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authorNoralf Trønnes <noralf@tronnes.org>2019-05-06 20:01:30 +0200
committerNoralf Trønnes <noralf@tronnes.org>2019-05-14 16:11:28 +0200
commit03a9606e7feef902979bbc0601d6d93e764f251d (patch)
tree14c3cdd6a72146a03461da62b60d17a539d4ffb6 /Documentation/gpu/todo.rst
parent094aa54f0f9e9185babebf95745d71b07a84321c (diff)
downloadlinux-03a9606e7feef902979bbc0601d6d93e764f251d.tar.gz
drm/fb-helper: Avoid race with DRM userspace
drm_fb_helper_is_bound() is used to check if DRM userspace is in control.
This is done by looking at the fb on the primary plane. By the time
fb-helper gets around to committing, it's possible that the facts have
changed.

Avoid this race by holding the drm_device->master_mutex lock while
committing. When DRM userspace does its first open, it will now wait
until fb-helper is done. The helper will stay away if there's a master.

Two igt tests fail with the new 'bail out if master' rule. Work around
this by relaxing this rule for drm_fb_helper_restore_fbdev_mode_unlocked()
until the tests have been fixed. Add todo entry for this.

Locking rule: Always take the fb-helper lock first.

v5: drm_fb_helper_restore_fbdev_mode_unlocked(): Use
    restore_fbdev_mode_force()

v2:
- Remove drm_fb_helper_is_bound() (Daniel Vetter)
- No need to check fb_helper->dev->master in
  drm_fb_helper_single_fb_probe(), restore_fbdev_mode() has the check.

Suggested-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20190506180139.6913-3-noralf@tronnes.org
Diffstat (limited to 'Documentation/gpu/todo.rst')
-rw-r--r--Documentation/gpu/todo.rst8
1 files changed, 8 insertions, 0 deletions
diff --git a/Documentation/gpu/todo.rst b/Documentation/gpu/todo.rst
index 06ccff9165d5..66f05f4e469f 100644
--- a/Documentation/gpu/todo.rst
+++ b/Documentation/gpu/todo.rst
@@ -281,6 +281,14 @@ it to use drm_mode_hsync() instead.
 
 Contact: Sean Paul
 
+drm_fb_helper tasks
+-------------------
+
+- drm_fb_helper_restore_fbdev_mode_unlocked() should call restore_fbdev_mode()
+  not the _force variant so it can bail out if there is a master. But first
+  these igt tests need to be fixed: kms_fbcon_fbt@psr and
+  kms_fbcon_fbt@psr-suspend.
+
 Core refactorings
 =================