On ma, 2016-07-25 at 08:44 +0100, Chris Wilson wrote:
> Since intel_engine_enable_signaling() is now only called via
> fence_enable_sw_signaling(), we can rely on it to provide serialisation
> and run-once for us and so make ourselves slightly simpler.
>
Originally left this patch for Tvrtko, not remembering he's traveling.
assert_spin_locked() should make this enough robust that it'll still do
what it did perviously.
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
Regards, Joonas
> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/i915/intel_breadcrumbs.c | 13 ++++---------
> 1 file changed, 4 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_breadcrumbs.c b/drivers/gpu/drm/i915/intel_breadcrumbs.c
> index d893ccdd62ac..90867446f1a5 100644
> --- a/drivers/gpu/drm/i915/intel_breadcrumbs.c
> +++ b/drivers/gpu/drm/i915/intel_breadcrumbs.c
> @@ -480,19 +480,15 @@ void intel_engine_enable_signaling(struct drm_i915_gem_request *request)
> struct rb_node *parent, **p;
> bool first, wakeup;
>
> - if (unlikely(READ_ONCE(request->signaling.wait.tsk)))
> - return;
> -
> - spin_lock(&b->lock);
> - if (unlikely(request->signaling.wait.tsk)) {
> - wakeup = false;
> - goto unlock;
> - }
> + /* locked by fence_enable_sw_signaling() */
> + assert_spin_locked(&request->lock);
>
> request->signaling.wait.tsk = b->signaler;
> request->signaling.wait.seqno = request->fence.seqno;
> i915_gem_request_get(request);
>
> + spin_lock(&b->lock);
> +
> /* First add ourselves into the list of waiters, but register our
> * bottom-half as the signaller thread. As per usual, only the oldest
> * waiter (not just signaller) is tasked as the bottom-half waking
> @@ -525,7 +521,6 @@ void intel_engine_enable_signaling(struct drm_i915_gem_request *request)
> if (first)
> smp_store_mb(b->first_signal, request);
>
> -unlock:
> spin_unlock(&b->lock);
>
> if (wakeup)
--
Joonas Lahtinen
Open Source Technology Center
Intel Corporation
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