linux-kernel - Re: [PATCH v2 net] net: phy: clear phydev->devlink when the link is deleted

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Message-ID: <808b7ab5-dc30-483b-81cc-397f14683963@quicinc.com>
Date: Thu, 5 Jun 2025 17:52:31 -0700
From: "Abhishek Chauhan (ABC)" <quic_abchauha@...cinc.com>
To: Wei Fang <wei.fang@....com>, Russell King <linux@...linux.org.uk>
CC: Florian Fainelli <f.fainelli@...il.com>,
        "andrew@...n.ch"
	<andrew@...n.ch>,
        "hkallweit1@...il.com" <hkallweit1@...il.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "edumazet@...gle.com"
	<edumazet@...gle.com>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "pabeni@...hat.com" <pabeni@...hat.com>,
        "xiaolei.wang@...driver.com"
	<xiaolei.wang@...driver.com>,
        "netdev@...r.kernel.org"
	<netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>,
        "imx@...ts.linux.dev" <imx@...ts.linux.dev>,
        Sarosh Hasan <quic_sarohasa@...cinc.com>
Subject: Re: [PATCH v2 net] net: phy: clear phydev->devlink when the link is
 deleted



On 6/4/2025 5:08 AM, Wei Fang wrote:
>> On Wed, Jun 04, 2025 at 06:00:54AM +0000, Wei Fang wrote:
>>> I think this issue is also introduced by the commit bc66fa87d4fd
>>> ("net: phy: Add link between phy dev and mac dev"). I suggested
>>> to change the DL_FLAG_STATELESS flag to
>>> DL_FLAG_AUTOREMOVE_SUPPLIER to solve this issue, so that
>>> the consumer (MAC controller) driver will be automatically removed
>>> when the link is removed. The changes are as follows.
>>
>> I suspect this still has problems. This is fine if the PHY device is
>> going away and as you say device_del() is called.
>>
>> However, you need to consider the case where a MAC driver attaches the
>> PHY during .ndo_open and releases it during .ndo_release. These will
>> happen multiple times.
> 
> .ndo_release? Do you mean .ndo_stop?
> 
>>
>> Each time the MAC driver attaches to the PHY via .ndo_open, we will
>> call device_link_add(), but the device link will not be removed when
>> .ndo_release is called.
>>
>> Either device_link_add() will fail, or we will eat memory each time
>> the device is closed and re-opened.
> 
> Below is what I find in the kernel doc of device_link_add().
> https://elixir.bootlin.com/linux/v6.15/source/drivers/base/core.c#L711
> 
> if a device link between the given @consumer and @supplier pair
> exists already when this function is called for them, the existing link will
> be returned regardless of its current type and status.
> 
> Therefore, it will not create new link each time the netdev is re-opened.
> 
@Wei, 

We were able to verify the suggestion what you gave us. 
No crash is seen now. 
Should we raise a patch or shall we wait until this is clarified and 
Russell has no more further questions. ? 

I am okay with anything. 

>>
>> If that is correct, then we're trading one problem for another.
>>
>