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

[Dmitry Torokhov]

On Sun, Jan 03, 2010 at 03:14:18AM -0800, Eric W. Biederman wrote:
> ebiederm@xxxxxxxxxxxx (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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