Drivers are allowed (actually have to) disable unrelated crtcs in
their ->set_config callback (when we steal all the connectors from
that crtc). If they do that they'll clear crtc->fb to NULL.
Which results in a refcount leak, since the drm core is keeping track
of that reference.
To fix this track the old fb of all crtcs and adjust references for
all of them. Of course, since we only hold an additional reference for
the fb for the current crtc we need to increase refcounts before we
drop the old one.
This approach has the benefit that it inches us a bit closer to an
atomic modeset world, where we want to update the config of all crtcs
in one step.
This regression has been introduce in the framebuffer refcount
conversion, specifically in
commit b0d1232589
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date: Tue Dec 11 01:07:12 2012 +0100
drm: refcounting for crtc framebuffers
Reported-by: Russell King <linux@arm.linux.org.uk>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: stable@vger.kernel.org
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Dave Airlie <airlied@redhat.com>
************************************************************
* For the very latest on DRI development, please see: *
* http://dri.freedesktop.org/ *
************************************************************
The Direct Rendering Manager (drm) is a device-independent kernel-level
device driver that provides support for the XFree86 Direct Rendering
Infrastructure (DRI).
The DRM supports the Direct Rendering Infrastructure (DRI) in four major
ways:
1. The DRM provides synchronized access to the graphics hardware via
the use of an optimized two-tiered lock.
2. The DRM enforces the DRI security policy for access to the graphics
hardware by only allowing authenticated X11 clients access to
restricted regions of memory.
3. The DRM provides a generic DMA engine, complete with multiple
queues and the ability to detect the need for an OpenGL context
switch.
4. The DRM is extensible via the use of small device-specific modules
that rely extensively on the API exported by the DRM module.
Documentation on the DRI is available from:
http://dri.freedesktop.org/wiki/Documentation
http://sourceforge.net/project/showfiles.php?group_id=387
http://dri.sourceforge.net/doc/
For specific information about kernel-level support, see:
The Direct Rendering Manager, Kernel Support for the Direct Rendering
Infrastructure
http://dri.sourceforge.net/doc/drm_low_level.html
Hardware Locking for the Direct Rendering Infrastructure
http://dri.sourceforge.net/doc/hardware_locking_low_level.html
A Security Analysis of the Direct Rendering Infrastructure
http://dri.sourceforge.net/doc/security_low_level.html
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