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Date: Mon, 03 Jun 2013 16:59:56 +0300
From: Eliezer Tamir <eliezer.tamir@linux.intel.com>
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To: Eric Dumazet <eric.dumazet@gmail.com>
CC: David Miller <davem@davemloft.net>, linux-kernel@vger.kernel.org,
        netdev@vger.kernel.org, Jesse Brandeburg <jesse.brandeburg@intel.com>,
        Don Skidmore <donald.c.skidmore@intel.com>,
        e1000-devel@lists.sourceforge.net,
        Willem de Bruijn <willemb@google.com>,
        Ben Hutchings <bhutchings@solarflare.com>,
        Andi Kleen <andi@firstfloor.org>, HPA <hpa@zytor.com>,
        Eilon Greenstien <eilong@broadcom.com>,
        Or Gerlitz <or.gerlitz@gmail.com>, Alex Rosenbaum <alexr@mellanox.com>,
        Eliezer Tamir <eliezer@tamir.org.il>
Subject: Re: [PATCH v8 net-next 5/7] net: simple poll/select low latency socket
 poll
References: <20130603080107.18273.34279.stgit@ladj378.jer.intel.com>  <20130603080200.18273.52073.stgit@ladj378.jer.intel.com> <1370265324.24311.136.camel@edumazet-glaptop>
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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.

-Eliezer