On 2019/2/22 下午11:03, David Ahern wrote:
> On 2/21/19 11:14 PM, wenxu wrote:
>> build_state in the rcu_read_lock and disable the preempt
>>
>> rcu_read_lock();
>> ops = rcu_dereference(lwtun_encaps[encap_type]);
>> if (likely(ops && ops->build_state && try_module_get(ops->owner))) {
>> found = true;
>> ret = ops->build_state(encap, family, cfg, lws, extack);
>> if (ret)
>> module_put(ops->owner);
>> }
>> rcu_read_unlock();
>>
> Missed that.
>
> Once a reference is taken the rcu_read_lock can be dropped before
> calling build_state allowing the allocations to be GFP_KERNEL.
>
I don't think the rcu_read_lock can be dropped. The whole operation of the
reference should be protect
in the rcu_read_lock that ensure the ops will not be destroy (if it will be)
