Re: [RFC] net: napi fix

Andrew Gallatin
2007-12-13T14:20:15Z

Joonwoo Park wrote:
> 2007/12/13, Kok, Auke <auke-jan.h.kok@intel.com>:
>> David Miller wrote:
>>> From: Andrew Gallatin <gallatin@myri.com>
>>> Date: Wed, 12 Dec 2007 12:29:23 -0500
>>>
>>>> Is the netif_running() check even required?
>>> No, it is not.
>>>
>>> When a device is brought down, one of the first things
>>> that happens is that we wait for all pending NAPI polls
>>> to complete, then block any new polls from starting.
>> I think this was previously (pre-2.6.24) not the case, which is why
e1000 et al
>> has this check as well and that's exactly what is causing most of the
>> net_rx_action oopses in the first place. Without the netif_running()
check
>> previously the drivers were just unusable with NAPI and prone to
many races with
>> down (i.e. touching some ethtool ioctl which wants to do a reset
while routing
>> small packets at high numbers). that's why we added the
netif_running() check in
>> the first place :)
>>
>> There might be more drivers lurking that need this change...
>>
>> Auke
>>
>
> Also in my case, without netif_running() check, I cannot do ifconfig
down.
> It stucked if packet generator was sending packets.

If the netif_running() check is indeed required to make a device break
out of napi polling and respond to an ifconfig down, then I think the
netif_running() check should be moved up into net_rx_action() to avoid
potential for driver complexity and bugs like the ones you found.

Drew