drm/i915: Hold mode_config lock whilst changing mode for lastclose()

commit c291be9dba370ba696a0d482249a212cf5c15f45 upstream.

Upon lastclose(), we switch back to the fbcon configuration. This
requires taking the mode_config lock in order to serialise the change
with output probing elsewhere.

Reported-by: Oleksij Rempel <bug-track@fisher-privat.net>
References: https://bugs.freedesktop.org/show_bug.cgi?id=48652
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Acked-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-Off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/gpu/drm/i915/intel_fb.c b/drivers/gpu/drm/i915/intel_fb.c
index 12a04b962b95f5a86bcd4aca83152ddb6f60efc4..2dea5aade996709af4b830799c4590e9797b2a72 100644 (file)
--- a/drivers/gpu/drm/i915/intel_fb.c
+++ b/drivers/gpu/drm/i915/intel_fb.c
@@ -283,6 +283,8 @@ void intel_fb_restore_mode(struct drm_device *dev)
        struct drm_mode_config *config = &dev->mode_config;
        struct drm_plane *plane;
 
+       mutex_lock(&dev->mode_config.mutex);
+
        ret = drm_fb_helper_restore_fbdev_mode(&dev_priv->fbdev->helper);
        if (ret)
                DRM_DEBUG("failed to restore crtc mode\n");
@@ -290,4 +292,6 @@ void intel_fb_restore_mode(struct drm_device *dev)
        /* Be sure to shut off any planes that may be active */
        list_for_each_entry(plane, &config->plane_list, head)
                plane->funcs->disable_plane(plane);
+
+       mutex_unlock(&dev->mode_config.mutex);
 }