The existing net/net_dev_xmit trace event provides little information
about the skb that has been passed to the driver, and it is not
simple to add more since the skb may already have been freed at
the point the event is emitted.
Add a separate trace event before the skb is passed to the driver,
including most fields that are likely to be interesting for debugging
driver datapath behaviour.
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Because there is a possibility that skb is kfree_skb()ed and zero cleared
after ndo_start_xmit, we should not see the contents of skb like skb->len and
skb->dev->name after ndo_start_xmit. But trace_net_dev_xmit does that
and causes panic by NULL pointer dereference.
This patch fixes trace_net_dev_xmit not to see the contents of skb directly.
If you want to reproduce this panic,
1. Get tracepoint of net_dev_xmit on
2. Create 2 guests on KVM
2. Make 2 guests use virtio_net
4. Execute netperf from one to another for a long time as a network burden
5. host will panic(It takes about 30 minutes)
Signed-off-by: Koki Sanagi <sanagi.koki@jp.fujitsu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
