Re: GRO + splice panics in 3.7.0-rc5

Hi Eric,

On Thu, Nov 15, 2012 at 03:49:04PM -0800, Eric Dumazet wrote:

On Thu, 2012-11-15 at 23:28 +0100, Willy Tarreau wrote:

quoted

Hello,

I was just about to make a quick comparison between LRO and GRO in
3.7.0-rc5 to see if LRO still had the big advantage I've always observed,
but I failed the test because as soon as I enable LRO + splice, the kernel
panics and reboots.

I could not yet manage to catch the panic output, I could just reliably
reproduce it, it crashes instantly.

All I can say at the moment is the following :
  - test consist in forwarding HTTP traffic between two NICs via haproxy
  - driver used was myri10ge
  - LRO + recv+send : OK
  - LRO + splice : OK
  - GRO + recv+send : OK
  - GRO + splice : panic
  - no such problem was observed in 3.6.6 so I think this is a recent
    regression.

I'll go back digging for more information, but as I'm used to often see
Eric suggest the right candidates for reverting, I wanted to report the
issue here in case there are easy ones to try first.

Hi Willy

Nothing particular comes to mind, there were a lot of recent changes
that could trigger this kind of bug.

OK, no problem.

A stack trace would be useful of course ;)

I'll arrange to get one, then to bisect. I'll also try to reproduce with
the onboard NIC (sky2) to see if this is something related to the driver
itself. I can't promise anything before the end of the week-end, though.

Thanks !
Willy