Some processes, such as systemd, are only polling for EPOLLERR|EPOLLHUP.
As drm_file uses unkeyed wakeups, such a poll can receive many spurious
wakeups from uninteresting events if, for example, the file description
is subscribed to vblank events. This is the case with systemd, as it
polls a file description from logind that is shared with the users'
compositor.
Use keyed wakeups to allow the wakeup target to more efficiently discard
these uninteresting events.
Signed-off-by: Kenny Levinsen <[email protected]>
---
drivers/gpu/drm/drm_file.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/drm_file.c b/drivers/gpu/drm/drm_file.c
index c4c704e01961..ec25b3d979d9 100644
--- a/drivers/gpu/drm/drm_file.c
+++ b/drivers/gpu/drm/drm_file.c
@@ -608,7 +608,8 @@ ssize_t drm_read(struct file *filp, char __user *buffer,
file_priv->event_space -= length;
list_add(&e->link, &file_priv->event_list);
spin_unlock_irq(&dev->event_lock);
- wake_up_interruptible(&file_priv->event_wait);
+ wake_up_interruptible_poll(&file_priv->event_wait,
+ EPOLLIN | EPOLLRDNORM);
break;
}
@@ -804,7 +805,8 @@ void drm_send_event_locked(struct drm_device *dev, struct drm_pending_event *e)
list_del(&e->pending_link);
list_add_tail(&e->link,
&e->file_priv->event_list);
- wake_up_interruptible(&e->file_priv->event_wait);
+ wake_up_interruptible_poll(&e->file_priv->event_wait,
+ EPOLLIN | EPOLLRDNORM);
}
EXPORT_SYMBOL(drm_send_event_locked);
--
2.26.1
On Fri, Apr 24, 2020 at 06:26:15PM +0200, Kenny Levinsen wrote:
> Some processes, such as systemd, are only polling for EPOLLERR|EPOLLHUP.
> As drm_file uses unkeyed wakeups, such a poll can receive many spurious
> wakeups from uninteresting events if, for example, the file description
> is subscribed to vblank events. This is the case with systemd, as it
> polls a file description from logind that is shared with the users'
> compositor.
>
> Use keyed wakeups to allow the wakeup target to more efficiently discard
> these uninteresting events.
>
> Signed-off-by: Kenny Levinsen <[email protected]>
Hm I applied v1 and I'm not spotting what's different here, and there's no
changelog explaining what changed ...
Please send a fixup if there's anything important missing.
-Daniel
> ---
> drivers/gpu/drm/drm_file.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_file.c b/drivers/gpu/drm/drm_file.c
> index c4c704e01961..ec25b3d979d9 100644
> --- a/drivers/gpu/drm/drm_file.c
> +++ b/drivers/gpu/drm/drm_file.c
> @@ -608,7 +608,8 @@ ssize_t drm_read(struct file *filp, char __user *buffer,
> file_priv->event_space -= length;
> list_add(&e->link, &file_priv->event_list);
> spin_unlock_irq(&dev->event_lock);
> - wake_up_interruptible(&file_priv->event_wait);
> + wake_up_interruptible_poll(&file_priv->event_wait,
> + EPOLLIN | EPOLLRDNORM);
> break;
> }
>
> @@ -804,7 +805,8 @@ void drm_send_event_locked(struct drm_device *dev, struct drm_pending_event *e)
> list_del(&e->pending_link);
> list_add_tail(&e->link,
> &e->file_priv->event_list);
> - wake_up_interruptible(&e->file_priv->event_wait);
> + wake_up_interruptible_poll(&e->file_priv->event_wait,
> + EPOLLIN | EPOLLRDNORM);
> }
> EXPORT_SYMBOL(drm_send_event_locked);
>
> --
> 2.26.1
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
April 28, 2020 5:14 PM, "Daniel Vetter" <[email protected]> wrote:
> On Fri, Apr 24, 2020 at 06:26:15PM +0200, Kenny Levinsen wrote:
>
>> Some processes, such as systemd, are only polling for EPOLLERR|EPOLLHUP.
>> As drm_file uses unkeyed wakeups, such a poll can receive many spurious
>> wakeups from uninteresting events if, for example, the file description
>> is subscribed to vblank events. This is the case with systemd, as it
>> polls a file description from logind that is shared with the users'
>> compositor.
>>
>> Use keyed wakeups to allow the wakeup target to more efficiently discard
>> these uninteresting events.
>>
>> Signed-off-by: Kenny Levinsen <[email protected]>
>
> Hm I applied v1 and I'm not spotting what's different here, and there's no
> changelog explaining what changed ...
>
> Please send a fixup if there's anything important missing.
> -Daniel
>
It's only the summary that differed as you and sravn requested in #dri-devel, so it's probably fine.
I should have explained the change. I'm still trying to get the hang of the email-based workflow. :)
Best regards,
Kenny Levinsen
>> ---
>> drivers/gpu/drm/drm_file.c | 6 ++++--
>> 1 file changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/drm_file.c b/drivers/gpu/drm/drm_file.c
>> index c4c704e01961..ec25b3d979d9 100644
>> --- a/drivers/gpu/drm/drm_file.c
>> +++ b/drivers/gpu/drm/drm_file.c
>> @@ -608,7 +608,8 @@ ssize_t drm_read(struct file *filp, char __user *buffer,
>> file_priv->event_space -= length;
>> list_add(&e->link, &file_priv->event_list);
>> spin_unlock_irq(&dev->event_lock);
>> - wake_up_interruptible(&file_priv->event_wait);
>> + wake_up_interruptible_poll(&file_priv->event_wait,
>> + EPOLLIN | EPOLLRDNORM);
>> break;
>> }
>>
>> @@ -804,7 +805,8 @@ void drm_send_event_locked(struct drm_device *dev, struct drm_pending_event *e)
>> list_del(&e->pending_link);
>> list_add_tail(&e->link,
>> &e->file_priv->event_list);
>> - wake_up_interruptible(&e->file_priv->event_wait);
>> + wake_up_interruptible_poll(&e->file_priv->event_wait,
>> + EPOLLIN | EPOLLRDNORM);
>> }
>> EXPORT_SYMBOL(drm_send_event_locked);
>>
>> --
>> 2.26.1
>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch
On Wed, Apr 29, 2020 at 11:19:07AM +0000, [email protected] wrote:
> April 28, 2020 5:14 PM, "Daniel Vetter" <[email protected]> wrote:
>
> > On Fri, Apr 24, 2020 at 06:26:15PM +0200, Kenny Levinsen wrote:
> >
> >> Some processes, such as systemd, are only polling for EPOLLERR|EPOLLHUP.
> >> As drm_file uses unkeyed wakeups, such a poll can receive many spurious
> >> wakeups from uninteresting events if, for example, the file description
> >> is subscribed to vblank events. This is the case with systemd, as it
> >> polls a file description from logind that is shared with the users'
> >> compositor.
> >>
> >> Use keyed wakeups to allow the wakeup target to more efficiently discard
> >> these uninteresting events.
> >>
> >> Signed-off-by: Kenny Levinsen <[email protected]>
> >
> > Hm I applied v1 and I'm not spotting what's different here, and there's no
> > changelog explaining what changed ...
> >
> > Please send a fixup if there's anything important missing.
> > -Daniel
> >
>
> It's only the summary that differed as you and sravn requested in #dri-devel, so it's probably fine.
>
> I should have explained the change. I'm still trying to get the hang of the email-based workflow. :)
Oops sorry, I generally run as a stateless maintainer so forgot :-/
And yes email based workflow is full of warts, it's a pain.
-Daniel
>
> Best regards,
> Kenny Levinsen
>
> >> ---
> >> drivers/gpu/drm/drm_file.c | 6 ++++--
> >> 1 file changed, 4 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/drivers/gpu/drm/drm_file.c b/drivers/gpu/drm/drm_file.c
> >> index c4c704e01961..ec25b3d979d9 100644
> >> --- a/drivers/gpu/drm/drm_file.c
> >> +++ b/drivers/gpu/drm/drm_file.c
> >> @@ -608,7 +608,8 @@ ssize_t drm_read(struct file *filp, char __user *buffer,
> >> file_priv->event_space -= length;
> >> list_add(&e->link, &file_priv->event_list);
> >> spin_unlock_irq(&dev->event_lock);
> >> - wake_up_interruptible(&file_priv->event_wait);
> >> + wake_up_interruptible_poll(&file_priv->event_wait,
> >> + EPOLLIN | EPOLLRDNORM);
> >> break;
> >> }
> >>
> >> @@ -804,7 +805,8 @@ void drm_send_event_locked(struct drm_device *dev, struct drm_pending_event *e)
> >> list_del(&e->pending_link);
> >> list_add_tail(&e->link,
> >> &e->file_priv->event_list);
> >> - wake_up_interruptible(&e->file_priv->event_wait);
> >> + wake_up_interruptible_poll(&e->file_priv->event_wait,
> >> + EPOLLIN | EPOLLRDNORM);
> >> }
> >> EXPORT_SYMBOL(drm_send_event_locked);
> >>
> >> --
> >> 2.26.1
> >
> > --
> > Daniel Vetter
> > Software Engineer, Intel Corporation
> > http://blog.ffwll.ch
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch