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Subject[PATCH] nohz: fix wrong event handler after online an offlined cpu
On the tickless system(CONFIG_NO_HZ=y and CONFIG_HIGH_RES_TIMERS=n), after I
made an offlined cpu online, I found this cpu's event handler was
tick_handle_periodic, not tick_nohz_handler.

After debuging, I found this bug was caused by the wrong tick mode.
the tick mode is not changed to NOHZ_MODE_INACTIVE when the cpu is offline.

This patch fixes this bug.

Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>

---
include/linux/tick.h | 5 ++++-
kernel/time/tick-sched.c | 6 +++++-
2 files changed, 9 insertions(+), 2 deletions(-)
diff --git a/include/linux/tick.h b/include/linux/tick.h
index d3c0269..8cf8cfe 100644
--- a/include/linux/tick.h
+++ b/include/linux/tick.h
@@ -74,10 +74,13 @@ extern struct tick_device *tick_get_device(int cpu);
extern int tick_init_highres(void);
extern int tick_program_event(ktime_t expires, int force);
extern void tick_setup_sched_timer(void);
+# endif
+
+# if defined CONFIG_NO_HZ || defined CONFIG_HIGH_RES_TIMERS
extern void tick_cancel_sched_timer(int cpu);
# else
static inline void tick_cancel_sched_timer(int cpu) { }
-# endif /* HIGHRES */
+# endif

# ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
extern struct tick_device *tick_get_broadcast_device(void);
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 825b4c0..661a392 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -645,17 +645,21 @@ void tick_setup_sched_timer(void)
ts->nohz_mode = NOHZ_MODE_HIGHRES;
#endif
}
+#endif /* HIGH_RES_TIMERS */

+#if defined CONFIG_NO_HZ || defined CONFIG_HIGH_RES_TIMERS
void tick_cancel_sched_timer(int cpu)
{
struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);

+# ifdef CONFIG_HIGH_RES_TIMERS
if (ts->sched_timer.base)
hrtimer_cancel(&ts->sched_timer);
+# endif

ts->nohz_mode = NOHZ_MODE_INACTIVE;
}
-#endif /* HIGH_RES_TIMERS */
+#endif

/**
* Async notification about clocksource changes
--
1.5.4.rc3


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