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

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Message-ID: <20241031093628.faiupqqny7oco7uz@DEN-DL-M70577>
Date: Thu, 31 Oct 2024 09:36:28 +0000
From: Daniel Machon <daniel.machon@...rochip.com>
To: Jakub Kicinski <kuba@...nel.org>
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, 24 Oct 2024 00:01:29 +0200 Daniel Machon wrote:
> > +             spin_lock_irqsave(&port->tx_skbs.lock, flags);
> > +             skb_queue_walk_safe(&port->tx_skbs, skb, skb_tmp) {
> > +                     if (SPARX5_SKB_CB(skb)->ts_id != id)
> > +                             continue;
> > +
> > +                     __skb_unlink(skb, &port->tx_skbs);
> > +                     skb_match = skb;
> > +                     break;
> > +             }
> > +             spin_unlock_irqrestore(&port->tx_skbs.lock, flags);
> 
> 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?

[1] 3a70e0d4c9d7 ("net: lan966x: Fix possible deadlock inside PTP")

/Daniel