[PATCH v2] drm: make drm_file use keyed wakeups

[kl at kl.wtf]

April 28, 2020 5:14 PM, "Daniel Vetter" <daniel at ffwll.ch> 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 <kl at kl.wtf>
> 
> 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