netdev - Re: [PATCH v3 0/9] Phy, mdiobus, and netdev struct device fixes

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Message-Id: <20150924.155137.1429397912516096627.davem@davemloft.net>
Date:	Thu, 24 Sep 2015 15:51:37 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	andrew@...n.ch
Cc:	linux@....linux.org.uk, f.fainelli@...il.com,
	thomas.petazzoni@...e-electrons.com, devicetree@...r.kernel.org,
	sgoutham@...ium.com, rric@...nel.org, frowand.list@...il.com,
	linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
	robh+dt@...nel.org, michal.simek@...inx.com,
	netdev@...r.kernel.org, soren.brinkmann@...inx.com,
	isubramanian@....com, grant.likely@...aro.org, leoli@...escale.com,
	kchudgar@....com, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3 0/9] Phy, mdiobus, and netdev struct device fixes

From: Andrew Lunn <andrew@...n.ch>
Date: Fri, 25 Sep 2015 00:26:54 +0200

> On Thu, Sep 24, 2015 at 03:15:54PM -0700, David Miller wrote:
>> From: Andrew Lunn <andrew@...n.ch>
>> Date: Thu, 24 Sep 2015 23:57:31 +0200
>> 
>> > I built the FEC driver as a module, and it won't unload:
>> > 
>> >  kernel:unregister_netdevice: waiting for eth1 to become free. Usage count = 1
>> > unregister_netdevice: waiting for eth1 to become free. Usage count = 1
>> > 
>> > i assume because DSA holds a reference. I've not tried a fully module
>> > build, DSA has issues with that.
>> > 
>> > Tested-by: Andrew Lunn <andrew@...n.ch>
>> 
>> So, is this a regression?
> 
> Sorry, worded that badly. Since DSA is still active, it should not be
> possible to unload the FEC driver. DSA should have a reference to it,
> and mdio-mux also should have a reference to the mdio bus of the FEC
> driver.
> 
> As Russell requested, i will re-test without his patches, just to make
> sure.

Something needs to hold into the underlying device refcount of a DSA
blob so that an unload can't even be attempted in that state.
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