netdev - Re: [PATCH 1/7] 8139cp: Improve accuracy of cp_interrupt() return, to survive IRQ storms

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Message-ID: <1443050290.74600.44.camel@infradead.org>
Date:	Thu, 24 Sep 2015 00:18:10 +0100
From:	David Woodhouse <dwmw2@...radead.org>
To:	Francois Romieu <romieu@...zoreil.com>
Cc:	David Miller <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH 1/7] 8139cp: Improve accuracy of cp_interrupt() return,
 to survive IRQ storms

On Thu, 2015-09-24 at 00:44 +0200, Francois Romieu wrote:
> David Woodhouse <dwmw2@...radead.org> :
> [...]
> > But sure, for now I'll drop this from the series and I can try to
> > convince you separately.
> 
> You may as well change the IRQ storm avoidance logic so that it does not
> require conformant driver code if you do not want to waste more time :o)

That's not entirely trivial — at a certain level we *do* require that
drivers don't lie to the core IRQ logic.

I suppose even if a rogue driver is returning IRQ_HANDLED in an IRQ
storm, when it's *not* actually doing anything or making any progress,
perhaps there's a way we could detect that we're always going straight
back into the next interrupt handler as *soon* as we exit the previous
one. Perhaps there's merit in exploring that option.

I'm not sure that gives you a valid excuse for not wanting to fix the
driver though :)

I might start by "clarifying" the documentation on the IRQ handler's
return value...

-- 
David Woodhouse                            Open Source Technology Centre
David.Woodhouse@...el.com                              Intel Corporation

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