On Wed, Sep 19, 2018 at 01:19:10PM +0800, jianchao.wang wrote: > Hi Ming > > On 09/18/2018 06:19 PM, Ming Lei wrote: > > + unsigned long __percpu *percpu_count; > > + > > + WARN_ON_ONCE(__ref_is_percpu(ref, &percpu_count)); > > + > > + /* get one extra ref for avoiding race with .release */ > > + rcu_read_lock_sched(); > > + atomic_long_add(1, &ref->count); > > + rcu_read_unlock_sched(); > > + } > > The rcu_read_lock_sched here is redundant. We have been in the critical section > of a spin_lock_irqsave. Right. > > The atomic_long_add(1, &ref->count) may have two result. > 1. ref->count > 1 > it will not drop to zero any more. > 2. ref->count == 1 > it has dropped to zero and .release may be running. IMO, both the two cases are fine and supported, or do you have other concern about this way? thanks, Ming
