Re: Latest net-next from GIT panic

On Wed, Sep 20, 2017 at 10:55 AM, Paweł Staszewski
[off-list ref] wrote:

W dniu 2017-09-20 o 19:50, Cong Wang pisze:

On Wed, Sep 20, 2017 at 6:11 AM, Eric Dumazet [off-list ref]
wrote:

Sorry for top-posting, but this is to give context to Wei, since Pawel
used a top posting way to report his bisection.

Wei, can you take a look at Pawel report ?

Crash happens in dst_destroy() at following :

if (dst->dev)
     dev_put(dst->dev); <<CRASH>>


dst->dev is not NULL, but netdev->pcpu_refcnt is NULL

65 ff 08                decl   %gs:(%rax)   // CRASH since rax = NULL



Pawel, please share your netdevices and routing setup  ?

Looks like a double dev_put() on some dev...

Pawel, do you have any idea how this is triggered? Does your
test try to remove some network device? If so which one?
I noticed you have at least multiple vlan, bond and ixgbe
devices.

Just after i start bgp sessions
So when host is starting i have all bgp sessions to upstreams shutdown

To trigger panic i just enable all 6x bgp sessions at once to upstreams -
and zebra is start to pull prefixes and push them to the kernel

Then some traffic is generated from test hosts thru this backup router and
panic is generated - every time after 10 to 15 seconds after bgp sessions
are connected.

I'm not removing any interface at this time or do anything with interfaces -
just wait.

And yes there are vlans attached to the bond devices
but dmesg at this time shows nothing about interfaces or flaps.

This is very odd.

We only free netdevice in free_netdev() and it is only called when
we unregister a netdevice. Otherwise pcpu_refcnt is impossible
to be NULL.