Re: [PATCH net V2] tuntap: synchronize through tfiles array instead of tun->numqueues

[Jason Wang]

On 2019/5/9 上午1:36, David Miller wrote:

From: Jason Wang <jasow...@redhat.com>
Date: Tue,  7 May 2019 00:03:36 -0400

@@ -1313,6 +1315,10 @@ static int tun_xdp_xmit(struct net_device *dev, int n,

tfile = rcu_dereference(tun->tfiles[smp_processor_id() %

                                            numqueues]);
+       if (!tfile) {
+               rcu_read_unlock();
+               return -ENXIO; /* Caller will free/return all frames */
+       }

spin_lock(&tfile->tx_ring.producer_lock);

        for (i = 0; i < n; i++) {

The only way we can see a NULL here is if a detach happened in parallel,
and if that happens we should retry the tfile[] indexing after resampling
numqueues rather than dropping the packet.

Ok, will fix this in V3.

Thanks