[Intel-gfx] [PATCH 2/3] drm/i915: Flush the tasklet when checking for idle

[Chris Wilson]

In order to reduce latency when checking for idle we kick the tasklet
directly. Sometimes this is not enough as it is queued on another cpu
and so to improve the accuracy of this idle-check (and so to reduce
latency overall by avoiding another pass, or worse declaring a timeout!)
wait for the tasklet to complete.

References: https://bugs.freedesktop.org/show_bug.cgi?id=107916
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
Cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>
Cc: Michel Thierry <michel.thierry at intel.com>
---
 drivers/gpu/drm/i915/intel_engine_cs.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_engine_cs.c b/drivers/gpu/drm/i915/intel_engine_cs.c
index 10cd051ba29e..217ed3ee1cab 100644
--- a/drivers/gpu/drm/i915/intel_engine_cs.c
+++ b/drivers/gpu/drm/i915/intel_engine_cs.c
@@ -990,6 +990,9 @@ bool intel_engine_is_idle(struct intel_engine_cs *engine)
 		}
 		local_bh_enable();
 
+		/* Otherwise flush the tasklet if it was on another cpu */
+		tasklet_unlock_wait(t);
+
 		if (READ_ONCE(engine->execlists.active))
 			return false;
 	}
-- 
2.19.0