[PATCH 3/8] cputime: introduce account_idle_and_iowait

[Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>]

The current account_idle_time() cannot process mixed cputime which
contain both of idle cputime and iowait cputime.

So introduce new account_idle_and_iowait() to do paranoid work.
Following patches will add users of this new function.

Not-Tested-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
---
 kernel/sched/cputime.c |   24 +++++++++++++++++++++++-
 1 files changed, 23 insertions(+), 1 deletions(-)

diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
index a028604..283e011 100644
--- a/kernel/sched/cputime.c
+++ b/kernel/sched/cputime.c
@@ -240,14 +240,36 @@ void account_steal_time(cputime_t cputime)
 }
 
 /*
+ * Account for idle and iowait time in a dulation.
+ * @idle_enter: time stamp at idle entry
+ * @iowait_exit: time stamp when nr_iowait dropped to 0
+ * @idle_exit: time stamp at idle exit
+ */
+void account_idle_and_iowait(cputime_t idle_enter, cputime_t iowait_exit, cputime_t idle_exit)
+{
+	u64 *cpustat = kcpustat_this_cpu->cpustat;
+	struct rq *rq = this_rq();
+
+	if (rq->nr_iowait > 0 || iowait_exit > idle_exit) {
+		cpustat[CPUTIME_IOWAIT] += (__force u64) idle_exit - idle_enter;
+	} else if (iowait_exit > idle_enter) {
+		cpustat[CPUTIME_IOWAIT] += (__force u64) iowait_exit - idle_enter;
+		cpustat[CPUTIME_IDLE] += (__force u64) idle_exit - iowait_exit;
+	} else {
+		cpustat[CPUTIME_IDLE] += (__force u64) idle_exit - idle_enter;
+	}
+}
+
+/*
  * Account for idle time.
- * @cputime: the cpu time spent in idle wait
+ * @cputime: the cpu time spent in idle wait (sometimes include iowait time)
  */
 void account_idle_time(cputime_t cputime)
 {
 	u64 *cpustat = kcpustat_this_cpu->cpustat;
 	struct rq *rq = this_rq();
 
+	/* FIXME */
 	if (rq->nr_iowait > 0)
 		cpustat[CPUTIME_IOWAIT] += (__force u64) cputime;
 	else
-- 
1.7.1