linux-kernel - Re: [PATCH v3 4/4] nmi_backtrace: generate one-line reports for idle cpus

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Message-ID: <54039485.X1biSGXPBa@vostro.rjw.lan>
Date:	Tue, 22 Mar 2016 23:31:11 +0100
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Chris Metcalf <cmetcalf@...lanox.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Russell King <linux@....linux.org.uk>,
	Thomas Gleixner <tglx@...utronix.de>,
	Aaron Tomlin <atomlin@...hat.com>,
	Ingo Molnar <mingo@...hat.com>, Andrew Morton <akpm@...l.org>,
	Daniel Thompson <daniel.thompson@...aro.org>, x86@...nel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-arch@...r.kernel.org
Subject: Re: [PATCH v3 4/4] nmi_backtrace: generate one-line reports for idle cpus

On Tuesday, March 22, 2016 01:19:39 PM Chris Metcalf wrote:
> When doing an nmi backtrace of many cores, most of which are idle,
> the output is a little overwhelming and very uninformative.  Suppress
> messages for cpus that are idling when they are interrupted and just
> emit one line, "NMI backtrace for N skipped: idling at pc 0xNNN".
> 
> We do this by grouping all the cpuidle code together into a new
> .cpuidle.text section, and then checking the address of the
> interrupted PC to see if it lies within that section.
> 
> This commit suitably tags x86, arm64, and tile idle routines,
> and only adds in the minimal framework for other architectures.
> 
> Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> Tested-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> Signed-off-by: Chris Metcalf <cmetcalf@...lanox.com>
> ---

[cut]

> diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
> index cd4510a63375..924554f920fb 100644
> --- a/drivers/idle/intel_idle.c
> +++ b/drivers/idle/intel_idle.c
> @@ -725,8 +725,8 @@ static struct cpuidle_state avn_cstates[] = {
>   *
>   * Must be called under local_irq_disable().
>   */
> -static int intel_idle(struct cpuidle_device *dev,
> -		struct cpuidle_driver *drv, int index)
> +static __cpuidle int intel_idle(struct cpuidle_device *dev,
> +				struct cpuidle_driver *drv, int index)
>  {
>  	unsigned long ecx = 1; /* break on interrupt flag */
>  	struct cpuidle_state *state = &drv->states[index];

Well, what about intel_idle_freeze()?  Or do we not care?

And analogous stuff in processor_idle.c for that matter?

acpi_idle_enter()/acpi_idle_enter_freeze() plus stuff called by those?

Thanks,
Rafael