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* [PATCH] drm/fb-helper: Try to protect cleanup against delayed setup
@ 2021-07-13 13:59 ` Daniel Vetter
  0 siblings, 0 replies; 13+ messages in thread
From: Daniel Vetter @ 2021-07-13 13:59 UTC (permalink / raw)
  To: DRI Development
  Cc: David Airlie, Daniel Vetter, Intel Graphics Development,
	Chris Wilson, Thomas Zimmermann, Daniel Vetter

Some vague evidences suggests this can go wrong. Try to prevent it by
holding the right mutex and clearing ->deferred_setup to make sure we
later on don't accidentally try to re-register the fbdev when the
driver thought it had it all cleaned up already.

v2: I realized that this is fundamentally butchered, and CI complained
about lockdep splats. So limit the critical section again and just add
a few notes what the proper fix is.

References: https://intel-gfx-ci.01.org/tree/linux-next/next-20201215/fi-byt-j1900/igt@i915_pm_rpm@module-reload.html
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
---
 drivers/gpu/drm/drm_fb_helper.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index 9d82fda274eb..8f11e5abb222 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -598,6 +598,9 @@ EXPORT_SYMBOL(drm_fb_helper_alloc_fbi);
  * A wrapper around unregister_framebuffer, to release the fb_info
  * framebuffer device. This must be called before releasing all resources for
  * @fb_helper by calling drm_fb_helper_fini().
+ *
+ * Note that this is fundamentally racy on hotunload because it doen't handle
+ * open fbdev file descriptors at all. Use drm_fbdev_generic_setup() instead.
  */
 void drm_fb_helper_unregister_fbi(struct drm_fb_helper *fb_helper)
 {
@@ -611,6 +614,9 @@ EXPORT_SYMBOL(drm_fb_helper_unregister_fbi);
  * @fb_helper: driver-allocated fbdev helper, can be NULL
  *
  * This cleans up all remaining resources associated with @fb_helper.
+ *
+ * Note that this is fundamentally racy on hotunload because it doen't handle
+ * open fbdev file descriptors at all. Use drm_fbdev_generic_setup() instead.
  */
 void drm_fb_helper_fini(struct drm_fb_helper *fb_helper)
 {
@@ -2382,6 +2388,10 @@ static void drm_fbdev_client_unregister(struct drm_client_dev *client)
 {
 	struct drm_fb_helper *fb_helper = drm_fb_helper_from_client(client);
 
+	mutex_lock(&fb_helper->lock);
+	fb_helper->deferred_setup = false;
+	mutex_unlock(&fb_helper->lock);
+
 	if (fb_helper->fbdev)
 		/* drm_fbdev_fb_destroy() takes care of cleanup */
 		drm_fb_helper_unregister_fbi(fb_helper);
-- 
2.32.0


^ permalink raw reply related	[flat|nested] 13+ messages in thread
end of thread, other threads:[~2022-11-16  9:31 UTC | newest]

Thread overview: 13+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-07-13 13:59 [PATCH] drm/fb-helper: Try to protect cleanup against delayed setup Daniel Vetter
2021-07-13 13:59 ` [Intel-gfx] " Daniel Vetter
2021-07-13 16:43 ` [Intel-gfx] ✗ Fi.CI.CHECKPATCH: warning for " Patchwork
2021-07-13 17:09 ` [Intel-gfx] ✓ Fi.CI.BAT: success " Patchwork
2021-07-13 20:21 ` [PATCH] " Sam Ravnborg
2021-07-13 20:21   ` [Intel-gfx] " Sam Ravnborg
2021-07-13 23:25 ` [Intel-gfx] ✗ Fi.CI.IGT: failure for " Patchwork
2021-07-15 14:18 ` [PATCH] " Thomas Zimmermann
2021-07-15 14:18   ` [Intel-gfx] " Thomas Zimmermann
2022-11-15  9:30 ` Andrzej Hajda
2022-11-15  9:30   ` Andrzej Hajda
2022-11-16  9:31   ` Daniel Vetter
2022-11-16  9:31     ` Daniel Vetter

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