netdev - Re: [PATCH net-next v2 10/15] net: lan969x: add PTP handler function

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Message-ID: <20241031171613.565e6eb7@kernel.org>
Date: Thu, 31 Oct 2024 17:16:13 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Daniel Machon <daniel.machon@...rochip.com>
Cc: "David S. Miller" <davem@...emloft.net>, Eric Dumazet
 <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>, Andrew Lunn
 <andrew+netdev@...n.ch>, Lars Povlsen <lars.povlsen@...rochip.com>, "Steen
 Hegelund" <Steen.Hegelund@...rochip.com>, <horatiu.vultur@...rochip.com>,
 <jensemil.schulzostergaard@...rochip.com>,
 <Parthiban.Veerasooran@...rochip.com>, <Raju.Lakkaraju@...rochip.com>,
 <UNGLinuxDriver@...rochip.com>, Richard Cochran <richardcochran@...il.com>,
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>, <jacob.e.keller@...el.com>,
 <ast@...erby.net>, <maxime.chevallier@...tlin.com>, <horms@...nel.org>,
 <netdev@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>,
 <linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>
Subject: Re: [PATCH net-next v2 10/15] net: lan969x: add PTP handler
 function

On Thu, 31 Oct 2024 09:36:28 +0000 Daniel Machon wrote:
> > For a followup for both drivers -- you're mixing irqsave and bare
> > spin_lock() here. The _irqsave/_irqrestore is not necessary, let's
> > drop it.
> >   
> > > +             spin_lock(&sparx5->ptp_ts_id_lock);  
> 
> Hi Jakub,
> 
> I agree it seems wrong to mix these.
> 
> I just talked to Horatiu, and he mentioned posting a similar fix for the
> lan966x driver some time ago [1]. Only this fix added
> _irqsave/_irqrestore to the ptp_ts_id_lock - so basically the opposite
> of what you are suggesting. Why do you think that the
> _irqsave/_irqrestore is not necessary?

Oh, I thought this is a real IRQ handler, not a threaded one.
I haven't read the code to figure out whether ptp_ts_id_lock
needs to be IRQ-safe, but in other places you lock if _irqsave
so yes, let's irqsave here, too.