drm/i915: Reduce breadcrumb lock coverage for intel_engine_enable_signaling()
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.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/1469432687-22756-2-git-send-email-chris@chris-wilson.co.uk
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1469530913-17180-1-git-send-email-chris@chris-wilson.co.uk
diff --git a/drivers/gpu/drm/i915/intel_breadcrumbs.c b/drivers/gpu/drm/i915/intel_breadcrumbs.c
index d893ccd..9086744 100644
--- a/drivers/gpu/drm/i915/intel_breadcrumbs.c
+++ b/drivers/gpu/drm/i915/intel_breadcrumbs.c
@@ -480,19 +480,15 @@
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 @@
if (first)
smp_store_mb(b->first_signal, request);
-unlock:
spin_unlock(&b->lock);
if (wakeup)