linux-kernel - Re: [PATCH v2] drm: make drm

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Date:   Thu, 30 Apr 2020 16:04:16 +0200
From:   Daniel Vetter <daniel@...ll.ch>
To:     kl@...wtf
Cc:     Daniel Vetter <daniel@...ll.ch>, intel-gfx@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org, airlied@...ux.ie,
        tzimmermann@...e.de, mripard@...nel.org,
        maarten.lankhorst@...ux.intel.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] drm: make drm_file use keyed wakeups

On Wed, Apr 29, 2020 at 11:19:07AM +0000, kl@...wtf wrote:
> April 28, 2020 5:14 PM, "Daniel Vetter" <daniel@...ll.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@...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. :)

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