Re: drm_vm.c:drm_mmap: possible circular locking dependency detected

[Eric W. Biederman]

Tejun Heo <tj@xxxxxxxxxx> writes:

> It's interesting that the above cases arn't common drivers.  AFAICS,
> the problem cases would usually be cases like above where the user is
> a rather complex software entity or drivers which implement some form
> of self detaching via sysfs.  For the former group, I agree that
> splitting deleting and draining (or simply skipping the draining part
> or active reference counting both of which basically achieve the same
> thing) would be an easy way out as it would be generally easy to leave
> the data structures dangling till the references go away.
>
> How about simply introducing an interface to mark sysfs nodes which
> don't require active reference counting and using them on those nodes?

That might work.  However it does not seem to address the case of
bond_sysfs, especially with someone doing rmmod bonding.

I think the brainstorm is on the right track.  I think we just need to look
at a few more cases in depth so that we can see a pattern and generalize
what can be done.

Eric
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