Re: rtmutex grabbed twice by same context in network code

[Darcy Watkins <dwatkins@tranzeo.com>]

On Mon, 2011-11-14 at 15:12 -0800, Thomas Gleixner wrote:
> On Mon, 14 Nov 2011, Darcy Watkins wrote:
> 
> > Hi,
> >
> > Anyone have insight into the kernel crash below?
> 
> Can you please enable CONFIG_PROVE_LOCKING ? That should tell us all
> the details.

Hi Thomas,

I tried that but couldn't fit the resulting system into the memory on
the device.  oops!   But I think I determined the cause.

The function header comments for netif_receive_skb() mentions it should
only be used under softirqd context.  I guess earlier kernel versions I
used didn't really care.  But the newest ones do.

To invoke it under the thread context, I used the technique described
in...

http://kerneltrap.org/mailarchive/linux-netdev/2010/5/19/6277601

...and it seems to avoid the crash.  Essentially the trick is to suspend
bottom half, then invoke netif_receive_skb(), then allow it.

When I looked at dev.c in netif_rx_ni() I notice functions like
migate_disable/enable(), are those related to SMP support?


Thanks,

Darcy
> 
> Thanks,
> 
>         tglx
> 
>