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Message-ID: <c3b05efb-e691-4947-84f9-cf524e7d2cd9@paulmck-laptop> Date: Thu, 6 Apr 2023 08:45:10 -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 07:46:48AM -0700, Jakub Kicinski wrote: > On Thu, 6 Apr 2023 07:17:09 -0700 Paul E. McKenney wrote: > > > > Mightn't preemption or interrupts cause further issues? Or are preemption > > > > and/or interrupts disabled across the relevant sections of code? > > > > > > The code in question is supposed to run in softirq context. So > > > both interrupts and preemption should be disabled. > > > > Agreed, preemption will be enabled in softirq, but interrupts can still > > happen, correct? > > 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.) Thanx, Paul
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