From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joe Perches Subject: Re: [PATCH] drivers/staging/batman-adv: Use (pr|netdev)_ macro helpers Date: Tue, 15 Jun 2010 15:58:17 -0700 Message-ID: <1276642697.1586.151.camel@Joe-Laptop.home> References: <1275498615.23599.12.camel@Joe-Laptop.home> <1275509466.23599.43.camel@Joe-Laptop.home> <201006160023.04296.sven.eckelmann@gmx.de> <201006160037.48573.sven.eckelmann@gmx.de> Reply-To: The list for a Better Approach To Mobile Ad-hoc Networking Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: devel , Greg Kroah-Hartman , b.a.t.m.a.n-ZwoEplunGu2X36UT3dwlltHuzzzSOjJt@public.gmane.org, b.a.t.m.a.n-ZwoEplunGu2X36UT3dwllkB+6BGkLq7r@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Simon Wunderlich , Marek Lindner To: Sven Eckelmann , netdev Return-path: In-Reply-To: <201006160037.48573.sven.eckelmann-Mmb7MZpHnFY@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: b.a.t.m.a.n-bounces-ZwoEplunGu2X36UT3dwllkB+6BGkLq7r@public.gmane.org Errors-To: b.a.t.m.a.n-bounces-ZwoEplunGu2X36UT3dwllkB+6BGkLq7r@public.gmane.org List-Id: netdev.vger.kernel.org On Wed, 2010-06-16 at 00:37 +0200, Sven Eckelmann wrote: > Sven Eckelmann wrote: Hi Sven. > > The problem seems to be that dev_printk is used by netdev_printk (which is > > used by netdev_info). netdev_printk will add (netdev)->dev.parent as second > > parameter of dev_printk (and parent is NULL in our case). This macro will > > now call dev_driver_string with NULL as parameter and just dereference > > this null pointer. > > > > Maybe it is related to something else, but at least I think that this could > > be the cause of the crash. Nope, I think that's exactly correct. > As far as I understand, the netdev_* stuff is made to be used by real drivers > with more or less physical hardware. batman-adv is a virtual bridge used for > mesh networks. Like net/bridge/ it has no physical parent device and only > other net_devices are used inside of it - which may have real physical network > devices as parents. > Please correct me if my assumption is wrong. No correction necessary... netdev_printk and netdev_ are meant to be used with parented network devices. I think that netdev_ will eventually do the right thing when dev->dev.parent is NULL. Right now, that'd be a bit of an expensive test as it would be expanded in place for every use of the macro. Right now it's: #define netdev_printk(level, netdev, format, args...) \ dev_printk(level, (netdev)->dev.parent, \ "%s: " format, \ netdev_name(netdev), ##args) It could be something like: #define netdev_printk(level, netdev, format, args...) \ do { \ if ((netdev)->dev.parent) \ dev_printk(level, (netdev)->dev.parent, \ "%s: " format, \ netdev_name(netdev), ##args); \ else \ printk(level "%s: " format, \ netdev_name(netdev), ##args); \ } while (0) Unfortunately, that just about doubles the format string space, so I don't really want to do that. If/when %pV is accepted, http://lkml.org/lkml/2010/3/4/17 http://lkml.org/lkml/2010/3/4/18 then the netdev_ macros will be converted to functions, so size reduced with an added test for dev.parent == NULL without the need to double the string space.