drm: Clean up pending events in the core
diff mbox

Message ID 1452346126-20091-1-git-send-email-daniel.vetter@ffwll.ch
State New
Headers show

Commit Message

Daniel Vetter Jan. 9, 2016, 1:28 p.m. UTC
There's really no reason to not do so, instead of replicating this
for every use-case and every driver. Now we can't just nuke the events,
since that would still mean that all drm_event users would need to know
when that has happened, since calling e.g. drm_send_event isn't allowed
any more. Instead just unlink them from the file, and detect this case
and handle it appropriately in all functions.

v2: Adjust existing kerneldoc too.

Cc: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
---
 drivers/gpu/drm/drm_fops.c | 35 ++++++++++++++++++++++++++---------
 include/drm/drmP.h         |  2 ++
 2 files changed, 28 insertions(+), 9 deletions(-)

Comments

Laurent Pinchart Jan. 10, 2016, 11:48 p.m. UTC | #1
Hi Daniel,

Thank you for the patch.

On Saturday 09 January 2016 14:28:46 Daniel Vetter wrote:
> There's really no reason to not do so, instead of replicating this
> for every use-case and every driver. Now we can't just nuke the events,
> since that would still mean that all drm_event users would need to know
> when that has happened, since calling e.g. drm_send_event isn't allowed
> any more. Instead just unlink them from the file, and detect this case
> and handle it appropriately in all functions.
> 
> v2: Adjust existing kerneldoc too.
> 
> Cc: Alex Deucher <alexander.deucher@amd.com>
> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> ---
>  drivers/gpu/drm/drm_fops.c | 35 ++++++++++++++++++++++++++---------
>  include/drm/drmP.h         |  2 ++
>  2 files changed, 28 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_fops.c b/drivers/gpu/drm/drm_fops.c
> index d85af1b2a238..d32b24c74e08 100644
> --- a/drivers/gpu/drm/drm_fops.c
> +++ b/drivers/gpu/drm/drm_fops.c
> @@ -264,6 +264,7 @@ static int drm_open_helper(struct file *filp, struct
> drm_minor *minor) INIT_LIST_HEAD(&priv->fbs);
>  	mutex_init(&priv->fbs_lock);
>  	INIT_LIST_HEAD(&priv->blobs);
> +	INIT_LIST_HEAD(&priv->pending_event_list);
>  	INIT_LIST_HEAD(&priv->event_list);
>  	init_waitqueue_head(&priv->event_wait);
>  	priv->event_space = 4096; /* set aside 4k for event buffer */
> @@ -353,18 +354,16 @@ static void drm_events_release(struct drm_file
> *file_priv) {
>  	struct drm_device *dev = file_priv->minor->dev;
>  	struct drm_pending_event *e, *et;
> -	struct drm_pending_vblank_event *v, *vt;
>  	unsigned long flags;
> 
>  	spin_lock_irqsave(&dev->event_lock, flags);
> 
> -	/* Remove pending flips */
> -	list_for_each_entry_safe(v, vt, &dev->vblank_event_list, base.link)
> -		if (v->base.file_priv == file_priv) {
> -			list_del(&v->base.link);
> -			drm_vblank_put(dev, v->pipe);
> -			v->base.destroy(&v->base);
> -		}

Where does this code go ?

> +	/* Unlink pending events */
> +	list_for_each_entry_safe(e, et, &file_priv->pending_event_list,
> +				 pending_link) {
> +		list_del(&e->pending_link);
> +		e->file_priv = NULL;
> +	}
> 
>  	/* Remove unconsumed events */
>  	list_for_each_entry_safe(e, et, &file_priv->event_list, link) {
> @@ -712,6 +711,7 @@ int drm_event_reserve_init(struct drm_device *dev,
>  	file_priv->event_space -= e->length;
> 
>  	p->event = e;
> +	list_add(&p->pending_link, &file_priv->pending_event_list);
>  	p->file_priv = file_priv;
> 
>  	/* we *could* pass this in as arg, but everyone uses kfree: */
> @@ -736,7 +736,10 @@ void drm_event_cancel_free(struct drm_device *dev,
>  {
>  	unsigned long flags;
>  	spin_lock_irqsave(&dev->event_lock, flags);
> -	p->file_priv->event_space += p->event->length;
> +	if (p->file_priv) {
> +		p->file_priv->event_space += p->event->length;
> +		list_del(&p->pending_link);
> +	}
>  	spin_unlock_irqrestore(&dev->event_lock, flags);
>  	p->destroy(p);
>  }
> @@ -750,11 +753,21 @@ EXPORT_SYMBOL(drm_event_cancel_free);
>   * This function sends the event @e, initialized with
> drm_event_reserve_init(),
>   * to its associated userspace DRM file. Callers must already hold
>   * dev->event_lock, see drm_send_event() for the unlocked version.
> + *
> + * Note that the core will take care of unlinking and disarming events when
> the
> + * corresponding DRM file is closed. Drivers need to worry about that and

s/need to/need not/ ?

> can
> + * call this function upon completion of the asynchrnous work

s/asynchrnous/asynchronous/

> unconditionally. */
>  void drm_send_event_locked(struct drm_device *dev, struct drm_pending_event
> *e) {
>  	assert_spin_locked(&dev->event_lock);
> 
> +	if (!e->file_priv) {

I don't think this could happen before this patch as e->file_priv is 
dereferenced below, and I don't see anything in this patch that makes the 
condition possible.

> +		e->destroy(e);
> +		return;
> +	}
> +
> +	list_del(&e->pending_link);
>  	list_add_tail(&e->link,
>  		      &e->file_priv->event_list);
>  	wake_up_interruptible(&e->file_priv->event_wait);
> @@ -769,6 +782,10 @@ EXPORT_SYMBOL(drm_send_event_locked);
>   * This function sends the event @e, initialized with
> drm_event_reserve_init(),
>   * to its associated userspace DRM file. This function acquires
> dev->event_lock,
>   * see drm_send_event_locked() for callers which already hold this lock.
> + *
> + * Note that the core will take care of unlinking and disarming events when
> the
> + * corresponding DRM file is closed. Drivers need to worry about that and

s/need to/need not/ ?

> can
> + * call this function upon completion of the asynchrnous work

s/asynchrnous/asynchronous/

> unconditionally. */
>  void drm_send_event(struct drm_device *dev, struct drm_pending_event *e)
>  {
> diff --git a/include/drm/drmP.h b/include/drm/drmP.h
> index ae73abf5c2cf..3d78a7406d54 100644
> --- a/include/drm/drmP.h
> +++ b/include/drm/drmP.h
> @@ -283,6 +283,7 @@ struct drm_ioctl_desc {
>  struct drm_pending_event {
>  	struct drm_event *event;
>  	struct list_head link;
> +	struct list_head pending_link;
>  	struct drm_file *file_priv;
>  	pid_t pid; /* pid of requester, no guarantee it's valid by the time
>  		      we deliver the event, for tracing only */
> @@ -346,6 +347,7 @@ struct drm_file {
>  	struct list_head blobs;
> 
>  	wait_queue_head_t event_wait;
> +	struct list_head pending_event_list;
>  	struct list_head event_list;
>  	int event_space;
Daniel Stone Jan. 11, 2016, 2:51 p.m. UTC | #2
Hi,

On 10 January 2016 at 23:48, Laurent Pinchart
<laurent.pinchart@ideasonboard.com> wrote:
> On Saturday 09 January 2016 14:28:46 Daniel Vetter wrote:
>> @@ -353,18 +354,16 @@ static void drm_events_release(struct drm_file
>> *file_priv) {
>>       struct drm_device *dev = file_priv->minor->dev;
>>       struct drm_pending_event *e, *et;
>> -     struct drm_pending_vblank_event *v, *vt;
>>       unsigned long flags;
>>
>>       spin_lock_irqsave(&dev->event_lock, flags);
>>
>> -     /* Remove pending flips */
>> -     list_for_each_entry_safe(v, vt, &dev->vblank_event_list, base.link)
>> -             if (v->base.file_priv == file_priv) {
>> -                     list_del(&v->base.link);
>> -                     drm_vblank_put(dev, v->pipe);
>> -                     v->base.destroy(&v->base);
>> -             }
>
> Where does this code go ?

It doesn't: instead of deleting the events, the helpers to either
cancel or send the event just notice that file_priv is NULL and bail
out early.

>> +     /* Unlink pending events */
>> +     list_for_each_entry_safe(e, et, &file_priv->pending_event_list,
>> +                              pending_link) {
>> +             list_del(&e->pending_link);
>> +             e->file_priv = NULL;
>> +     }

file_priv gets reset here ...

>> @@ -736,7 +736,10 @@ void drm_event_cancel_free(struct drm_device *dev,
>>  {
>>       unsigned long flags;
>>       spin_lock_irqsave(&dev->event_lock, flags);
>> -     p->file_priv->event_space += p->event->length;
>> +     if (p->file_priv) {
>> +             p->file_priv->event_space += p->event->length;
>> +             list_del(&p->pending_link);
>> +     }
>>       spin_unlock_irqrestore(&dev->event_lock, flags);
>>       p->destroy(p);


Allowing us to DTRT here ...

>>  void drm_send_event_locked(struct drm_device *dev, struct drm_pending_event
>> *e) {
>>       assert_spin_locked(&dev->event_lock);
>>
>> +     if (!e->file_priv) {
>
> I don't think this could happen before this patch as e->file_priv is
> dereferenced below, and I don't see anything in this patch that makes the
> condition possible.
>
>> +             e->destroy(e);
>> +             return;
>> +     }

... and now here.

This looks good to me, and a good sight better than doing it in every
driver. Still drowning in stuff after three weeks off though, so the
best I can offer for the series right now is:
Acked-by: Daniel Stone <daniels@collabora.com>

Cheers,
Daniel
Laurent Pinchart Jan. 14, 2016, 6:49 p.m. UTC | #3
Hi Daniel,

On Monday 11 January 2016 14:51:46 Daniel Stone wrote:
> On 10 January 2016 at 23:48, Laurent Pinchart wrote:
> > On Saturday 09 January 2016 14:28:46 Daniel Vetter wrote:
> >> @@ -353,18 +354,16 @@ static void drm_events_release(struct drm_file
> >> *file_priv) {
> >> 
> >>       struct drm_device *dev = file_priv->minor->dev;
> >>       struct drm_pending_event *e, *et;
> >> 
> >> -     struct drm_pending_vblank_event *v, *vt;
> >> 
> >>       unsigned long flags;
> >>       
> >>       spin_lock_irqsave(&dev->event_lock, flags);
> >> 
> >> -     /* Remove pending flips */
> >> -     list_for_each_entry_safe(v, vt, &dev->vblank_event_list, base.link)
> >> -             if (v->base.file_priv == file_priv) {
> >> -                     list_del(&v->base.link);
> >> -                     drm_vblank_put(dev, v->pipe);
> >> -                     v->base.destroy(&v->base);
> >> -             }
> > 
> > Where does this code go ?
> 
> It doesn't: instead of deleting the events, the helpers to either
> cancel or send the event just notice that file_priv is NULL and bail
> out early.

Thank you for the explanation. What bothered me was that the drm_vblank_put() 
call got dropped. With v2 of this patch series that splits that change to a 
separate patch it's easier to understand.

> >> +     /* Unlink pending events */
> >> +     list_for_each_entry_safe(e, et, &file_priv->pending_event_list,
> >> +                              pending_link) {
> >> +             list_del(&e->pending_link);
> >> +             e->file_priv = NULL;
> >> +     }
> 
> file_priv gets reset here ...
> 
> >> @@ -736,7 +736,10 @@ void drm_event_cancel_free(struct drm_device *dev,
> >> 
> >>  {
> >>  
> >>       unsigned long flags;
> >>       spin_lock_irqsave(&dev->event_lock, flags);
> >> 
> >> -     p->file_priv->event_space += p->event->length;
> >> +     if (p->file_priv) {
> >> +             p->file_priv->event_space += p->event->length;
> >> +             list_del(&p->pending_link);
> >> +     }
> >> 
> >>       spin_unlock_irqrestore(&dev->event_lock, flags);
> >>       p->destroy(p);
> 
> Allowing us to DTRT here ...
> 
> >>  void drm_send_event_locked(struct drm_device *dev, struct
> >>  drm_pending_event
> >> 
> >> *e) {
> >> 
> >>       assert_spin_locked(&dev->event_lock);
> >> 
> >> +     if (!e->file_priv) {
> > 
> > I don't think this could happen before this patch as e->file_priv is
> > dereferenced below, and I don't see anything in this patch that makes the
> > condition possible.
> > 
> >> +             e->destroy(e);
> >> +             return;
> >> +     }
> 
> ... and now here.
> 
> This looks good to me, and a good sight better than doing it in every
> driver. Still drowning in stuff after three weeks off though, so the
> best I can offer for the series right now is:
> Acked-by: Daniel Stone <daniels@collabora.com>

Patch
diff mbox

diff --git a/drivers/gpu/drm/drm_fops.c b/drivers/gpu/drm/drm_fops.c
index d85af1b2a238..d32b24c74e08 100644
--- a/drivers/gpu/drm/drm_fops.c
+++ b/drivers/gpu/drm/drm_fops.c
@@ -264,6 +264,7 @@  static int drm_open_helper(struct file *filp, struct drm_minor *minor)
 	INIT_LIST_HEAD(&priv->fbs);
 	mutex_init(&priv->fbs_lock);
 	INIT_LIST_HEAD(&priv->blobs);
+	INIT_LIST_HEAD(&priv->pending_event_list);
 	INIT_LIST_HEAD(&priv->event_list);
 	init_waitqueue_head(&priv->event_wait);
 	priv->event_space = 4096; /* set aside 4k for event buffer */
@@ -353,18 +354,16 @@  static void drm_events_release(struct drm_file *file_priv)
 {
 	struct drm_device *dev = file_priv->minor->dev;
 	struct drm_pending_event *e, *et;
-	struct drm_pending_vblank_event *v, *vt;
 	unsigned long flags;
 
 	spin_lock_irqsave(&dev->event_lock, flags);
 
-	/* Remove pending flips */
-	list_for_each_entry_safe(v, vt, &dev->vblank_event_list, base.link)
-		if (v->base.file_priv == file_priv) {
-			list_del(&v->base.link);
-			drm_vblank_put(dev, v->pipe);
-			v->base.destroy(&v->base);
-		}
+	/* Unlink pending events */
+	list_for_each_entry_safe(e, et, &file_priv->pending_event_list,
+				 pending_link) {
+		list_del(&e->pending_link);
+		e->file_priv = NULL;
+	}
 
 	/* Remove unconsumed events */
 	list_for_each_entry_safe(e, et, &file_priv->event_list, link) {
@@ -712,6 +711,7 @@  int drm_event_reserve_init(struct drm_device *dev,
 	file_priv->event_space -= e->length;
 
 	p->event = e;
+	list_add(&p->pending_link, &file_priv->pending_event_list);
 	p->file_priv = file_priv;
 
 	/* we *could* pass this in as arg, but everyone uses kfree: */
@@ -736,7 +736,10 @@  void drm_event_cancel_free(struct drm_device *dev,
 {
 	unsigned long flags;
 	spin_lock_irqsave(&dev->event_lock, flags);
-	p->file_priv->event_space += p->event->length;
+	if (p->file_priv) {
+		p->file_priv->event_space += p->event->length;
+		list_del(&p->pending_link);
+	}
 	spin_unlock_irqrestore(&dev->event_lock, flags);
 	p->destroy(p);
 }
@@ -750,11 +753,21 @@  EXPORT_SYMBOL(drm_event_cancel_free);
  * This function sends the event @e, initialized with drm_event_reserve_init(),
  * to its associated userspace DRM file. Callers must already hold
  * dev->event_lock, see drm_send_event() for the unlocked version.
+ *
+ * Note that the core will take care of unlinking and disarming events when the
+ * corresponding DRM file is closed. Drivers need to worry about that and can
+ * call this function upon completion of the asynchrnous work unconditionally.
  */
 void drm_send_event_locked(struct drm_device *dev, struct drm_pending_event *e)
 {
 	assert_spin_locked(&dev->event_lock);
 
+	if (!e->file_priv) {
+		e->destroy(e);
+		return;
+	}
+
+	list_del(&e->pending_link);
 	list_add_tail(&e->link,
 		      &e->file_priv->event_list);
 	wake_up_interruptible(&e->file_priv->event_wait);
@@ -769,6 +782,10 @@  EXPORT_SYMBOL(drm_send_event_locked);
  * This function sends the event @e, initialized with drm_event_reserve_init(),
  * to its associated userspace DRM file. This function acquires dev->event_lock,
  * see drm_send_event_locked() for callers which already hold this lock.
+ *
+ * Note that the core will take care of unlinking and disarming events when the
+ * corresponding DRM file is closed. Drivers need to worry about that and can
+ * call this function upon completion of the asynchrnous work unconditionally.
  */
 void drm_send_event(struct drm_device *dev, struct drm_pending_event *e)
 {
diff --git a/include/drm/drmP.h b/include/drm/drmP.h
index ae73abf5c2cf..3d78a7406d54 100644
--- a/include/drm/drmP.h
+++ b/include/drm/drmP.h
@@ -283,6 +283,7 @@  struct drm_ioctl_desc {
 struct drm_pending_event {
 	struct drm_event *event;
 	struct list_head link;
+	struct list_head pending_link;
 	struct drm_file *file_priv;
 	pid_t pid; /* pid of requester, no guarantee it's valid by the time
 		      we deliver the event, for tracing only */
@@ -346,6 +347,7 @@  struct drm_file {
 	struct list_head blobs;
 
 	wait_queue_head_t event_wait;
+	struct list_head pending_event_list;
 	struct list_head event_list;
 	int event_space;