On 03/29/2013 10:24 AM, ning.n.jiang@xxxxxxxxx wrote:
> From: Ning Jiang <ning.n.jiang@xxxxxxxxx>
>
> Currently there are two problems when we try to stop local timer.
> First, it calls set_mode function directly so mode state is not
> updated for the clock event device. Second, it makes the device
> unused instead of shutdown.
>
> A subtle error will happen because of it. When a cpu is plugged out
> it will stop the local timer. It will call tick_nohz_idle_enter()
> in idle thread afterwards. It will cancel the sched timer and try
> to reprogram the next event. This is wrong since the local timer
> is supposed to be stopped.
>
> The right way to stop the local timer is to shutdown it by calling
> clockevents_set_mode(). Thus when we try to reprogram the clock
> event device, it will return directly without doing anything since
> the clock mode is CLOCK_EVT_MODE_SHUTDOWN.
>
> Signed-off-by: Ning Jiang <ning.n.jiang@xxxxxxxxx>
> ---
> arch/arm/kernel/smp_twd.c | 2 +-
> arch/arm/mach-exynos/mct.c | 2 +-
> arch/arm/mach-msm/timer.c | 2 +-
> drivers/clocksource/arm_arch_timer.c | 2 +-
> drivers/clocksource/time-armada-370-xp.c | 2 +-
> 5 files changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/arch/arm/kernel/smp_twd.c b/arch/arm/kernel/smp_twd.c
> index 3f25650..c1d4ab4 100644
> --- a/arch/arm/kernel/smp_twd.c
> +++ b/arch/arm/kernel/smp_twd.c
> @@ -92,7 +92,7 @@ static int twd_timer_ack(void)
>
> static void twd_timer_stop(struct clock_event_device *clk)
> {
> - twd_set_mode(CLOCK_EVT_MODE_UNUSED, clk);
> + clockevents_set_mode(clk, CLOCK_EVT_MODE_SHUTDOWN);
> disable_percpu_irq(clk->irq);
Wouldn't be clockevents_shutdown more adequate here ? The next event
will be also set.
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