* counters if NULL.
*
* Return the cumulative idle time (since boot) for a given
- * CPU, in microseconds.
+ * CPU, in microseconds. Note this is partially broken due to
+ * the counter of iowait tasks that can be remotely updated without
+ * any synchronization. Therefore it is possible to observe backward
+ * values within two consecutive reads.
*
* This time is measured via accounting rather than sampling,
* and is as accurate as ktime_get() is.
* counters if NULL.
*
* Return the cumulative iowait time (since boot) for a given
- * CPU, in microseconds.
+ * CPU, in microseconds. Note this is partially broken due to
+ * the counter of iowait tasks that can be remotely updated without
+ * any synchronization. Therefore it is possible to observe backward
+ * values within two consecutive reads.
*
* This time is measured via accounting rather than sampling,
* and is as accurate as ktime_get() is.