linux-kernel - Re: [PATCH net-next v21 3/5] net: Add the possibility to support a selected hwtstamp in netdevice

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Message-ID: <3fe00f86-60f3-42a2-9491-7b876531c215@tuxon.dev>
Date: Fri, 17 Jan 2025 14:19:15 +0200
From: Claudiu Beznea <claudiu.beznea@...on.dev>
To: Kory Maincent <kory.maincent@...tlin.com>
Cc: Florian Fainelli <florian.fainelli@...adcom.com>,
 Broadcom internal kernel review list
 <bcm-kernel-feedback-list@...adcom.com>, Andrew Lunn <andrew@...n.ch>,
 Heiner Kallweit <hkallweit1@...il.com>, Russell King
 <linux@...linux.org.uk>, "David S. Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>, Richard Cochran <richardcochran@...il.com>,
 Radu Pirea <radu-nicolae.pirea@....nxp.com>,
 Jay Vosburgh <j.vosburgh@...il.com>, Andy Gospodarek <andy@...yhouse.net>,
 Nicolas Ferre <nicolas.ferre@...rochip.com>,
 Willem de Bruijn <willemdebruijn.kernel@...il.com>,
 Jonathan Corbet <corbet@....net>,
 Horatiu Vultur <horatiu.vultur@...rochip.com>, UNGLinuxDriver@...rochip.com,
 Simon Horman <horms@...nel.org>, Vladimir Oltean <vladimir.oltean@....com>,
 donald.hunter@...il.com, danieller@...dia.com, ecree.xilinx@...il.com,
 Andrew Lunn <andrew+netdev@...n.ch>,
 Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
 linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
 linux-doc@...r.kernel.org, Maxime Chevallier
 <maxime.chevallier@...tlin.com>, Rahul Rameshbabu <rrameshbabu@...dia.com>,
 Willem de Bruijn <willemb@...gle.com>,
 Shannon Nelson <shannon.nelson@....com>,
 Alexandra Winter <wintera@...ux.ibm.com>
Subject: Re: [PATCH net-next v21 3/5] net: Add the possibility to support a
 selected hwtstamp in netdevice

On 17.01.2025 14:06, Kory Maincent wrote:
> On Fri, 17 Jan 2025 13:57:41 +0200
> Claudiu Beznea <claudiu.beznea@...on.dev> wrote:
> 
>> Hi, Kory,
>>
>> On 12.12.2024 19:06, Kory Maincent wrote:
>>> Introduce the description of a hwtstamp provider, mainly defined with a
>>> the hwtstamp source and the phydev pointer.
>>>
>>> Add a hwtstamp provider description within the netdev structure to
>>> allow saving the hwtstamp we want to use. This prepares for future
>>> support of an ethtool netlink command to select the desired hwtstamp
>>> provider. By default, the old API that does not support hwtstamp
>>> selectability is used, meaning the hwtstamp provider pointer is unset.
>>>
>>> Signed-off-by: Kory Maincent <kory.maincent@...tlin.com>  
>>
>> I'm getting this error when doing suspend/resume on the Renesas RZ/G3S
>> Smarc Module + RZ SMARC Carrier II board:
>>
>> [   39.032969] =============================
>> [   39.032983] WARNING: suspicious RCU usage
>> [   39.033000] 6.13.0-rc7-next-20250116-arm64-renesas-00002-g35245dfdc62c
>> #7 Not tainted
>> [   39.033019] -----------------------------
>> [   39.033033] drivers/net/phy/phy_device.c:2004 suspicious
>> rcu_dereference_protected() usage!
> 
> Thanks for the report.
> Oh so it seems there are cases where phy_detach is not called under RTNL lock!
> 
> This should solve the issue:
> -               hwprov = rtnl_dereference(dev->hwprov);
> +               rcu_read_lock()
> +               hwprov = rcu_dereference(dev->hwprov);
>                 /* Disable timestamp if it is the one selected */
>                 if (hwprov && hwprov->phydev == phydev) {
>                         rcu_assign_pointer(dev->hwprov, NULL);
>                         kfree_rcu(hwprov, rcu_head);
>                 }
> +               rcu_read_unlock();

Just tested. The issue is gone. You can add my:

Tested-by: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>

Thank you,
Claudiu

> 
> I will send a patch soon.
> 
> Regards,