Re: [PATCH] drm/i915: Distinguish last emitted request from last submitted request

[Mika Kuoppala <mika.kuoppala@linux.intel.com>]

Chris Wilson <chris@chris-wilson.co.uk> writes:

> In order not to trigger hangcheck on a idle-but-waiting engine, we need
> to distinguish between the pending request queue and the actual
> execution queue. This is done later in "drm/i915: Enable multiple
> timelines" but for now we need a temporary fix to prevent blaming the
> wrong engine for a GPU hang.
>

You described this as a hack, but on top of current nightly,
this doesn't seem so hackish at all.

Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>

> Fixes: 0a046a0e93d2 ("drm/i915: Nonblocking request submission")
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
> Cc: Mika Kuoppala <mika.kuoppala@intel.com>
> ---
>  drivers/gpu/drm/i915/i915_gem_request.c | 5 +++--
>  drivers/gpu/drm/i915/intel_ringbuffer.h | 1 +
>  2 files changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem_request.c b/drivers/gpu/drm/i915/i915_gem_request.c
> index 40978bc12ceb..8832f8ec1583 100644
> --- a/drivers/gpu/drm/i915/i915_gem_request.c
> +++ b/drivers/gpu/drm/i915/i915_gem_request.c
> @@ -328,6 +328,7 @@ submit_notify(struct i915_sw_fence *fence, enum i915_sw_fence_notify state)
>  
>  	switch (state) {
>  	case FENCE_COMPLETE:
> +		request->engine->last_submitted_seqno = request->fence.seqno;
>  		request->engine->submit_request(request);
>  		break;
>  
> @@ -641,8 +642,8 @@ void __i915_add_request(struct drm_i915_gem_request *request, bool flush_caches)
>  					     &request->submitq);
>  
>  	request->emitted_jiffies = jiffies;
> -	request->previous_seqno = engine->last_submitted_seqno;
> -	engine->last_submitted_seqno = request->fence.seqno;
> +	request->previous_seqno = engine->last_pending_seqno;
> +	engine->last_pending_seqno = request->fence.seqno;
>  	i915_gem_active_set(&engine->last_request, request);
>  	list_add_tail(&request->link, &engine->request_list);
>  	list_add_tail(&request->ring_link, &ring->request_list);
> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
> index 498931f0b1f1..34954ca03a4a 100644
> --- a/drivers/gpu/drm/i915/intel_ringbuffer.h
> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
> @@ -355,6 +355,7 @@ struct intel_engine_cs {
>  	 * inspecting request list.
>  	 */
>  	u32 last_submitted_seqno;
> +	u32 last_pending_seqno;
>  
>  	/* An RCU guarded pointer to the last request. No reference is
>  	 * held to the request, users must carefully acquire a reference to
> -- 
> 2.9.3
>
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