Annoyance with msk(4) going up and down when initializing interface

[Edwin Groothuis]

On Mon, Jan 05, 2009 at 06:51:35PM +0900, Pyun YongHyeon wrote:
> On Fri, Jan 02, 2009 at 03:31:33PM -0800, Garrett Cooper wrote:
>  > Hi Pyun,
>  > 	I've noticed an issue for a while now with my chipset (I think that  
>  > this is post an MFC between 7.0 and 7.1, but I could be wrong).
>  > 	Basically, each CPU (with the ULE scheduler) grabs the task to check 
>  > for media status, goes out and attempts to get an IP, and if the  
>  > timing of the status modifications is just right, one of the CPU's  
>  > will mark the link up and others will mark it down, and it will stay  
>  > down.
> 
> No, the link state change event is protected by driver lock.
> 
>  > 	Same thing occurs when trying to get a DHCP request -- there will  
>  > typically be multiple requests and ACK's for any given requests.
>  > 	This occurs with my onboard NICs on my P5K-e motherboards on 7.1- 
>  > rc[12], and also 8-CURRENT.
> 
> If you're referring to multiple link UP/DOWN messages when
> dhclient(8) trying to get an IP address via DHCP it's normal for
> drivers that rely on mii(4) state change event. Technically it's
> not normal but it's the way how it was implemented on most drivers.
> Ideally drivers should not need to reset controllers when it's not
> absolutely required to reset hardwares but most drivers blindly
> reset hardware which in turn results in link renegotiation. You can
> see similiar behavour when alias addresseses are added to the
> interface. Because controllers that have complex firmware/embedded
> OS will take time to complete the reset operation, the reset
> operation would be pain to these controllers. Long time ago I added
> a hack to em(4) to mitigate the issue but I don't think it's way to
> go.
> NetBSD seems to have right fix in ioctl handler. However the
> approach will require careful checking of multicasting code of all
> drivers. I don't have all hardwares to test this and I don't know
> hardware internals of all drivers.

When booting diskless via PXE I sometimes run into this problem
too: machine boots via NFS, NIC gets down and up and oh, it doesn't
work anymore.

Edwin

-- 
Edwin Groothuis		Website: http://www.mavetju.org/
edwin at mavetju.org	Weblog:  http://www.mavetju.org/weblog/