Re: tun: Use netif_receive_skb instead of netif_rx

Thomas Graf
2010-05-19T20:50:15Z

On Wed, 2010-05-19 at 14:00 -0400, Neil Horman wrote:
> I'm currently testing this, unfortunately, and its not breaking anything, but it
> doesn't allow cgroups to classify frames comming from tun interfaces. I'm still
> investigating, but I think the issue is that, because we call local_bh_disable
> with this patch, we wind up raising the count at SOFTIRQ_OFFSET in preempt_count
> for the task. Since the cgroup classifier has this check:
>
> if (softirq_count() != SOFTIRQ_OFFSET))
> return -1;
>
> We still fail to classify the frame. the cgroup classifier is assuming that any
> frame arriving with a softirq count of 1 means we came directly from the
> dev_queue_xmit routine and is safe to check current(). Any less than that, and
> something is wrong (as we at least need the local_bh_disable in dev_queue_xmit),
> and any more implies that we have nested calls to local_bh_disable, meaning
> we're really handling a softirq context.

It is a hack but the only method to check for softirq context I found. I
would favor using a flag if there was one.