Re: [PATCH 0/1] [RFC] DRM locking issues during early open

[Andy Whitcroft <apw@canonical.com>]

On Fri, Apr 20, 2012 at 10:40:35AM +0100, Dave Airlie wrote:

> I've just revisited this, maybe I'm going insane but why does
> drm_global_mutex not stop this?
> 
> drm_get_pci_dev takes drm_global_mutex before calling drm_fill_in_dev
> and drm_get_minor.
> 
> Now the fops should be pointing at stub_open at this point, as we
> won't have switched to the per device fops yet,
> and one of the first things drm_stub_open does is take the
> drm_global_mutex before doing the idr lookup.
> 
> So is the problem opening some sysfs or proc file early?

I may be reading things wrong but the initialisation does indeed hold
drm_global_mutex, but and back when this first occured we would have
been using kernel_lock() which was at least partially reentrant right?

Anyhow, I will go back to the reporter and try and get a proper
reproduce by, there is no point in fixing something which is something
else.

-apw