linux-kernel - Re: [PATCH] net: dsa: mv88e6060: Fix false positive lockdep splat

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Message-ID: <56289967.6010909@baylibre.com>
Date:	Thu, 22 Oct 2015 10:08:07 +0200
From:	Neil Armstrong <narmstrong@...libre.com>
To:	Andrew Lunn <andrew@...n.ch>
Cc:	"David S. Miller" <davem@...emloft.net>,
	Florian Fainelli <f.fainelli@...il.com>,
	Guenter Roeck <linux@...ck-us.net>,
	vivien.didelot@...oirfairelinux.com,
	Fabian Frederick <fabf@...net.be>,
	Pavel Nakonechny <pavel.nakonechny@...tlab.ru>,
	Joe Perches <joe@...ches.com>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, nbd@...nwrt.org,
	sergei.shtylyov@...entembedded.com
Subject: Re: [PATCH] net: dsa: mv88e6060: Fix false positive lockdep splat

On 10/21/2015 06:14 PM, Andrew Lunn wrote:
> On Wed, Oct 21, 2015 at 05:37:45PM +0200, Neil Armstrong wrote:
>> Like the change made for mv88e6xxx, use mutex_lock_nested() to avoid
>> lockdep to give false positives because of nested MDIO busses.
> 
> Hi Neil
> 
> We now have three instances of this, since mdio-mux.c has the same
> code. Maybe now would be a good time to refactor this code into
> mdiobus_read_nested() and mdiobus_write_nested() in mdio_bus.c?  At
> the same time, add BUG_ON(in_interrupt()) similar to the non-nested
> versions?
> 
> 	Andrew
> 
Well, mdio-mux also calls switch_fn inside the mdio_lock, clean refactoring
would introduce a separate lock and call the nested variants.
Is that ok ? Can someone test mdio-mux if I make the change ?


Neil
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