linux-kernel - Re: [PATCH 4/5] drm/vblank: Use spin_(un)lock_irq() in drm_queue_vblank

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Date:   Tue, 21 Jul 2020 08:50:58 +0200
From:   Daniel Vetter <daniel@...ll.ch>
To:     Lyude Paul <lyude@...hat.com>
Cc:     dri-devel@...ts.freedesktop.org, Daniel Vetter <daniel@...ll.ch>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...ux.ie>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/5] drm/vblank: Use spin_(un)lock_irq() in
 drm_queue_vblank_event()

On Mon, Jul 20, 2020 at 03:07:35PM -0400, Lyude Paul wrote:
> This one's easy - we're already calling kzalloc() in this function, so

Nit: "kzalloc(GFP_KERNEL)", since kzalloc(GFP_ATOMIC) is perfectly fine in
interrupt context. With that clarified for the entire series:

Reviewed-by: Daniel Vetter <daniel.vetter@...ll.ch>

> we must already be guaranteed to have IRQs enabled when calling this.
> So, use the plain _irq() variants of spin_(un)lock() to make this more
> obvious.
> 
> Signed-off-by: Lyude Paul <lyude@...hat.com>
> Cc: Daniel Vetter <daniel@...ll.ch>
> ---
>  drivers/gpu/drm/drm_vblank.c | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c
> index 51f2e988205e7..64610070ba473 100644
> --- a/drivers/gpu/drm/drm_vblank.c
> +++ b/drivers/gpu/drm/drm_vblank.c
> @@ -1611,7 +1611,6 @@ static int drm_queue_vblank_event(struct drm_device *dev, unsigned int pipe,
>  	struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
>  	struct drm_pending_vblank_event *e;
>  	ktime_t now;
> -	unsigned long flags;
>  	u64 seq;
>  	int ret;
>  
> @@ -1633,7 +1632,7 @@ static int drm_queue_vblank_event(struct drm_device *dev, unsigned int pipe,
>  			e->event.vbl.crtc_id = crtc->base.id;
>  	}
>  
> -	spin_lock_irqsave(&dev->event_lock, flags);
> +	spin_lock_irq(&dev->event_lock);
>  
>  	/*
>  	 * drm_crtc_vblank_off() might have been called after we called
> @@ -1670,12 +1669,12 @@ static int drm_queue_vblank_event(struct drm_device *dev, unsigned int pipe,
>  		vblwait->reply.sequence = req_seq;
>  	}
>  
> -	spin_unlock_irqrestore(&dev->event_lock, flags);
> +	spin_unlock_irq(&dev->event_lock);
>  
>  	return 0;
>  
>  err_unlock:
> -	spin_unlock_irqrestore(&dev->event_lock, flags);
> +	spin_unlock_irq(&dev->event_lock);
>  	kfree(e);
>  err_put:
>  	drm_vblank_put(dev, pipe);
> -- 
> 2.26.2
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch