linux-kernel - Re: [PATCH] ARM: arch_timer: Silence debug preempt warnings

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Message-ID: <515E5CFC.4090900@codeaurora.org>
Date:	Thu, 04 Apr 2013 22:11:24 -0700
From:	Stephen Boyd <sboyd@...eaurora.org>
To:	John Stultz <john.stultz@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>
CC:	linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	Mark Rutland <mark.rutland@....com>,
	Marc Zyngier <Marc.Zyngier@....com>
Subject: Re: [PATCH] ARM: arch_timer: Silence debug preempt warnings

On 4/2/2013 1:31 PM, Stephen Boyd wrote:
> Hot-plugging with CONFIG_DEBUG_PREEMPT=y on a device with arm
> architected timers causes a slew of "using smp_processor_id() in
> preemptible" warnings:
>
>   BUG: using smp_processor_id() in preemptible [00000000] code: sh/111
>   caller is arch_timer_cpu_notify+0x14/0xc8
>
> This happens because sometimes the cpu notifier, arch_timer_cpu_notify(),
> is called in preemptible context but we use this_cpu_ptr()
> to retrieve the clockevent unconditionally. We're only going to
> actually use the pointer in non-preemptible context though,
> so use __this_cpu_ptr() instead to avoid the preemptible checks
> and silence the warning.
>
> Cc: Mark Rutland <mark.rutland@....com>
> Cc: Marc Zyngier <Marc.Zyngier@....com>
> Signed-off-by: Stephen Boyd <sboyd@...eaurora.org>
> ---

Anyone else seeing this one?

>  drivers/clocksource/arm_arch_timer.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
> index d7ad425..5928c29 100644
> --- a/drivers/clocksource/arm_arch_timer.c
> +++ b/drivers/clocksource/arm_arch_timer.c
> @@ -248,7 +248,7 @@ static void __cpuinit arch_timer_stop(struct clock_event_device *clk)
>  static int __cpuinit arch_timer_cpu_notify(struct notifier_block *self,
>  					   unsigned long action, void *hcpu)
>  {
> -	struct clock_event_device *evt = this_cpu_ptr(arch_timer_evt);
> +	struct clock_event_device *evt = __this_cpu_ptr(arch_timer_evt);
>  
>  	switch (action & ~CPU_TASKS_FROZEN) {
>  	case CPU_STARTING:

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