netdev - Re: [PATCH v3 net] net: solve a NAPI race

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Date:   Mon, 27 Feb 2017 15:23:15 -0800
From:   Stephen Hemminger <stephen@...workplumber.org>
To:     David Miller <davem@...emloft.net>
Cc:     eric.dumazet@...il.com, netdev@...r.kernel.org
Subject: Re: [PATCH v3 net] net: solve a NAPI race

On Mon, 27 Feb 2017 17:48:54 -0500 (EST)
David Miller <davem@...emloft.net> wrote:

> From: Stephen Hemminger <stephen@...workplumber.org>
> Date: Mon, 27 Feb 2017 14:44:55 -0800
> 
> > On Mon, 27 Feb 2017 14:35:17 -0800
> > Eric Dumazet <eric.dumazet@...il.com> wrote:
> >   
> >> On Mon, 2017-02-27 at 14:14 -0800, Stephen Hemminger wrote:
> >>   
> >> > The original design (as Davem mentioned) was that IRQ's must be disabled
> >> > during device polling. If that was true, then the race above
> >> > would be impossible.    
> >> 
> >> I would love to see an alternative patch.  
> > 
> > Turn off busy poll? 
> > The poll stuff runs risk of breaking more things.  
> 
> Eric is exactly trying to make busy poll even more prominent in
> the stack, not less prominent.
> 
> It's an important component of some performance improvements he is
> working on.

Maybe making IRQ controlled as part of the network device model
(instead of a side effect left to device driver to handle) would
be less problematic.

Really just shooting in the dark because I don't have any of the problematic
hardware to play with.