On Fri, Jan 20, 2023 at 06:58:20AM -0800, Arjan van de Ven wrote:
> On 1/20/2023 5:55 AM, Hernan Ponce de Leon wrote:
> > From: Hernan Ponce de Leon <hernanl.leon@xxxxxxxxxx>
> >
>
> > kernel/locking/rtmutex.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
> > index 010cf4e6d0b8..7ed9472edd48 100644
> > --- a/kernel/locking/rtmutex.c
> > +++ b/kernel/locking/rtmutex.c
> > @@ -235,7 +235,7 @@ static __always_inline void mark_rt_mutex_waiters(struct rt_mutex_base *lock)
> > unsigned long owner, *p = (unsigned long *) &lock->owner;
> > do {
> > - owner = *p;
> > + owner = READ_ONCE(*p);
> > } while (cmpxchg_relaxed(p, owner,
>
>
> I don't see how this makes any difference at all.
> *p can be read a dozen times and it's fine; cmpxchg has barrier semantics for compilers afaics
Doing so does suppress a KCSAN warning. You could also use data_race()
if it turns out that the volatile semantics would prevent a valuable
compiler optimization.
Thanx, Paul
