On Wed, 24 May 2017, Peter Zijlstra wrote:
> Subject: sched/clock: Fix early boot preempt warning
>
> The more strict early boot preemption warnings found that
> __set_sched_clock_stable() was incorrectly assuming we'd still be
> running on a single CPU.
>
> Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org>
Reviewed-by: Thomas Gleixner <t...@linutronix.de>
> ---
> kernel/sched/clock.c | 9 ++++++++-
> 1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/sched/clock.c b/kernel/sched/clock.c
> index 1a0d389d2f2b..ca0f8fc945c6 100644
> --- a/kernel/sched/clock.c
> +++ b/kernel/sched/clock.c
> @@ -133,12 +133,19 @@ static void __scd_stamp(struct sched_clock_data *scd)
>
> static void __set_sched_clock_stable(void)
> {
> - struct sched_clock_data *scd = this_scd();
> + struct sched_clock_data *scd;
>
> /*
> + * Since we're still unstable and the tick is already running, we have
> + * to disable IRQs in order to get a consistent scd->tick* reading.
> + */
> + local_irq_disable();
> + scd = this_scd();
> + /*
> * Attempt to make the (initial) unstable->stable transition continuous.
> */
> __sched_clock_offset = (scd->tick_gtod + __gtod_offset) -
> (scd->tick_raw);
> + local_irq_enable();
>
> printk(KERN_INFO "sched_clock: Marking stable (%lld, %lld)->(%lld,
> %lld)\n",
> scd->tick_gtod, __gtod_offset,
>
