linux-kernel - Re: [lkp-robot] [sched/core] 1c3c5eab17: BUG:using_smp_processor_id()in

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Date:   Wed, 24 May 2017 10:04:20 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Peter Zijlstra <peterz@...radead.org>
cc:     kernel test robot <xiaolong.ye@...el.com>,
        Ingo Molnar <mingo@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "H. Peter Anvin" <hpa@...or.com>, tipbuild@...or.com, lkp@...org
Subject: Re: [lkp-robot] [sched/core] 1c3c5eab17:
 BUG:using_smp_processor_id()in_preemptible

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) <peterz@...radead.org>

Reviewed-by: Thomas Gleixner <tglx@...utronix.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,
>