[Intel-gfx] [PATCH] drm/i915: Repeat flush of idle work during suspend

[Chris Wilson]

The idle work handler is self-arming - if it detects that it needs to
run again it will queue itself from its work handler. Take greater care
when trying to drain the idle work, and double check that it is flushed.

The free worker has a similar issue where it is armed by an RCU task
which may be running concurrently with us.

This should hopefully help with the sporadic WARN_ON(dev_priv->gt.awake)
from i915_gem_suspend.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/i915_gem.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 9b308af89ada..7a48b264fd18 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -4245,8 +4245,12 @@ int i915_gem_suspend(struct drm_i915_private *dev_priv)
 
 	cancel_delayed_work_sync(&dev_priv->gpu_error.hangcheck_work);
 	cancel_delayed_work_sync(&dev_priv->gt.retire_work);
-	flush_delayed_work(&dev_priv->gt.idle_work);
-	flush_work(&dev_priv->mm.free_work);
+	while (flush_delayed_work(&dev_priv->gt.idle_work))
+		;
+
+	rcu_barrier();
+	while (flush_work(&dev_priv->mm.free_work))
+		rcu_barrier();
 
 	/* Assert that we sucessfully flushed all the work and
 	 * reset the GPU back to its idle, low power state.
-- 
2.11.0