[Intel-gfx] [PATCH] drm/i915: Serialise read/write of the barrier's engine

[Joonas Lahtinen]

Quoting Chris Wilson (2019-08-13 23:09:05)
> We use the request pointer inside the i915_active_node as the indicator
> of the barrier's status; we mark it as used during
> i915_request_add_active_barriers(), and search for an available barrier
> in reuse_idle_barrier(). That check must be carefully serialised to
> ensure we do use an engine for the barrier and not just a random
> pointer. (Along the other reuse path, we are fully serialised by the
> timeline->mutex.) The acquisition of the barrier itself is ordered through
> the strong memory barrier in llist_del_all().
> 
> Fixes: d8af05ff38ae ("drm/i915: Allow sharing the idle-barrier from other kernel requests")
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>

Reviewed-by: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>

Regards, Joonas