Re: [Patch net-next v2] mlx5: use RCU lock in mlx5_eq_cq_get()

[Eric Dumazet]

On 02/06/2019 04:04 PM, Cong Wang wrote:

> synchronize_irq() is called before mlx5_cq_put(), so I don't
> see why readers could get 0 refcnt.

Then the more reasons to get rid of the refcount increment/decrement completely 
...

Technically, even the rcu_read_lock() and rcu_read_unlock() are not needed,
since synchronize_irq() is enough.

> 
> For the rds you mentioned, it doesn't wait for readers, this
> is why it needs to check against 0 and why it is different from
> this one.
> 
> Thanks.
>