[PATCH v2 0/2] fbdev fixes (need review)

[Lukas Wunner <lukas@wunner.de>]

On Fri, Oct 30, 2015 at 07:23:45PM +0100, Daniel Vetter wrote:
> I don't think there's a leak here really. We always assign ifbdev->fb in
> intelfb_alloc, which means the fbdev teardown code will take care of it.
> The correct approach is probably to not unref anything at all, or if we
> unref then we have to clear ifbdev->fb (since it's the reference that very
> pointer is holding that we're clearing up).

Oh, right, and ifbdev->helper.fb would have to be set to NULL as well.

However it turns out the fbdev teardown code can't cope with an fbdev
that's only partially initialized, it lacks proper null pointer checks.
Patch 1 in this series fixes that.

Patch 2 is another attempt at handling failure of intelfb_create():
On failure, ifbdev->helper.fbdev will be released by intelfb_create()
but the intel_framebuffer and the gem_object are NOT unrefed. To make
up for this, intel_fbdev_initial_config() will call intel_fbdev_fini(),
which not only unrefs the intel_framebuffer and the gem_object but also
frees the ifbdev. It's as if CONFIG_DRM_FBDEV_EMULATION wasn't set.

Not sure if this is the right way to go but seems more sensible to me
than keeping an fbdev around that's only halfway initialized. We've
kicked out the VGA console at this point but failed to initialize an
fbdev, the console will thus be unusable. If X11 manages to start up
without errors, it will at least be able to use the memory that would
otherwise be hogged by the unusable fbdev.

Note that if you find patch 2 acceptable, the modifications in patch 1
to the following functions would actually become optional since they
already check if ifbdev is a null pointer (let me know if you want these
dropped): intel_fbdev_set_suspend(), intel_fbdev_output_poll_changed(),
intel_fbdev_restore_mode().

The patches are also browsable on GitHub:
https://github.com/l1k/linux/commits/intel_fbdev_fixes

Best regards,

Lukas


Lukas Wunner (2):
  drm/i915: Fix oops caused by fbdev initialization failure
  drm/i915: Tear down fbdev if initialization fails

 drivers/gpu/drm/i915/i915_debugfs.c | 24 +++++++++++++-----------
 drivers/gpu/drm/i915/i915_dma.c     |  1 +
 drivers/gpu/drm/i915/intel_dp_mst.c | 10 ++++++++--
 drivers/gpu/drm/i915/intel_fbdev.c  | 25 +++++++++++++++----------
 4 files changed, 37 insertions(+), 23 deletions(-)

-- 
1.8.5.2 (Apple Git-48)

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