netdev - Re: [RFC net-next 04/10] devlink: always check if the devlink instance is registered

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Message-ID: <20221219135541.6e0a7cfd@kernel.org>
Date:   Mon, 19 Dec 2022 13:55:41 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Jacob Keller <jacob.e.keller@...el.com>
Cc:     <jiri@...nulli.us>, <leon@...nel.org>, <netdev@...r.kernel.org>
Subject: Re: [RFC net-next 04/10] devlink: always check if the devlink
 instance is registered

On Mon, 19 Dec 2022 09:48:54 -0800 Jacob Keller wrote:
> On 12/16/2022 5:19 PM, Jakub Kicinski wrote:
> > Always check under the instance lock whether the devlink instance
> > is still / already registered.
> 
> Ok. So now the reference ensures less about whats valid. It guarantees a
> lock but doesn't ensure that the devlink remains registered unless you
> acquire the lock and check that the devlink is alive under lock now?

Correct.

> > This is a no-op for the most part, as the unregistration path currently
> > waits for all references. On the init path, however, we may temporarily
> > open up a race with netdev code, if netdevs are registered before the
> > devlink instance. This is temporary, the next change fixes it, and this
> > commit has been split out for the ease of review.
> >   
> 
> This means you're adding the problem here, but its fixed in next commit..?

Yes, I can squash when posting for applying, but TBH I think the clarity
of the changes outweighs the tiny and transient race.