[Intel-gfx] [PATCH] drm/i915/guc: Keep irq enabled during GuC cmd submission

[Daniel Vetter]

On Thu, Nov 19, 2015 at 04:15:22PM -0800, yu.dai at intel.com wrote:
> From: Alex Dai <yu.dai at intel.com>
> 
> When GuC Work Queue is full, driver will wait GuC for avaliable
> space by calling wait_for_atomic. If irq is disabled, lockup will
> happen because jiffies won't be updated.
> 
> Issue is found in igt/gem_close_race.
> 
> Signed-off-by: Alex Dai <yu.dai at intel.com>
> ---
>  drivers/gpu/drm/i915/i915_guc_submission.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_guc_submission.c b/drivers/gpu/drm/i915/i915_guc_submission.c
> index 0a6b007..bbfa6ed 100644
> --- a/drivers/gpu/drm/i915/i915_guc_submission.c
> +++ b/drivers/gpu/drm/i915/i915_guc_submission.c
> @@ -597,14 +597,13 @@ int i915_guc_submit(struct i915_guc_client *client,
>  {
>  	struct intel_guc *guc = client->guc;
>  	enum intel_ring_id ring_id = rq->ring->id;
> -	unsigned long flags;
>  	int q_ret, b_ret;
>  
>  	/* Need this because of the deferred pin ctx and ring */
>  	/* Shall we move this right after ring is pinned? */
>  	lr_context_update(rq);
>  
> -	spin_lock_irqsave(&client->wq_lock, flags);
> +	spin_lock(&client->wq_lock);

Oh dear your busy-spinning for the hw under a spinlock. That's horribly
broken design, please fix this asap. _irqsave is the least of your
concerns here.
-Daniel

>  
>  	q_ret = guc_add_workqueue_item(client, rq);
>  	if (q_ret == 0)
> @@ -620,7 +619,7 @@ int i915_guc_submit(struct i915_guc_client *client,
>  	} else {
>  		client->retcode = 0;
>  	}
> -	spin_unlock_irqrestore(&client->wq_lock, flags);
> +	spin_unlock(&client->wq_lock);
>  
>  	spin_lock(&guc->host2guc_lock);
>  	guc->submissions[ring_id] += 1;
> -- 
> 2.5.0
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch