On Thu, Jan 29, 2015 at 11:14:40PM -0800, Davidlohr Bueso wrote: > > +bool mutex_spin_on_owner(struct mutex *lock, struct task_struct *owner) > > { > > + bool ret; > > + > > rcu_read_lock(); > > - while (owner_running(lock, owner)) { > > - if (need_resched()) > > + while (true) { > > + /* Return success when the lock owner changed */ > > + if (lock->owner != owner) { > > Shouldn't this be a READ_ONCE(lock->owner)? We're in a loop and need to > avoid gcc giving us stale data if the owner is updated after a few > iterations, no?
There's a barrier() in that loop, and cpu_relax() also implies barrier(). I'm pretty sure that's more than sufficient to make GCC emit loads. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/