If the fence context has notifies enabled, each of the fences'
FENCE_FLAG_SIGNALED_BIT will be updated from the interrupt. We can rely
on this status for reporting the current fence_is_signaled() and so
avoid an expensive uncached read.
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Ben Skeggs <bskeggs at redhat.com>
Cc: dri-devel at lists.freedesktop.org
Cc: nouveau at lists.freedesktop.org
---
drivers/gpu/drm/nouveau/nouveau_fence.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/drivers/gpu/drm/nouveau/nouveau_fence.c
b/drivers/gpu/drm/nouveau/nouveau_fence.c
index 4bb9ab892ae1..7daed5c33043 100644
--- a/drivers/gpu/drm/nouveau/nouveau_fence.c
+++ b/drivers/gpu/drm/nouveau/nouveau_fence.c
@@ -510,6 +510,16 @@ static bool nouveau_fence_is_signaled(struct fence *f)
struct nouveau_channel *chan;
bool ret = false;
+ /* If the notify is already active, we can rely on
+ * FENCE_FLAG_SIGNALED_BIT being accurate and skip checking the
+ * current seqno as fctx->read() requires an expensive uncached read.
+ */
+ if (test_bit(FENCE_FLAG_USER_BITS, &fence->base.flags))
+ return false;
+
+ if (READ_ONCE(fctx->notify_ref))
+ return false;
+
rcu_read_lock();
chan = rcu_dereference(fence->channel);
if (chan)
--
2.9.3
