nohz: Track last do_timer() cpu

The previous patch which limits the sleep time to the maximum
deferment time of the time keeping clocksource has some limitations on
SMP machines: if all CPUs are idle then for all CPUs the maximum sleep
time is limited.

Solve this by keeping track of which cpu had the do_timer() duty
assigned last and limit the sleep time only for this cpu.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
LKML-Reference: <new-submission>
Cc: Jon Hunter <jon-hunter@ti.com>
Cc: John Stultz <johnstul@us.ibm.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/linux/tick.h b/include/linux/tick.h
index 8dc082194b22..d2ae79e21be3 100644
--- a/include/linux/tick.h
+++ b/include/linux/tick.h
@@ -43,6 +43,7 @@ enum tick_nohz_mode {
  * @idle_exittime:      Time when the idle state was left
  * @idle_sleeptime:     Sum of the time slept in idle with sched tick stopped
  * @sleep_length:       Duration of the current idle sleep
+ * @do_timer_lst:       CPU was the last one doing do_timer before going idle
  */
 struct tick_sched {
         struct hrtimer                  sched_timer;
@@ -64,6 +65,7 @@ struct tick_sched {
         unsigned long                   last_jiffies;
         unsigned long                   next_jiffies;
         ktime_t                         idle_expires;
+        int                             do_timer_last;
 };
 
 extern void __init tick_init(void);