Re: [Intel-gfx] [PATCH 17/22] drm/i915/guc: Move guc_blocked fence to struct guc_state

[Daniel Vetter <daniel@ffwll.ch>]

On Mon, Aug 16, 2021 at 06:51:34AM -0700, Matthew Brost wrote:
> Move guc_blocked fence to struct guc_state as the lock which protects
> the fence lives there.
> 
> s/ce->guc_blocked/ce->guc_state.blocked_fence/g
> 
> Signed-off-by: Matthew Brost <matthew.brost@intel.com>

General comment, but latest when your combine your count state with a wait
queue you're very far into "reinventing a mutex/semaphore, badly" land.

I think we really need to look into why we can't just protect this all
with a mutex and make sure the awkward transition states are never visible
to anyone else.
-Daniel

> ---
>  drivers/gpu/drm/i915/gt/intel_context.c        |  5 +++--
>  drivers/gpu/drm/i915/gt/intel_context_types.h  |  5 ++---
>  .../gpu/drm/i915/gt/uc/intel_guc_submission.c  | 18 +++++++++---------
>  3 files changed, 14 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/gt/intel_context.c b/drivers/gpu/drm/i915/gt/intel_context.c
> index 745e84c72c90..0e48939ec85f 100644
> --- a/drivers/gpu/drm/i915/gt/intel_context.c
> +++ b/drivers/gpu/drm/i915/gt/intel_context.c
> @@ -405,8 +405,9 @@ intel_context_init(struct intel_context *ce, struct intel_engine_cs *engine)
>  	 * Initialize fence to be complete as this is expected to be complete
>  	 * unless there is a pending schedule disable outstanding.
>  	 */
> -	i915_sw_fence_init(&ce->guc_blocked, sw_fence_dummy_notify);
> -	i915_sw_fence_commit(&ce->guc_blocked);
> +	i915_sw_fence_init(&ce->guc_state.blocked_fence,
> +			   sw_fence_dummy_notify);
> +	i915_sw_fence_commit(&ce->guc_state.blocked_fence);
>  
>  	i915_active_init(&ce->active,
>  			 __intel_context_active, __intel_context_retire, 0);
> diff --git a/drivers/gpu/drm/i915/gt/intel_context_types.h b/drivers/gpu/drm/i915/gt/intel_context_types.h
> index 3a73f3117873..c06171ee8792 100644
> --- a/drivers/gpu/drm/i915/gt/intel_context_types.h
> +++ b/drivers/gpu/drm/i915/gt/intel_context_types.h
> @@ -167,6 +167,8 @@ struct intel_context {
>  		 * fence related to GuC submission
>  		 */
>  		struct list_head fences;
> +		/* GuC context blocked fence */
> +		struct i915_sw_fence blocked_fence;
>  	} guc_state;
>  
>  	struct {
> @@ -190,9 +192,6 @@ struct intel_context {
>  	 */
>  	struct list_head guc_id_link;
>  
> -	/* GuC context blocked fence */
> -	struct i915_sw_fence guc_blocked;
> -
>  	/*
>  	 * GuC priority management
>  	 */
> diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> index 9ae4633aa7cb..7aa16371908a 100644
> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> @@ -1482,24 +1482,24 @@ static void guc_blocked_fence_complete(struct intel_context *ce)
>  {
>  	lockdep_assert_held(&ce->guc_state.lock);
>  
> -	if (!i915_sw_fence_done(&ce->guc_blocked))
> -		i915_sw_fence_complete(&ce->guc_blocked);
> +	if (!i915_sw_fence_done(&ce->guc_state.blocked_fence))
> +		i915_sw_fence_complete(&ce->guc_state.blocked_fence);
>  }
>  
>  static void guc_blocked_fence_reinit(struct intel_context *ce)
>  {
>  	lockdep_assert_held(&ce->guc_state.lock);
> -	GEM_BUG_ON(!i915_sw_fence_done(&ce->guc_blocked));
> +	GEM_BUG_ON(!i915_sw_fence_done(&ce->guc_state.blocked_fence));
>  
>  	/*
>  	 * This fence is always complete unless a pending schedule disable is
>  	 * outstanding. We arm the fence here and complete it when we receive
>  	 * the pending schedule disable complete message.
>  	 */
> -	i915_sw_fence_fini(&ce->guc_blocked);
> -	i915_sw_fence_reinit(&ce->guc_blocked);
> -	i915_sw_fence_await(&ce->guc_blocked);
> -	i915_sw_fence_commit(&ce->guc_blocked);
> +	i915_sw_fence_fini(&ce->guc_state.blocked_fence);
> +	i915_sw_fence_reinit(&ce->guc_state.blocked_fence);
> +	i915_sw_fence_await(&ce->guc_state.blocked_fence);
> +	i915_sw_fence_commit(&ce->guc_state.blocked_fence);
>  }
>  
>  static u16 prep_context_pending_disable(struct intel_context *ce)
> @@ -1539,7 +1539,7 @@ static struct i915_sw_fence *guc_context_block(struct intel_context *ce)
>  		if (enabled)
>  			clr_context_enabled(ce);
>  		spin_unlock_irqrestore(&ce->guc_state.lock, flags);
> -		return &ce->guc_blocked;
> +		return &ce->guc_state.blocked_fence;
>  	}
>  
>  	/*
> @@ -1555,7 +1555,7 @@ static struct i915_sw_fence *guc_context_block(struct intel_context *ce)
>  	with_intel_runtime_pm(runtime_pm, wakeref)
>  		__guc_context_sched_disable(guc, ce, guc_id);
>  
> -	return &ce->guc_blocked;
> +	return &ce->guc_state.blocked_fence;
>  }
>  
>  static void guc_context_unblock(struct intel_context *ce)
> -- 
> 2.32.0
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch