Re: [Intel-gfx] [PATCH v2] drm/i915/fbdev: Limit the global async-domain synchronization

[Chris Wilson]

On Thu, May 19, 2016 at 10:14:35PM +0200, Lukas Wunner wrote:
> Hi Chris,
> 
> On Thu, May 19, 2016 at 09:28:10AM +0100, Chris Wilson wrote:
> > During cleanup we have to synchronise with the async task we are using
> > to initialise and register our fbdev. Currently, we are using a full
> > synchronisation on the global domain, but we can restrict this to just
> > synchronising up to our task if we remember our cookie.
> > 
> > v2: async_synchronize_cookie() takes an exclusive upper bound, to
> > synchronize with our task we have to pass in the next cookie.
> 
> Oops, good catch, missed that in my own version of this patch:
> https://lists.freedesktop.org/archives/intel-gfx/2016-March/091257.html
> 
> > 
> > Signed-off-by: Chris Wilson 
> > ---
> >  drivers/gpu/drm/i915/intel_drv.h   |  1 +
> >  drivers/gpu/drm/i915/intel_fbdev.c | 31 ++-
> >  2 files changed, 19 insertions(+), 13 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/intel_drv.h 
> > b/drivers/gpu/drm/i915/intel_drv.h
> > index 3536292babe0..5bb045ba608e 100644
> > --- a/drivers/gpu/drm/i915/intel_drv.h
> > +++ b/drivers/gpu/drm/i915/intel_drv.h
> > @@ -159,6 +159,7 @@ struct intel_framebuffer {
> >  struct intel_fbdev {
> > struct drm_fb_helper helper;
> > struct intel_framebuffer *fb;
> > +   async_cookie_t cookie;
> > int preferred_bpp;
> >  };
> >  
> > diff --git a/drivers/gpu/drm/i915/intel_fbdev.c 
> > b/drivers/gpu/drm/i915/intel_fbdev.c
> > index 99e27530e264..2e9c3f38c023 100644
> > --- a/drivers/gpu/drm/i915/intel_fbdev.c
> > +++ b/drivers/gpu/drm/i915/intel_fbdev.c
> > @@ -538,8 +538,7 @@ static const struct drm_fb_helper_funcs 
> > intel_fb_helper_funcs = {
> > .fb_probe = intelfb_create,
> >  };
> >  
> > -static void intel_fbdev_destroy(struct drm_device *dev,
> > -   struct intel_fbdev *ifbdev)
> > +static void intel_fbdev_destroy(struct intel_fbdev *ifbdev)
> >  {
> > /* We rely on the object-free to release the VMA pinning for
> >  * the info->screen_base mmaping. Leaking the VMA is simpler than
> > @@ -554,12 +553,14 @@ static void intel_fbdev_destroy(struct drm_device 
> > *dev,
> > if (ifbdev->fb) {
> > drm_framebuffer_unregister_private(>fb->base);
> >  
> > -   mutex_lock(>struct_mutex);
> > +   mutex_lock(>helper.dev->struct_mutex);
> > intel_unpin_fb_obj(>fb->base, BIT(DRM_ROTATE_0));
> > -   mutex_unlock(>struct_mutex);
> > +   mutex_unlock(>helper.dev->struct_mutex);
> >  
> > drm_framebuffer_remove(>fb->base);
> > }
> > +
> > +   kfree(ifbdev);
> >  }
> >  
> >  /*
> > @@ -736,32 +737,36 @@ int intel_fbdev_init(struct drm_device *dev)
> >  
> >  static void intel_fbdev_initial_config(void *data, async_cookie_t cookie)
> >  {
> > -   struct drm_i915_private *dev_priv = data;
> > -   struct intel_fbdev *ifbdev = dev_priv->fbdev;
> > +   struct intel_fbdev *ifbdev = data;
> > +
> > +   ifbdev->cookie = 0;
> 
> Hm, why are you setting this to 0 here? IIUC the effect is that
> async_synchronize_cookie() will wait until intel_fbdev_initial_config()
> has been *entered*, but isn't the desired effect that it has *finished*?

True, it's also an unserialised write. Premature optimisation to not
block the teardown waiting for the out-of-order completion of earlier
tasks.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre
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Re: [Intel-gfx] [PATCH v2] drm/i915/fbdev: Limit the global async-domain synchronization

[Lukas Wunner]

Hi Chris,

On Thu, May 19, 2016 at 09:28:10AM +0100, Chris Wilson wrote:
> During cleanup we have to synchronise with the async task we are using
> to initialise and register our fbdev. Currently, we are using a full
> synchronisation on the global domain, but we can restrict this to just
> synchronising up to our task if we remember our cookie.
> 
> v2: async_synchronize_cookie() takes an exclusive upper bound, to
> synchronize with our task we have to pass in the next cookie.

Oops, good catch, missed that in my own version of this patch:
https://lists.freedesktop.org/archives/intel-gfx/2016-March/091257.html

> 
> Signed-off-by: Chris Wilson 
> ---
>  drivers/gpu/drm/i915/intel_drv.h   |  1 +
>  drivers/gpu/drm/i915/intel_fbdev.c | 31 ++-
>  2 files changed, 19 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_drv.h 
> b/drivers/gpu/drm/i915/intel_drv.h
> index 3536292babe0..5bb045ba608e 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -159,6 +159,7 @@ struct intel_framebuffer {
>  struct intel_fbdev {
>   struct drm_fb_helper helper;
>   struct intel_framebuffer *fb;
> + async_cookie_t cookie;
>   int preferred_bpp;
>  };
>  
> diff --git a/drivers/gpu/drm/i915/intel_fbdev.c 
> b/drivers/gpu/drm/i915/intel_fbdev.c
> index 99e27530e264..2e9c3f38c023 100644
> --- a/drivers/gpu/drm/i915/intel_fbdev.c
> +++ b/drivers/gpu/drm/i915/intel_fbdev.c
> @@ -538,8 +538,7 @@ static const struct drm_fb_helper_funcs 
> intel_fb_helper_funcs = {
>   .fb_probe = intelfb_create,
>  };
>  
> -static void intel_fbdev_destroy(struct drm_device *dev,
> - struct intel_fbdev *ifbdev)
> +static void intel_fbdev_destroy(struct intel_fbdev *ifbdev)
>  {
>   /* We rely on the object-free to release the VMA pinning for
>* the info->screen_base mmaping. Leaking the VMA is simpler than
> @@ -554,12 +553,14 @@ static void intel_fbdev_destroy(struct drm_device *dev,
>   if (ifbdev->fb) {
>   drm_framebuffer_unregister_private(>fb->base);
>  
> - mutex_lock(>struct_mutex);
> + mutex_lock(>helper.dev->struct_mutex);
>   intel_unpin_fb_obj(>fb->base, BIT(DRM_ROTATE_0));
> - mutex_unlock(>struct_mutex);
> + mutex_unlock(>helper.dev->struct_mutex);
>  
>   drm_framebuffer_remove(>fb->base);
>   }
> +
> + kfree(ifbdev);
>  }
>  
>  /*
> @@ -736,32 +737,36 @@ int intel_fbdev_init(struct drm_device *dev)
>  
>  static void intel_fbdev_initial_config(void *data, async_cookie_t cookie)
>  {
> - struct drm_i915_private *dev_priv = data;
> - struct intel_fbdev *ifbdev = dev_priv->fbdev;
> + struct intel_fbdev *ifbdev = data;
> +
> + ifbdev->cookie = 0;

Hm, why are you setting this to 0 here? IIUC the effect is that
async_synchronize_cookie() will wait until intel_fbdev_initial_config()
has been *entered*, but isn't the desired effect that it has *finished*?

Best regards,

Lukas

>  
>   /* Due to peculiar init order wrt to hpd handling this is separate. */
>   if (drm_fb_helper_initial_config(>helper,
>ifbdev->preferred_bpp))
> - intel_fbdev_fini(dev_priv->dev);
> + intel_fbdev_fini(ifbdev->helper.dev);
>  }
>  
>  void intel_fbdev_initial_config_async(struct drm_device *dev)
>  {
> - async_schedule(intel_fbdev_initial_config, to_i915(dev));
> + struct intel_fbdev *ifbdev = to_i915(dev)->fbdev;
> +
> + ifbdev->cookie = async_schedule(intel_fbdev_initial_config, ifbdev);
>  }
>  
>  void intel_fbdev_fini(struct drm_device *dev)
>  {
>   struct drm_i915_private *dev_priv = dev->dev_private;
> - if (!dev_priv->fbdev)
> + struct intel_fbdev *ifbdev = dev_priv->fbdev;
> +
> + if (!ifbdev)
>   return;
>  
>   flush_work(_priv->fbdev_suspend_work);
> + if (ifbdev->cookie && !current_is_async())
> + async_synchronize_cookie(ifbdev->cookie + 1);
>  
> - if (!current_is_async())
> - async_synchronize_full();
> - intel_fbdev_destroy(dev, dev_priv->fbdev);
> - kfree(dev_priv->fbdev);
> + intel_fbdev_destroy(ifbdev);
>   dev_priv->fbdev = NULL;
>  }
>  
> -- 
> 2.8.1
> 
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[Intel-gfx] [PATCH v2] drm/i915/fbdev: Limit the global async-domain synchronization

[Chris Wilson]

During cleanup we have to synchronise with the async task we are using
to initialise and register our fbdev. Currently, we are using a full
synchronisation on the global domain, but we can restrict this to just
synchronising up to our task if we remember our cookie.

v2: async_synchronize_cookie() takes an exclusive upper bound, to
synchronize with our task we have to pass in the next cookie.

Signed-off-by: Chris Wilson 
---
 drivers/gpu/drm/i915/intel_drv.h   |  1 +
 drivers/gpu/drm/i915/intel_fbdev.c | 31 ++-
 2 files changed, 19 insertions(+), 13 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 3536292babe0..5bb045ba608e 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -159,6 +159,7 @@ struct intel_framebuffer {
 struct intel_fbdev {
struct drm_fb_helper helper;
struct intel_framebuffer *fb;
+   async_cookie_t cookie;
int preferred_bpp;
 };
 
diff --git a/drivers/gpu/drm/i915/intel_fbdev.c 
b/drivers/gpu/drm/i915/intel_fbdev.c
index 99e27530e264..2e9c3f38c023 100644
--- a/drivers/gpu/drm/i915/intel_fbdev.c
+++ b/drivers/gpu/drm/i915/intel_fbdev.c
@@ -538,8 +538,7 @@ static const struct drm_fb_helper_funcs 
intel_fb_helper_funcs = {
.fb_probe = intelfb_create,
 };
 
-static void intel_fbdev_destroy(struct drm_device *dev,
-   struct intel_fbdev *ifbdev)
+static void intel_fbdev_destroy(struct intel_fbdev *ifbdev)
 {
/* We rely on the object-free to release the VMA pinning for
 * the info->screen_base mmaping. Leaking the VMA is simpler than
@@ -554,12 +553,14 @@ static void intel_fbdev_destroy(struct drm_device *dev,
if (ifbdev->fb) {
drm_framebuffer_unregister_private(>fb->base);
 
-   mutex_lock(>struct_mutex);
+   mutex_lock(>helper.dev->struct_mutex);
intel_unpin_fb_obj(>fb->base, BIT(DRM_ROTATE_0));
-   mutex_unlock(>struct_mutex);
+   mutex_unlock(>helper.dev->struct_mutex);
 
drm_framebuffer_remove(>fb->base);
}
+
+   kfree(ifbdev);
 }
 
 /*
@@ -736,32 +737,36 @@ int intel_fbdev_init(struct drm_device *dev)
 
 static void intel_fbdev_initial_config(void *data, async_cookie_t cookie)
 {
-   struct drm_i915_private *dev_priv = data;
-   struct intel_fbdev *ifbdev = dev_priv->fbdev;
+   struct intel_fbdev *ifbdev = data;
+
+   ifbdev->cookie = 0;
 
/* Due to peculiar init order wrt to hpd handling this is separate. */
if (drm_fb_helper_initial_config(>helper,
 ifbdev->preferred_bpp))
-   intel_fbdev_fini(dev_priv->dev);
+   intel_fbdev_fini(ifbdev->helper.dev);
 }
 
 void intel_fbdev_initial_config_async(struct drm_device *dev)
 {
-   async_schedule(intel_fbdev_initial_config, to_i915(dev));
+   struct intel_fbdev *ifbdev = to_i915(dev)->fbdev;
+
+   ifbdev->cookie = async_schedule(intel_fbdev_initial_config, ifbdev);
 }
 
 void intel_fbdev_fini(struct drm_device *dev)
 {
struct drm_i915_private *dev_priv = dev->dev_private;
-   if (!dev_priv->fbdev)
+   struct intel_fbdev *ifbdev = dev_priv->fbdev;
+
+   if (!ifbdev)
return;
 
flush_work(_priv->fbdev_suspend_work);
+   if (ifbdev->cookie && !current_is_async())
+   async_synchronize_cookie(ifbdev->cookie + 1);
 
-   if (!current_is_async())
-   async_synchronize_full();
-   intel_fbdev_destroy(dev, dev_priv->fbdev);
-   kfree(dev_priv->fbdev);
+   intel_fbdev_destroy(ifbdev);
dev_priv->fbdev = NULL;
 }
 
-- 
2.8.1

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