linux-kernel - Re: [net-next v6 5/9] net: napi: Add napi

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Message-ID: <Z03vkLXa-wajZZ8T@LQ3V64L9R2>
Date: Mon, 2 Dec 2024 09:34:08 -0800
From: Joe Damato <jdamato@...tly.com>
To: Jakub Kicinski <kuba@...nel.org>
Cc: Guenter Roeck <linux@...ck-us.net>, netdev@...r.kernel.org,
	mkarsten@...terloo.ca, skhawaja@...gle.com, sdf@...ichev.me,
	bjorn@...osinc.com, amritha.nambiar@...el.com,
	sridhar.samudrala@...el.com, willemdebruijn.kernel@...il.com,
	edumazet@...gle.com, "David S. Miller" <davem@...emloft.net>,
	Paolo Abeni <pabeni@...hat.com>, Jonathan Corbet <corbet@....net>,
	Jiri Pirko <jiri@...nulli.us>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Lorenzo Bianconi <lorenzo@...nel.org>,
	Johannes Berg <johannes.berg@...el.com>,
	"open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
	open list <linux-kernel@...r.kernel.org>, pcnet32@...ntier.com
Subject: Re: [net-next v6 5/9] net: napi: Add napi_config

On Sat, Nov 30, 2024 at 12:45:01PM -0800, Jakub Kicinski wrote:
> On Wed, 27 Nov 2024 12:00:02 -0800 Joe Damato wrote:
> > CPU 0:
> > pcnet32_open
> >    lock(lp->lock)
> >      napi_enable
> >        napi_hash_add <- before this executes, CPU 1 proceeds
> >          lock(napi_hash_lock)
> > CPU 1:
> >   pcnet32_close
> >     napi_disable
> >       napi_hash_del
> >         lock(napi_hash_lock)
> >          < INTERRUPT >
> 
> How about making napi_hash_lock irq-safe ?
> It's a control path lock, it should be fine to disable irqs.

Ah, right. That should fix it.

I'll write a fixes against net and change the napi_hash_lock to use
spin_lock_irqsave and spin_lock_irqrestore and send shortly.

> >             pcnet32_interrupt
> >               lock(lp->lock)
>