drm/i915: Fix incorrect assert about pending power domain async-put work

It's possible that an already dequeued put_async_work() will release the
reference (*) that was put asynchronously after the dequeue happened.
This leaves an async-put work pending, without any reference to release.
A subsequent async-put may trigger the

drm_WARN_ON(!queue_delayed_work(&power_domains->async_put_work));

warn due to async_put_work() still pending. To avoid the warn, cancel
the pending async_put_work() when releasing the reference at (*) above.

Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/3421
Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/2289
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Anshuman Gupta <anshuman.gupta@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210526143729.2563672-2-imre.deak@intel.com

diff --git a/drivers/gpu/drm/i915/display/intel_display_power.c b/drivers/gpu/drm/i915/display/intel_display_power.c
index c8471d70cb8e01457f21c72f264b178259bb1504..2ece50323c6dcf012091ecdf1a4521908ff1a56c 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_display_power.c
+++ b/drivers/gpu/drm/i915/display/intel_display_power.c
@@ -2263,6 +2263,12 @@ intel_display_power_put_async_work(struct work_struct *work)
                        fetch_and_zero(&power_domains->async_put_domains[1]);
                queue_async_put_domains_work(power_domains,
                                             fetch_and_zero(&new_work_wakeref));
+       } else {
+               /*
+                * Cancel the work that got queued after this one got dequeued,
+                * since here we released the corresponding async-put reference.
+                */
+               cancel_delayed_work(&power_domains->async_put_work);
        }
 
 out_verify: