[Intel-gfx] [PATCH 05/22] drm/i915: Lock the gem_context->active_list while dropping the link

[Tvrtko Ursulin]

On 18/03/2019 09:51, Chris Wilson wrote:
> On unpinning the intel_context, we remove it from the active list
> inside the GEM context. This list is supposed to be guarded by the GEM
> context mutex, so remember to take it!

Fixes: ?

> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> ---
>   drivers/gpu/drm/i915/intel_context.c         | 15 +++++++++++----
>   drivers/gpu/drm/i915/intel_lrc.c             |  3 ---
>   drivers/gpu/drm/i915/intel_ringbuffer.c      |  3 ---
>   drivers/gpu/drm/i915/selftests/mock_engine.c |  2 --
>   4 files changed, 11 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_context.c b/drivers/gpu/drm/i915/intel_context.c
> index 5a16c9bb2778..0ab894a058f6 100644
> --- a/drivers/gpu/drm/i915/intel_context.c
> +++ b/drivers/gpu/drm/i915/intel_context.c
> @@ -165,13 +165,13 @@ intel_context_pin(struct i915_gem_context *ctx,
>   		if (err)
>   			goto err;
>   
> +		i915_gem_context_get(ctx);
> +		GEM_BUG_ON(ce->gem_context != ctx);
> +
>   		mutex_lock(&ctx->mutex);
>   		list_add(&ce->active_link, &ctx->active_engines);
>   		mutex_unlock(&ctx->mutex);
>   
> -		i915_gem_context_get(ctx);
> -		GEM_BUG_ON(ce->gem_context != ctx);
> -
>   		smp_mb__before_atomic(); /* flush pin before it is visible */
>   	}
>   
> @@ -194,9 +194,16 @@ void intel_context_unpin(struct intel_context *ce)
>   	/* We may be called from inside intel_context_pin() to evict another */
>   	mutex_lock_nested(&ce->pin_mutex, SINGLE_DEPTH_NESTING);

Hm is the nested annotation and comment correct? Looking at it now, the 
allocations happen outside pin_mutex.

Regards,

Tvrtko

>   
> -	if (likely(atomic_dec_and_test(&ce->pin_count)))
> +	if (likely(atomic_dec_and_test(&ce->pin_count))) {
>   		ce->ops->unpin(ce);
>   
> +		mutex_lock(&ce->gem_context->mutex);
> +		list_del(&ce->active_link);
> +		mutex_unlock(&ce->gem_context->mutex);
> +
> +		i915_gem_context_put(ce->gem_context);
> +	}
> +
>   	mutex_unlock(&ce->pin_mutex);
>   }
>   
> diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
> index d3f1fe06d013..13f5545fc1d2 100644
> --- a/drivers/gpu/drm/i915/intel_lrc.c
> +++ b/drivers/gpu/drm/i915/intel_lrc.c
> @@ -1306,9 +1306,6 @@ static void execlists_context_unpin(struct intel_context *ce)
>   
>   	i915_gem_object_unpin_map(ce->state->obj);
>   	__context_unpin(ce->state);
> -
> -	list_del(&ce->active_link);
> -	i915_gem_context_put(ce->gem_context);
>   }
>   
>   static void
> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
> index 45a54fadc482..6d60bc258feb 100644
> --- a/drivers/gpu/drm/i915/intel_ringbuffer.c
> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
> @@ -1415,9 +1415,6 @@ static void ring_context_unpin(struct intel_context *ce)
>   {
>   	__context_unpin_ppgtt(ce->gem_context);
>   	__context_unpin(ce);
> -
> -	list_del(&ce->active_link);
> -	i915_gem_context_put(ce->gem_context);
>   }
>   
>   static struct i915_vma *
> diff --git a/drivers/gpu/drm/i915/selftests/mock_engine.c b/drivers/gpu/drm/i915/selftests/mock_engine.c
> index 881450c694e9..7641b74ada98 100644
> --- a/drivers/gpu/drm/i915/selftests/mock_engine.c
> +++ b/drivers/gpu/drm/i915/selftests/mock_engine.c
> @@ -126,8 +126,6 @@ static void hw_delay_complete(struct timer_list *t)
>   static void mock_context_unpin(struct intel_context *ce)
>   {
>   	mock_timeline_unpin(ce->ring->timeline);
> -	list_del(&ce->active_link);
> -	i915_gem_context_put(ce->gem_context);
>   }
>   
>   static void mock_context_destroy(struct intel_context *ce)
>