Re: [PATCH net-next] tuntap: introduce tx skb ring

Eric Dumazet
2016-05-16T03:56:43Z

On Mon, 2016-05-16 at 09:17 +0800, Jason Wang wrote:
> We used to queue tx packets in sk_receive_queue, this is less
> efficient since it requires spinlocks to synchronize between producer
> and consumer.

...

> struct tun_struct *detached;
> + /* reader lock */
> + spinlock_t rlock;
> + unsigned long tail;
> + struct tun_desc tx_descs[TUN_RING_SIZE];
> + /* writer lock */
> + spinlock_t wlock;
> + unsigned long head;
> };
>

Ok, we had these kind of ideas floating around for many other cases,
like qdisc, UDP or af_packet sockets...

I believe we should have a common set of helpers, not hidden in
drivers/net/tun.c but in net/core/skb_ring.c or something, with more
flexibility (like the number of slots)

BTW, why are you using spin_lock_irqsave() in tun_net_xmit() and
tun_peek() ?

BH should be disabled already (in tun_next_xmit()), and we can not
transmit from hard irq.

Thanks.