[Bug 46711] Monitor not turning on after DisplayPort re-plug in Xorg

https://bugs.freedesktop.org/show_bug.cgi?id=46711

--- Comment #7 from Alex Deucher agd5f@yahoo.com 2012-04-16 08:25:12 PDT --- (In reply to comment #6)

How to investigate this potential conflict with userspace?

Because, as I originally wrote, without X running monitor comes back fine.

It's probably missing locking in the radeon kernel modesetting code. The ddx registers an event handler in the xserver and then the desktop environment does something with the event. See drmmode_uevent_init() and drmmode_handle_uevents() in drmmode_display.c in xf86-video-ati.