On Tuesday, September 08, 2015 12:40:08 PM Peter Zijlstra wrote:

On Mon, Sep 07, 2015 at 11:33:21PM +0200, Rafael J. Wysocki wrote:

quoted

On Monday, September 07, 2015 11:11:19 AM Jiang Liu wrote:
Peter, Ingo, some help from lockdep expert is needed.

We have a splat that almost certainly is a false positive (the original report
is here http://marc.info/?l=linux-kernel&m=144109156901959&w=4) and no ideas
how to make it go away.  Can you please have a look and advise?

I can't even find the relevant code :/

From that email I get kernfs_fop_write() which calls
kernfs_get_active(), but that does _NOT_ call cpu_up(), so that
callchain is shite.

The actual lockdep splat is also not really helpful, and is spraying
names over: acpi, device, sysfs and kernfs (do we really need that many
layeres of obfuscation for a simple file?)

So, please, start by explaining the thing proper such that simple people
like me know what to look for.

OK, I'll try to get that later this week.

Or maybe Jiang Liu can beat me to doing that. :-)

Thanks,
Rafael