time: don't touch an offlined CPU's ts->tick_stopped in tick_cancel_sched_timer()

Silences WARN_ONs in rcu_enter_nohz() and rcu_exit_nohz(), which appeared
before caused by (repeated) calls to:
        $ echo 0 > /sys/devices/system/cpu/cpu1/online
        $ echo 1 > /sys/devices/system/cpu/cpu1/online

Signed-off-by: Karsten Wiese <fzu@wemgehoertderstaat.de>
Cc: johnstul@us.ibm.com
Cc: Rafael Wysocki <rjw@sisk.pl>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ingo Molnar <mingo@elte.hu>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 2968298f8f364923010c440fe68f6e02d2f32e2a..686da821d376b01dd21d379bfd8baf39d6b106f1 100644 (file)
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -640,7 +640,7 @@ void tick_cancel_sched_timer(int cpu)
 
        if (ts->sched_timer.base)
                hrtimer_cancel(&ts->sched_timer);
-       ts->tick_stopped = 0;
+
        ts->nohz_mode = NOHZ_MODE_INACTIVE;
 }
 #endif /* HIGH_RES_TIMERS */