Hi,
a deadlock was introduced by commit 60a5ca015ffd2aacfe5674b5a401cd2a37159e07
Author: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
Date: Fri Jun 13 11:10:53 2014 +0300
drm/i915: Add locking around framebuffer_references--
The commit amended intel_display.c:intel_user_framebuffer_destroy() with
mutex_lock(&dev->struct_mutex).
A few weeks prior Chris Wilson had amended intel_fbdev.c:intelfb_create()
with a call to drm_framebuffer_unreference() while &dev->struct_mutex is
locked (commit edd586fe705e819bc711b5ed7194a0b6f9f1a7e1, "drm/i915: Discard
BIOS framebuffers too small to accommodate chosen mode").
This leads to the following call chain while &dev->struct_mutex is locked:
intel_fbdev.c:intelfb_create()
-> drm_crtc.c:drm_framebuffer_unreference()
-> drm_crtc.c:drm_framebuffer_free()
-> intel_display.c:intel_user_framebuffer_destroy()
The last function in that call chain attempts to re-lock the mutex.
The functionality added by Chris Wilson is thus rendered broken.
Best regards,
Lukas
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