[PATCH iwl-net v5 8/8] ice: Release control PF lock before RCU wait

[Sergey Temerkhanov <sergey.temerkhanov@intel.com>]

Clear ctrl_pf while holding ctrl_pf_lock for write, but release the
rwsem before waiting for pre-existing RCU readers. The published NULL
already prevents new readers from acquiring the retiring PF, so holding
the writer lock through synchronize_rcu() only stalls sleepable users.

Signed-off-by: Sergey Temerkhanov <sergey.temerkhanov@intel.com>
Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
---
 drivers/net/ethernet/intel/ice/ice_ptp.c | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/drivers/net/ethernet/intel/ice/ice_ptp.c b/drivers/net/ethernet/intel/ice/ice_ptp.c
index 3ed37bbae161..24d4ab2197c3 100644
--- a/drivers/net/ethernet/intel/ice/ice_ptp.c
+++ b/drivers/net/ethernet/intel/ice/ice_ptp.c
@@ -3302,16 +3302,21 @@ static void ice_ptp_setup_adapter(struct ice_pf *pf)
 
 static void ice_ptp_cleanup_adapter(struct ice_pf *pf)
 {
-	guard(rwsem_write)(&pf->adapter->ctrl_pf_lock);
+	bool synchronize = false;
 
-	/* Zero out adapter->ctrl_pf pointer when the ctrl_pf itself
-	 * is being removed to prevent any secondary PFs from accessing
-	 * it after it is deleted.
-	 */
-	if (ice_get_ctrl_pf(pf) == pf) {
-		rcu_assign_pointer(pf->adapter->ctrl_pf, NULL);
-		synchronize_rcu();
+	scoped_guard(rwsem_write, &pf->adapter->ctrl_pf_lock) {
+		/* Zero out adapter->ctrl_pf pointer when the ctrl_pf itself
+		 * is being removed to prevent any secondary PFs from accessing
+		 * it after it is deleted.
+		 */
+		if (ice_get_ctrl_pf(pf) == pf) {
+			rcu_assign_pointer(pf->adapter->ctrl_pf, NULL);
+			synchronize = true;
+		}
 	}
+
+	if (synchronize)
+		synchronize_rcu();
 }
 
 static int ice_ptp_setup_pf(struct ice_pf *pf)
-- 
2.53.0