[Intel-gfx] [PATCH v2] drm/i915: Keep engine alive as we retire the context

[Chris Wilson]

Quoting Chris Wilson (2019-06-17 10:32:27)
> Though we pin the context first before taking the pm wakeref, during
> retire we need to unpin before dropping the pm wakeref (breaking the
> "natural" onion). During the unpin, we may need to attach a cleanup
> operation on to the engine wakeref, ergo we want to keep the engine
> awake until after the unpin.
> 
> v2: Push the engine wakeref into the barrier so we keep the onion unwind
> ordering in the request itself
> 
> Fixes: ce476c80b8bf ("drm/i915: Keep contexts pinned until after the next kernel context switch")
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>
> ---
>  drivers/gpu/drm/i915/i915_active.c | 23 +++++++++++++++++++++--
>  1 file changed, 21 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_active.c b/drivers/gpu/drm/i915/i915_active.c
> index 2d019ac6db20..a803ad42075d 100644
> --- a/drivers/gpu/drm/i915/i915_active.c
> +++ b/drivers/gpu/drm/i915/i915_active.c
> @@ -4,6 +4,8 @@
>   * Copyright © 2019 Intel Corporation
>   */
>  
> +#include "gt/intel_engine_pm.h"
> +
>  #include "i915_drv.h"
>  #include "i915_active.h"
>  #include "i915_globals.h"
> @@ -268,8 +270,9 @@ int i915_active_acquire_preallocate_barrier(struct i915_active *ref,
>                                             struct intel_engine_cs *engine)
>  {
>         struct drm_i915_private *i915 = engine->i915;
> +       struct llist_node *pos, *next;
>         unsigned long tmp;
> -       int err = 0;
> +       int err;
>  
>         GEM_BUG_ON(!engine->mask);
>         for_each_engine_masked(engine, i915, engine->mask, tmp) {
> @@ -278,8 +281,9 @@ int i915_active_acquire_preallocate_barrier(struct i915_active *ref,
>  
>                 node = kmem_cache_alloc(global.slab_cache, GFP_KERNEL);
>                 if (unlikely(!node)) {
> +                       intel_engine_pm_put(engine);

Oh no, didn't remove after reordering.
-Chris