drm/i915: Don't grab crtc mutexes in intel_modeset_gem_init()

This change “drm/i915: Don't grab crtc mutexes in intel_modeset_gem_init()” (commit 7ad228b) in Linux kernel is authored by Ville Syrjälä <ville.syrjala [at] linux.intel.com> on Tue Jan 7 16:15:36 2014 +0200.

Description of "drm/i915: Don't grab crtc mutexes in intel_modeset_gem_init()"

The change “drm/i915: Don't grab crtc mutexes in intel_modeset_gem_init()” introduces changes as follows.

drm/i915: Don't grab crtc mutexes in intel_modeset_gem_init()

When the pipe A force quirk is applied the code will attempt to grab
a crtc mutex during intel_modeset_setup_hw_state(). If we're already
holding all crtc mutexes this will obviously deadlock every time.

So instead of using drm_modeset_lock_all() just grab the
mode_config.mutex. This is enough to avoid the unlocked mutex warnings
from certain lower level functions.

The regression was introduced in:

 commit 027476642811f8559cbe00ef6cc54db230e48a20
 Author: Ville Syrjälä <ville.syrjala@linux.intel.com>
 Date:   Mon Dec 2 11:08:06 2013 +0200

    drm/i915: Take modeset locks around intel_modeset_setup_hw_state()

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: stable@vger.kernel.org
[danvet: Add cc: stable since the offending commit has that, too.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

Linux kernel releases containing commit 7ad228b

The Linux kernel releases containing this commit are as follows.

Linux kernel code changes from "drm/i915: Don't grab crtc mutexes in intel_modeset_gem_init()"

There are 4 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.

 drivers/gpu/drm/i915/intel_display.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
 
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 769b864465a9..2bde35d34eb9 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -11053,10 +11053,10 @@ void intel_modeset_gem_init(struct drm_device *dev)
 
 	intel_setup_overlay(dev);
 
-	drm_modeset_lock_all(dev);
+	mutex_lock(&dev->mode_config.mutex);
 	drm_mode_config_reset(dev);
 	intel_modeset_setup_hw_state(dev, false);
-	drm_modeset_unlock_all(dev);
+	mutex_unlock(&dev->mode_config.mutex);
 }
 
 void intel_modeset_cleanup(struct drm_device *dev)

The commit for this change in Linux stable tree is 7ad228b (patch).

Last modified: 2020/02/10