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SubjectRe: drm_vm.c:drm_mmap: possible circular locking dependency detected
On Sun, Jan 03, 2010 at 03:14:18AM -0800, Eric W. Biederman wrote:
> ebiederm@xmission.com (Eric W. Biederman) writes:
>
> > What to do about it is another question. It has just recently come to my
> > attention that we have more events like this
>
> In the specific case of serio what gets us in trouble is
> the call to sysfs_remove_group.
>
> If instead of independent calls to sysfs_create_group/sysfs_remove_group,
> you could move the groups into a list on dev->groups than we could solve
> two problems.
>
> - Userspace would see all of the attributes when the hotplug event is
> fired remove races.
>
> - We would not hold serio->drv_mutex over sysfs_remove_group so there
> would not be a possible deadlock on device removal.
>
> Does that change sound possible?

No, because attributes in question belong to driver+device combo. The
device will not go away when driver is unbound but we do want to remove
attributes.

--
Dmitry


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