BUG: circular locking dependency detected

[Dave Airlie]

On Thu, Jan 31, 2013 at 9:52 AM, Linus Torvalds
<torvalds at linux-foundation.org> wrote:
> On Thu, Jan 31, 2013 at 9:19 AM, Russell King <rmk at arm.linux.org.uk> wrote:
>>
>> So... what you seem to be telling me is that 3.9 is going to be a
>> release which issues lockdep complaints when the console blanks, and
>> you think that's acceptable?
>>
>> Adding Linus and Andrew so they're aware of this issue...
>
> Oh, we're extremely aware of it. And it's not a new issue, the locking
> problem have apparently been around forever, although I'm not sure why
> the lockdep splat itself started happening only recently.
>
> They'll make it into 3.9, it's 3.8 that won't have them. The patches
> initially caused way *worse* behavior than just a lockdep splat - they
> caused actual hard lockups (and that was *after* the initial series of
> fixes). That got fixed (hopefully for the last case!) fairly recently,
> and I'm not willing to take the scary patch-series that has had
> several problem cases.

Well we didn't have any lock validation support before Daniel added it
a couple of kernels back,
so instead of hidden locking problems we've had from time began, we now have
lockdep detectable locking problems.

Dave.