* Re: [PATCH] drivers/staging/batman-adv: Use (pr|netdev)_<level> macro helpers
[not found] ` <201006160037.48573.sven.eckelmann-Mmb7MZpHnFY@public.gmane.org>
@ 2010-06-15 22:58 ` Joe Perches
0 siblings, 0 replies; only message in thread
From: Joe Perches @ 2010-06-15 22:58 UTC (permalink / raw)
To: Sven Eckelmann, netdev
Cc: devel, Greg Kroah-Hartman,
b.a.t.m.a.n-ZwoEplunGu2X36UT3dwlltHuzzzSOjJt,
b.a.t.m.a.n-ZwoEplunGu2X36UT3dwllkB+6BGkLq7r,
linux-kernel-u79uwXL29TY76Z2rM5mHXA, Simon Wunderlich,
Marek Lindner
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_<level> are meant to be used
with parented network devices.
I think that netdev_<level> 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_<level> 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.
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