qcacld-3.0: Wait for external threads to complete before con mode switch

Interface up runs in normal mode ([email protected]) and it gets
preempted by the con_mode change handler when Monitor mode is
invoked via user. Then again when the normal mode gets scheduled
after the completion of Monitor mode, it tries to access contents
freed during the con_mode change.

The __con_mode_handler is made to wait for the external
threads to complete before making the con mode switch

Change-Id: I245b6b6f855e119a11422677da161a43c1184069
CRs-fixed: 2147499

core/hdd/src/wlan_hdd_main.c

@@ -11836,6 +11836,9 @@ static int __con_mode_handler(const char *kmessage, struct kernel_param *kp,
 		goto reset_flags;
 	}
 
+	if (!cds_wait_for_external_threads_completion(__func__))
+		hdd_warn("Waiting for monitor mode: External threads are active");
+
 	/* ensure adapters are stopped */
 	hdd_stop_present_mode(hdd_ctx, curr_mode);