On 16-11-18 03:21 PM, Eric Dumazet wrote:
> On Fri, 2016-11-18 at 11:00 -0800, John Fastabend wrote:
>
>
>> static void free_receive_bufs(struct virtnet_info *vi)
>> {
>> + struct bpf_prog *old_prog;
>> int i;
>>
>> for (i = 0; i < vi->max_queue_pairs; i++) {
>> while (vi->rq[i].pages)
>> __free_pages(get_a_page(&vi->rq[i], GFP_KERNEL), 0);
>> +
>> + old_prog = rcu_dereference(vi->rq[i].xdp_prog);
>
> Seems wrong to me.
>
Yep it is wrong should be rtnl_dereference() here and the
rcu_dereference() calls earlier in the patch need to be _bh().
> Are you sure lockdep (with CONFIG_PROVE_RCU=y) was happy with this ?
oops you are right it was missing.
>
>> + RCU_INIT_POINTER(vi->rq[i].xdp_prog, NULL);
>> + if (old_prog)
>> + bpf_prog_put(old_prog);
bpf_prog_put() waits a grace period of ref count is zero. That said on
driver unload we need to protect the bpf_prog_put with RTNL_LOCK() as
well.
I'll send out a v2 in a bit.
Thanks a lot.
>> }
>> }
>>
>>
>
>
