task_struct *)(owner & ~MUTEX_FLAGS);
>
>
> Urgh, no.
>
> It exposes mutex_owner() far wider than it should be, and also it turns
> what should be a simple load into a function call :/
>
> Looking at the lastest patches I have here this used to be an inline in
> kernel/locking/mutex.h and kernel/sched/core.c got to #include
> "../locking/mutex.h".

Sure. I'll rework it this way.

Thanks again for the feedback, and apologies for any frustration caused.
-john