linux/kernel/time
Thomas Gleixner 6ff7041dbf hrtimer: Fix migration expiry check
The timer migration expiry check should prevent the migration of a
timer to another CPU when the timer expires before the next event is
scheduled on the other CPU. Migrating the timer might delay it because
we can not reprogram the clock event device on the other CPU. But the
code implementing that check has two flaws:

- for !HIGHRES the check compares the expiry value with the clock
  events device expiry value which is wrong for CLOCK_REALTIME based
  timers.

- the check is racy. It holds the hrtimer base lock of the target CPU,
  but the clock event device expiry value can be modified
  nevertheless, e.g. by an timer interrupt firing.

The !HIGHRES case is easy to fix as we can enqueue the timer on the
cpu which was selected by the load balancer. It runs the idle
balancing code once per jiffy anyway. So the maximum delay for the
timer is the same as when we keep the tick on the current cpu going.

In the HIGHRES case we can get the next expiry value from the hrtimer
cpu_base of the target CPU and serialize the update with the cpu_base
lock. This moves the lock section in hrtimer_interrupt() so we can set
next_event to KTIME_MAX while we are handling the expired timers and
set it to the next expiry value after we handled the timers under the
base lock. While the expired timers are processed timer migration is
blocked because the expiry time of the timer is always <= KTIME_MAX.

Also remove the now useless clockevents_get_next_event() function.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2009-07-10 17:32:55 +02:00
..
clockevents.c hrtimer: Fix migration expiry check 2009-07-10 17:32:55 +02:00
clocksource.c clocksource: prevent selection of low resolution clocksourse also for nohz=on 2009-06-13 12:00:26 +02:00
jiffies.c clocksource: pass clocksource to read() callback 2009-04-21 13:41:47 -07:00
Kconfig Kconfig: eliminate "def_bool n" constructs 2008-10-16 11:21:31 -07:00
Makefile timecompare: generic infrastructure to map between two time bases 2009-02-15 22:43:32 -08:00
ntp.c time: ntp: fix bug in ntp_update_offset() & do_adjtimex(), fix 2009-02-26 19:39:47 +01:00
tick-broadcast.c clockevents: tick_broadcast_device can become static 2009-05-02 10:31:14 +02:00
tick-common.c clockevents: prevent endless loop in tick_handle_periodic() 2009-05-02 10:22:27 +02:00
tick-internal.h NOHZ: restart tick device from irq_enter() 2008-10-17 18:13:38 +02:00
tick-oneshot.c clocksource: prevent selection of low resolution clocksourse also for nohz=on 2009-06-13 12:00:26 +02:00
tick-sched.c Merge branch 'timers-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2009-06-20 10:51:44 -07:00
timecompare.c timecompare: generic infrastructure to map between two time bases 2009-02-15 22:43:32 -08:00
timekeeping.c Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6 2009-06-11 09:01:14 +03:00
timer_list.c Merge branch 'timers/range-hrtimers' into v28-range-hrtimers-for-linus-v2 2008-10-22 09:48:06 +02:00
timer_stats.c timer stats: Optimize by adding quick check to avoid function calls 2009-06-24 11:15:09 +02:00