* Re: [PATCH] drm/fb-helper: Try to protect cleanup against delayed setup
2021-07-13 13:59 [PATCH] drm/fb-helper: Try to protect cleanup against delayed setup Daniel Vetter
@ 2021-07-13 20:21 ` Sam Ravnborg
2021-07-15 14:18 ` Thomas Zimmermann
2022-11-15 9:30 ` [Intel-gfx] " Andrzej Hajda
2 siblings, 0 replies; 5+ messages in thread
From: Sam Ravnborg @ 2021-07-13 20:21 UTC (permalink / raw)
To: Daniel Vetter
Cc: David Airlie, Intel Graphics Development, DRI Development,
Chris Wilson, Thomas Zimmermann, Daniel Vetter
Hi Daniel,
On Tue, Jul 13, 2021 at 03:59:22PM +0200, Daniel Vetter wrote:
> 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
s/doen't/doesn't/
> + * 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
s/doen't/doesn't/
> + * 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);
I could not find any better spot to clear deferred_setup - so I think
this is OK.
With the two spellign issues fixed:
Acked-by: Sam Ravnborg <sam@ravnborg.org>
No r-b as I an not too fluent in these code paths and all the locking.
Sam
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH] drm/fb-helper: Try to protect cleanup against delayed setup
2021-07-13 13:59 [PATCH] drm/fb-helper: Try to protect cleanup against delayed setup Daniel Vetter
2021-07-13 20:21 ` Sam Ravnborg
@ 2021-07-15 14:18 ` Thomas Zimmermann
2022-11-15 9:30 ` [Intel-gfx] " Andrzej Hajda
2 siblings, 0 replies; 5+ messages in thread
From: Thomas Zimmermann @ 2021-07-15 14:18 UTC (permalink / raw)
To: Daniel Vetter, DRI Development
Cc: David Airlie, Daniel Vetter, Intel Graphics Development,
Chris Wilson
[-- Attachment #1.1: Type: text/plain, Size: 3016 bytes --]
Am 13.07.21 um 15:59 schrieb 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>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
> ---
> 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);
>
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Felix Imendörffer
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^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [Intel-gfx] [PATCH] drm/fb-helper: Try to protect cleanup against delayed setup
2021-07-13 13:59 [PATCH] drm/fb-helper: Try to protect cleanup against delayed setup Daniel Vetter
2021-07-13 20:21 ` Sam Ravnborg
2021-07-15 14:18 ` Thomas Zimmermann
@ 2022-11-15 9:30 ` Andrzej Hajda
2022-11-16 9:31 ` Daniel Vetter
2 siblings, 1 reply; 5+ messages in thread
From: Andrzej Hajda @ 2022-11-15 9:30 UTC (permalink / raw)
To: Daniel Vetter, DRI Development
Cc: David Airlie, Intel Graphics Development, Chris Wilson,
Thomas Zimmermann, Daniel Vetter
On 13.07.2021 15:59, Daniel Vetter wrote:
> 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>
Reviewed-by: Andrzej Hajda <andrzej.hajda@intel.com>
Regards
Andrzej
> ---
> 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);
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [Intel-gfx] [PATCH] drm/fb-helper: Try to protect cleanup against delayed setup
2022-11-15 9:30 ` [Intel-gfx] " Andrzej Hajda
@ 2022-11-16 9:31 ` Daniel Vetter
0 siblings, 0 replies; 5+ messages in thread
From: Daniel Vetter @ 2022-11-16 9:31 UTC (permalink / raw)
To: Andrzej Hajda
Cc: David Airlie, Daniel Vetter, Intel Graphics Development,
Chris Wilson, DRI Development, Thomas Zimmermann, Daniel Vetter
On Tue, Nov 15, 2022 at 10:30:01AM +0100, Andrzej Hajda wrote:
> On 13.07.2021 15:59, Daniel Vetter wrote:
> > 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>
>
> Reviewed-by: Andrzej Hajda <andrzej.hajda@intel.com>
I just dropped this one from my patch pile a while ago, because there were
conflicts. If you like it, feel free to resurrect&rebase and then merge it
(but maybe cc intel-gfx so the CI there can test it).
-Daniel
>
> Regards
> Andrzej
>
> > ---
> > 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);
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
^ permalink raw reply [flat|nested] 5+ messages in thread