netdev - Re: [PATCH net-next 05/15] idpf: add create vport and netdev configuration

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Message-ID: <CAF=yD-LUfyz9M4cKyE_eJUfWGzqtnVZDz4dH=PU2X1zz7N-9gA@mail.gmail.com>
Date: Wed, 7 Jun 2023 21:39:09 +0200
From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
To: Jakub Kicinski <kuba@...nel.org>
Cc: "Linga, Pavan Kumar" <pavan.kumar.linga@...el.com>, Tony Nguyen <anthony.l.nguyen@...el.com>, 
	davem@...emloft.net, pabeni@...hat.com, edumazet@...gle.com, 
	netdev@...r.kernel.org, emil.s.tantilov@...el.com, jesse.brandeburg@...el.com, 
	sridhar.samudrala@...el.com, shiraz.saleem@...el.com, sindhu.devale@...el.com, 
	willemb@...gle.com, decot@...gle.com, andrew@...n.ch, leon@...nel.org, 
	mst@...hat.com, simon.horman@...igine.com, shannon.nelson@....com, 
	stephen@...workplumber.org, Alan Brady <alan.brady@...el.com>, 
	Joshua Hay <joshua.a.hay@...el.com>, Madhu Chittim <madhu.chittim@...el.com>, 
	Phani Burra <phani.r.burra@...el.com>, 
	Shailendra Bhatnagar <shailendra.bhatnagar@...el.com>, 
	Krishneil Singh <krishneil.k.singh@...el.com>
Subject: Re: [PATCH net-next 05/15] idpf: add create vport and netdev configuration

On Wed, Jun 7, 2023 at 9:10 PM Jakub Kicinski <kuba@...nel.org> wrote:
>
> On Wed, 7 Jun 2023 20:20:57 +0200 Willem de Bruijn wrote:
> > > > Please use locks. Every single Intel driver comes with gazillion flags
> > > > and endless bugs when the flags go out of sync.
> > >
> > > Thanks for the feedback. Will use mutex lock instead of 'VC_MSG_PENDING'
> > > flag.
> >
> > Was that the intent of the comment?
> >
> > Or is it to replace these individual atomic test_and_set bit
> > operations with a single spinlock-protected critical section around
> > all the flag operations?
>
> No, no. Intel drivers have a history of adding flags to work around
> locking problems. Whatever this bit is protecting should be protected
> by a normal synchronization primitive instead.

Got it. Thanks for clarifying.

> I don't understand why.
>
> Replacing an atomic bitop with a spin lock is a non-change.