Re: [PATCH] Fix data race in mark_rt_mutex_waiters

[Hernan Ponce de Leon]

On 1/24/2023 5:04 PM, Waiman Long wrote:
> On 1/24/23 10:52, Peter Zijlstra wrote:
> > On Tue, Jan 24, 2023 at 10:42:24AM -0500, Waiman Long wrote:
> >
> > > I would suggest to do it as suggested by PeterZ. Instead of set_bit(),
> > > however, it is probably better to use atomic_long_or() like
> > >
> > > atomic_long_or_relaxed(RT_MUTEX_HAS_WAITERS, (atomic_long_t 
> > > *)&lock->owner)
> > That function doesn't exist, atomic_long_or() is implicitly relaxed for
> > not returning a value.
> You are right. atomic_long_or() doesn't have variants like some others.
>
> Cheers,
> Longman

When you say "replace the whole of that function", do you mean "barrier 
included"? I argue in the other email that I think this should not 
affect correctness (at least not obviously), but removing the barrier is 
doing more than just fixing the data race as this patch suggests.

Hernan