linux-kernel - Re: [PATCH v2 4/4] nmi_backtrace: generate one-line reports for idle cpus

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Message-ID: <20160321154201.GA6344@twins.programming.kicks-ass.net>
Date:	Mon, 21 Mar 2016 16:42:01 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Chris Metcalf <cmetcalf@...lanox.com>
Cc:	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 v2 4/4] nmi_backtrace: generate one-line reports for idle
 cpus

On Wed, Mar 16, 2016 at 01:02:13PM -0400, Chris Metcalf wrote:
> diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
> index 9f7c21c22477..d569ae7fde37 100644
> --- a/arch/x86/kernel/process.c
> +++ b/arch/x86/kernel/process.c
> @@ -298,7 +298,7 @@ void arch_cpu_idle(void)
>  /*
>   * We use this if we don't have any better idle routine..
>   */
> -void default_idle(void)
> +void __cpuidle default_idle(void)
>  {
>  	trace_cpu_idle_rcuidle(1, smp_processor_id());
>  	safe_halt();
> @@ -413,7 +413,7 @@ static int prefer_mwait_c1_over_halt(const struct cpuinfo_x86 *c)
>   * with interrupts enabled and no flags, which is backwards compatible with the
>   * original MWAIT implementation.
>   */
> -static void mwait_idle(void)
> +static __cpuidle void mwait_idle(void)
>  {
>  	if (!current_set_polling_and_test()) {
>  		trace_cpu_idle_rcuidle(1, smp_processor_id());

The most common idle function for x86 is: mwait_idle_with_hints(),
trouble is, its an inline, so I'm not sure adding __cpuidle to it does
anything.

I've yet to find the magic objdump incantation to check. Or rather
objdump -h doesn't appear to list .cpuidle.text at all :/

I'm probably doing something silly...