[Intel-gfx] [PATCH] drm/i915/gt: Check we are the Ironlake IPS provider before deregistering

[Chris Wilson]

Check that we own the global pointer before deregistering.

Reported-by: Venkata Sandeep Dhanalakota <venkata.s.dhanalakota at intel.com>
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Venkata Sandeep Dhanalakota <venkata.s.dhanalakota at intel.com>
Cc: Andi Shyti <andi.shyti at intel.com>
---
 drivers/gpu/drm/i915/gt/intel_rps.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_rps.c b/drivers/gpu/drm/i915/gt/intel_rps.c
index 08a38a3b90b0..fd01e4100fc1 100644
--- a/drivers/gpu/drm/i915/gt/intel_rps.c
+++ b/drivers/gpu/drm/i915/gt/intel_rps.c
@@ -1715,6 +1715,7 @@ void intel_rps_driver_register(struct intel_rps *rps)
 	 * set up, to avoid intel-ips sneaking in and reading bogus values.
 	 */
 	if (IS_GEN(gt->i915, 5)) {
+		GEM_BUG_ON(ips_mchdev);
 		rcu_assign_pointer(ips_mchdev, gt->i915);
 		ips_ping_for_i915_load();
 	}
@@ -1722,7 +1723,8 @@ void intel_rps_driver_register(struct intel_rps *rps)
 
 void intel_rps_driver_unregister(struct intel_rps *rps)
 {
-	rcu_assign_pointer(ips_mchdev, NULL);
+	if (ips_mchdev == rps_to_i915(rps))
+		rcu_assign_pointer(ips_mchdev, NULL);
 }
 
 static struct drm_i915_private *mchdev_get(void)
-- 
2.24.0