netdev - Re: [PATCH net-next] docs: networking: document NAPI

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Message-ID: <20230315183649.7f42b1f0@hermes.local>
Date:   Wed, 15 Mar 2023 18:36:49 -0700
From:   Stephen Hemminger <stephen@...workplumber.org>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     davem@...emloft.net, netdev@...r.kernel.org, edumazet@...gle.com,
        pabeni@...hat.com, jesse.brandeburg@...el.com,
        anthony.l.nguyen@...el.com, corbet@....net,
        linux-doc@...r.kernel.org
Subject: Re: [PATCH net-next] docs: networking: document NAPI

On Wed, 15 Mar 2023 16:11:42 -0700
Jakub Kicinski <kuba@...nel.org> wrote:

> > 
> > The one thing missing, is how to handle level vs edge triggered interrupts.
> > For level triggered interrupts, the re-enable is inherently not racy.
> > I.e re-enabling interrupt when packet is present will cause an interrupt.
> > But for devices with edge triggered interrupts, it is often necessary to
> > poll and manually schedule again. Older documentation referred to this
> > as the "rotten packet" problem.
> > 
> > Maybe this is no longer a problem for drivers?
> > Or maybe all new hardware uses PCI MSI and is level triggered?  
> 
> It's still a problem depending on the exact design of the interrupt
> controller in the chip / tradeoffs the SW wants to make.
> I haven't actually read the LF doc, because I wasn't sure about the
> licenses (sigh)

I wrote the old NAPI from some older info that was available back then.