linux-kernel - Re: [PATCH v2 1/2] time/sched_clock: Disable interrupts in sched_clock

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Date:   Thu, 9 Jan 2020 12:55:47 +0100
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Paul Cercueil <paul@...pouillou.net>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     od@...c.me, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] time/sched_clock: Disable interrupts in
 sched_clock_register

On 07/01/2020 02:06, Paul Cercueil wrote:
> Instead of issueing a warning if sched_clock_register is called from a
> context where IRQs are enabled, the code now ensures that IRQs are
> indeed disabled.
> 
> Signed-off-by: Paul Cercueil <paul@...pouillou.net>

Acked-by: Daniel Lezcano <daniel.lezcano@...aro.org>


> ---
> 
> Notes:
>     v2: New patch
> 
>  kernel/time/sched_clock.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/time/sched_clock.c b/kernel/time/sched_clock.c
> index dbd69052eaa6..e4332e3e2d56 100644
> --- a/kernel/time/sched_clock.c
> +++ b/kernel/time/sched_clock.c
> @@ -169,14 +169,15 @@ sched_clock_register(u64 (*read)(void), int bits, unsigned long rate)
>  {
>  	u64 res, wrap, new_mask, new_epoch, cyc, ns;
>  	u32 new_mult, new_shift;
> -	unsigned long r;
> +	unsigned long r, flags;
>  	char r_unit;
>  	struct clock_read_data rd;
>  
>  	if (cd.rate > rate)
>  		return;
>  
> -	WARN_ON(!irqs_disabled());
> +	/* Cannot register a sched_clock with interrupts on */
> +	local_irq_save(flags);
>  
>  	/* Calculate the mult/shift to convert counter ticks to ns. */
>  	clocks_calc_mult_shift(&new_mult, &new_shift, rate, NSEC_PER_SEC, 3600);
> @@ -233,6 +234,8 @@ sched_clock_register(u64 (*read)(void), int bits, unsigned long rate)
>  	if (irqtime > 0 || (irqtime == -1 && rate >= 1000000))
>  		enable_sched_clock_irqtime();
>  
> +	local_irq_restore(flags);
> +
>  	pr_debug("Registered %pS as sched_clock source\n", read);
>  }
>  
> 


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