Nouveau - Apr 2012 - [PATCH 2/5] drm/nouveau: base fence timeout on time of emission

Wait loop can be interrupted by signal, so if signals are raised
periodically (e.g. SIGALRM) this loop may never finish. Use
emission time as a base for fence timeout.

Signed-off-by: Marcin Slusarz <marcin.slusarz at gmail.com>
---
 drivers/gpu/drm/nouveau/nouveau_fence.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/nouveau_fence.c
b/drivers/gpu/drm/nouveau/nouveau_fence.c
index a22b9ad..59f92e9 100644
--- a/drivers/gpu/drm/nouveau/nouveau_fence.c
+++ b/drivers/gpu/drm/nouveau/nouveau_fence.c
@@ -44,6 +44,7 @@ struct nouveau_fence {
 
 	uint32_t sequence;
 	bool signalled;
+	unsigned long emitted_at;
 
 	void (*work)(void *priv, bool signalled);
 	void *priv;
@@ -172,6 +173,7 @@ nouveau_fence_emit(struct nouveau_fence *fence)
 	}
 	OUT_RING (chan, fence->sequence);
 	FIRE_RING(chan);
+	fence->emitted_at = jiffies;
 
 	return 0;
 }
@@ -230,7 +232,8 @@ __nouveau_fence_signalled(void *sync_obj, void *sync_arg)
 int
 __nouveau_fence_wait(void *sync_obj, void *sync_arg, bool lazy, bool intr)
 {
-	unsigned long timeout = jiffies + (3 * DRM_HZ);
+	struct nouveau_fence *fence = nouveau_fence(sync_obj);
+	unsigned long timeout = fence->emitted_at + 3 * DRM_HZ;
 	unsigned long sleep_time = NSEC_PER_MSEC / 1000;
 	ktime_t t;
 	int ret = 0;
-- 
1.7.8.5

On Mon, 2012-04-23 at 00:18 +0200, Marcin Slusarz wrote:
> Wait loop can be interrupted by signal, so if signals are raised
> periodically (e.g. SIGALRM) this loop may never finish. Use
> emission time as a base for fence timeout.
Ah, thanks for tackling this issue.  It's been long on my list of things
to do, but never quite made it to the top.

Rather than hardcoding the timeout in fence_wait(), I think perhaps
storing "fence->timeout = jiffies + (whatever * HZ);" is a better
plan.
I can forsee us wanting longer timeouts for certain operations
(particularly long compute operations) in the future.

Ben.
> 
> Signed-off-by: Marcin Slusarz <marcin.slusarz at gmail.com>
> ---
>  drivers/gpu/drm/nouveau/nouveau_fence.c |    5 ++++-
>  1 files changed, 4 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/gpu/drm/nouveau/nouveau_fence.c
b/drivers/gpu/drm/nouveau/nouveau_fence.c
> index a22b9ad..59f92e9 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_fence.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_fence.c
> @@ -44,6 +44,7 @@ struct nouveau_fence {
>  
>  	uint32_t sequence;
>  	bool signalled;
> +	unsigned long emitted_at;
>  
>  	void (*work)(void *priv, bool signalled);
>  	void *priv;
> @@ -172,6 +173,7 @@ nouveau_fence_emit(struct nouveau_fence *fence)
>  	}
>  	OUT_RING (chan, fence->sequence);
>  	FIRE_RING(chan);
> +	fence->emitted_at = jiffies;
>  
>  	return 0;
>  }
> @@ -230,7 +232,8 @@ __nouveau_fence_signalled(void *sync_obj, void
*sync_arg)
>  int
>  __nouveau_fence_wait(void *sync_obj, void *sync_arg, bool lazy, bool intr)
>  {
> -	unsigned long timeout = jiffies + (3 * DRM_HZ);
> +	struct nouveau_fence *fence = nouveau_fence(sync_obj);
> +	unsigned long timeout = fence->emitted_at + 3 * DRM_HZ;
>  	unsigned long sleep_time = NSEC_PER_MSEC / 1000;
>  	ktime_t t;
>  	int ret = 0;