netdev - Re: [PATCH net-next 1/3] net: provide macros for commonly copied lockless queue stop/wake code

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Message-ID: <5f1ea1ed-739d-4d0d-a08e-748249ef8175@paulmck-laptop>
Date:   Thu, 6 Apr 2023 09:25:10 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     Herbert Xu <herbert@...dor.apana.org.au>,
        Alexander Duyck <alexander.duyck@...il.com>,
        Heiner Kallweit <hkallweit1@...il.com>, davem@...emloft.net,
        netdev@...r.kernel.org, edumazet@...gle.com, pabeni@...hat.com
Subject: Re: [PATCH net-next 1/3] net: provide macros for commonly copied
 lockless queue stop/wake code

On Thu, Apr 06, 2023 at 08:56:29AM -0700, Jakub Kicinski wrote:
> On Thu, 6 Apr 2023 08:45:10 -0700 Paul E. McKenney wrote:
> > > Starting the queue only happens from softirq (I hope) and stopping 
> > > can happen from any context. So we're risking false-starts again.
> > > I think this puts to bed any hope of making this code safe against
> > > false-starts with just barriers :(  
> > 
> > Is it possible to jam all the relevant state into a single variable?
> > (I believe that that answer is "no", but just in case asking this question
> > inspires someone to come up with a good idea.)
> 
> Not in any obvious way, half of the state is driver-specific the other
> half is flags maintained by the core :S

Hey, I had to ask!  ;-)

							Thanx, Paul