drm/i915/gt: Check we are the Ironlake IPS provider before deregistering

Check that we own the global pointer before deregistering.

Reported-by: Venkata Sandeep Dhanalakota <venkata.s.dhanalakota@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Venkata Sandeep Dhanalakota <venkata.s.dhanalakota@intel.com>
Cc: Andi Shyti <andi.shyti@intel.com>
Reviewed-by: Venkata Sandeep Dhanalakota <venkata.s.dhanalakota@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191210153620.3929372-1-chris@chris-wilson.co.uk

diff --git a/drivers/gpu/drm/i915/gt/intel_rps.c b/drivers/gpu/drm/i915/gt/intel_rps.c
index 08a38a3b90b03b6217d588968db19ffdbf9111df..fd01e4100fc143a47941158dc9340e590f18d525 100644 (file)
--- 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)