[Intel-gfx] [PATCH] drm/i915: Build request info on stack before printk

[Tvrtko Ursulin]

On 24/04/2018 02:08, Chris Wilson wrote:
> printk unhelpfully inserts a '\n' between consecutive calls, and since
> our drm_printf wrapper may be emitting info a seq_file instead,
> KERN_CONT is not an option. To work with any drm_printf destination, we
> need to build up the output into a temporary buf on the stack and then
> feed the complete line in a single call to printk.
> 
> Fixes: b7268c5eed0a ("drm/i915: Pack params to engine->schedule() into a struct")
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> ---
>   drivers/gpu/drm/i915/intel_engine_cs.c | 24 +++++++++++++++---------
>   1 file changed, 15 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_engine_cs.c b/drivers/gpu/drm/i915/intel_engine_cs.c
> index be608f7111f5..66cddd059666 100644
> --- a/drivers/gpu/drm/i915/intel_engine_cs.c
> +++ b/drivers/gpu/drm/i915/intel_engine_cs.c
> @@ -1113,14 +1113,17 @@ unsigned int intel_engines_has_context_isolation(struct drm_i915_private *i915)
>   	return which;
>   }
>   
> -static void print_sched_attr(struct drm_printer *m,
> -			     const struct drm_i915_private *i915,
> -			     const struct i915_sched_attr *attr)
> +static int print_sched_attr(struct drm_i915_private *i915,
> +			    const struct i915_sched_attr *attr,
> +			    char *buf, int x, int len)
>   {
>   	if (attr->priority == I915_PRIORITY_INVALID)
> -		return;
> +		return x;
> +
> +	x += snprintf(buf + x, len - x,
> +		      " prio=%d", attr->priority);
>   
> -	drm_printf(m, "prio=%d", attr->priority);
> +	return x;
>   }
>   
>   static void print_request(struct drm_printer *m,
> @@ -1128,14 +1131,17 @@ static void print_request(struct drm_printer *m,
>   			  const char *prefix)
>   {
>   	const char *name = rq->fence.ops->get_timeline_name(&rq->fence);
> +	char buf[80];

Worth using less stack space? 6 chars plus max negative int (12) - 18 
should be enough?

> +	int x = 0;
> +
> +	x = print_sched_attr(rq->i915, &rq->sched.attr, buf, x, sizeof(buf));

x is effectively unused. Drop it and simplify the helper and all?

>   
> -	drm_printf(m, "%s%x%s [%llx:%x] ",
> +	drm_printf(m, "%s%x%s [%llx:%x]%s @ %dms: %s\n",
>   		   prefix,
>   		   rq->global_seqno,
>   		   i915_request_completed(rq) ? "!" : "",
> -		   rq->fence.context, rq->fence.seqno);
> -	print_sched_attr(m, rq->i915, &rq->sched.attr);
> -	drm_printf(m, " @ %dms: %s\n",
> +		   rq->fence.context, rq->fence.seqno,
> +		   buf,
>   		   jiffies_to_msecs(jiffies - rq->emitted_jiffies),
>   		   name);
>   }
> 

Regards,

Tvrtko