[Intel-gfx] [PATCH 1/1] drm/vblank: drop use of DRM_WAIT_ON()

[Daniel Vetter]

On Thu, Jul 18, 2019 at 09:47:09PM +0200, Sam Ravnborg wrote:
> From e6f70cb90e0c3c90d45017a8257353652b7e0dcc Mon Sep 17 00:00:00 2001
> From: Sam Ravnborg <sam at ravnborg.org>
> Date: Thu, 30 May 2019 09:38:47 +0200
> Subject: [PATCH] drm/vblank: drop use of DRM_WAIT_ON()
> 
> DRM_WAIT_ON() is from the deprecated drm_os_linux header and
> the modern replacement is the wait_event_*.
> 
> The return values differ, so a conversion is needed to
> keep the original interface towards userspace.
> Introduced a switch/case to make code obvious and to allow
> different debug prints depending on the result.
> 
> Signed-off-by: Sam Ravnborg <sam at ravnborg.org>
> Reviewed-by: Sean Paul <sean at poorly.run>

A bit bold to keep the r-b for this substantial bugfix to the patch.

Also not per-patch changelog here. Plus doesn't seem to be on dri-devel
somehow.

> Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
> Cc: Maxime Ripard <maxime.ripard at bootlin.com>
> Cc: David Airlie <airlied at linux.ie>
> Cc: Daniel Vetter <daniel at ffwll.ch>
> ---
> 
> To verify if it works with the fix.
> (Added wat variable to handle the situation where we never wait)
> 
> 	Sam
> 
>  drivers/gpu/drm/drm_vblank.c | 32 ++++++++++++++++++++++----------
>  1 file changed, 22 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c
> index 603ab105125d..4e83f1dfd446 100644
> --- a/drivers/gpu/drm/drm_vblank.c
> +++ b/drivers/gpu/drm/drm_vblank.c
> @@ -31,7 +31,6 @@
>  #include <drm/drm_drv.h>
>  #include <drm/drm_framebuffer.h>
>  #include <drm/drm_print.h>
> -#include <drm/drm_os_linux.h>
>  #include <drm/drm_vblank.h>
>  
>  #include "drm_internal.h"
> @@ -1576,7 +1575,7 @@ int drm_wait_vblank_ioctl(struct drm_device *dev, void *data,
>  	struct drm_crtc *crtc;
>  	struct drm_vblank_crtc *vblank;
>  	union drm_wait_vblank *vblwait = data;
> -	int ret;
> +	int ret, wait;
>  	u64 req_seq, seq;
>  	unsigned int pipe_index;
>  	unsigned int flags, pipe, high_pipe;
> @@ -1669,22 +1668,35 @@ int drm_wait_vblank_ioctl(struct drm_device *dev, void *data,
>  		return drm_queue_vblank_event(dev, pipe, req_seq, vblwait, file_priv);
>  	}
>  
> +	wait = 1;

Instead of this hack I think better to remap the ret value in the if
condition. This here is really hard to read.
-Daniel

>  	if (req_seq != seq) {
>  		DRM_DEBUG("waiting on vblank count %llu, crtc %u\n",
>  			  req_seq, pipe);
> -		DRM_WAIT_ON(ret, vblank->queue, 3 * HZ,
> -			    vblank_passed(drm_vblank_count(dev, pipe),
> -					  req_seq) ||
> -			    !READ_ONCE(vblank->enabled));
> +		wait = wait_event_interruptible_timeout(vblank->queue,
> +			vblank_passed(drm_vblank_count(dev, pipe), req_seq) ||
> +				      !READ_ONCE(vblank->enabled),
> +			msecs_to_jiffies(3000));
>  	}
>  
> -	if (ret != -EINTR) {
> +	switch (wait) {
> +	case 0:
> +		/* timeout */
> +		ret = -EBUSY;
>  		drm_wait_vblank_reply(dev, pipe, &vblwait->reply);
> -
> -		DRM_DEBUG("crtc %d returning %u to client\n",
> +		DRM_DEBUG("timeout waiting for vblank. crtc %d returning %u to client\n",
>  			  pipe, vblwait->reply.sequence);
> -	} else {
> +		break;
> +	case -ERESTARTSYS:
> +		/* interrupted by signal */
> +		ret = -EINTR;
>  		DRM_DEBUG("crtc %d vblank wait interrupted by signal\n", pipe);
> +		break;
> +	default:
> +		ret = 0;
> +		drm_wait_vblank_reply(dev, pipe, &vblwait->reply);
> +		DRM_DEBUG("crtc %d returning %u to client\n",
> +			  pipe, vblwait->reply.sequence);
> +		break;
>  	}
>  
>  done:
> -- 
> 2.20.1
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch