Currently when allocating a framebuffer fails, the gem object gets
unrefed at the bottom of the call stack in __intel_framebuffer_create,
not where it gets refed, which is in intel_framebuffer_create_for_mode
(via i915_gem_alloc_object) and in intel_user_framebuffer_create
(via drm_gem_object_lookup).
This invites mistakes: __intel_framebuffer_create is also called from
intelfb_alloc, and as discovered by Tvrtko Ursulin, a double unref
was introduced there with a8bb681827 ("drm/i915: Fix error path leak
in fbdev fb allocation").
As suggested by Ville Syrjälä, fix the double unref and improve code
clarity by moving the unref away from __intel_framebuffer_create to
where the gem object gets refed.
Based on Tvrtko Ursulin's original v2.
v3: On fb alloc failure, unref gem object where it gets refed,
fix double unref in separate commit (Ville Syrjälä)
v4: Lock struct_mutex on unref (Chris Wilson)
v5: Rebase on drm-intel-nightly 2015y-09m-01d-09h-06m-08s UTC,
rephrase commit message (Jani Nicula)
Tested-by: Pierre Moreau <pierre.morrow@free.fr>
[MBP 5,3 2009 nvidia MCP79 + G96 pre-retina]
Tested-by: Paul Hordiienko <pvt.gord@gmail.com>
[MBP 6,2 2010 intel ILK + nvidia GT216 pre-retina]
Tested-by: William Brown <william@blackhats.net.au>
[MBP 8,2 2011 intel SNB + amd turks pre-retina]
Tested-by: Lukas Wunner <lukas@wunner.de>
[MBP 9,1 2012 intel IVB + nvidia GK107 pre-retina]
Tested-by: Bruno Bierbaumer <bruno@bierbaumer.net>
[MBP 11,3 2013 intel HSW + nvidia GK107 retina]
Fixes: a8bb681827 ("drm/i915: Fix error path leak in fbdev fb
allocation")
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/2161c5062ef5d6458f8ae14d924a26d4d1dba317.1446892879.git.lukas@wunner.de
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
dcb1394e74