Re: [PATCH v8 net-next 5/7] net: simple poll/select low latency socket poll

[Eliezer Tamir <eliezer.tamir@linux.intel.com>]

On 03/06/2013 16:59, Eliezer Tamir wrote:
> On 03/06/2013 16:15, Eric Dumazet wrote:
>> On Mon, 2013-06-03 at 11:02 +0300, Eliezer Tamir wrote:
>>>       sock = file->private_data;
>>> -    return sock->ops->poll(file, sock, wait);
>>> +
>>> +    poll_result = sock->ops->poll(file, sock, wait);
>>> +
>>> +    if (!(poll_result & (POLLRDNORM | POLLERR | POLLRDHUP |
>>> POLLHUP)) &&
>>> +        sk_valid_ll(sock->sk) && sk_poll_ll(sock->sk, 1))
>>> +            poll_result = sock->ops->poll(file, sock, NULL);
>>> +
>>> +    return poll_result;
>>>   }
>>>
>>>   static int sock_mmap(struct file *file, struct vm_area_struct *vma)
>>>
>>
>>
>> In fact, for TCP, POLLOUT event being ready can also be triggered by
>> incoming messages, as the ACK might allow the user application to push
>> more data in the write queue.
>>
>> And you might check wait->_key to avoid testing flags that user is not
>> interested into.
>
> yes, comparing to _key is more correct.
> In any case this needs to be completely rewritten for support for
> working well with a large number of sockets.
>

Is it possible for wait to be NULL? (do we need to check for that?)
I see that poll_does_not_wait() checks for that, but I could not find
anywhere this is actually done.

-Eliezer