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

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Message-ID: <20160322224557.GG6356@twins.programming.kicks-ass.net>
Date:	Tue, 22 Mar 2016 23:45:57 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	Chris Metcalf <cmetcalf@...lanox.com>,
	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 Tue, Mar 22, 2016 at 11:31:11PM +0100, Rafael J. Wysocki wrote:

> > 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?

I argued against it; when you're suspended the NMI watchdog is stopped
too. Then again, you've more experience debugging that thing, so if
you think its useful its not much effort adding it.

> And analogous stuff in processor_idle.c for that matter?
> 
> acpi_idle_enter()/acpi_idle_enter_freeze() plus stuff called by those?

Ah, I only tagged acpi_processor_ffh_cstate_enter() because I went from
mwait_idle_with_hints(), I suppose acpi_safe_halt() and
acpi_idle_do_entry() itself for the INB method should cover it?

(This being one of the reasons I asked Chris to Cc you; you know this
stuff far better than I do)


---
 drivers/acpi/processor_idle.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
index 175c86bee3a9..d5b11fff9e88 100644
--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -111,7 +111,7 @@ static const struct dmi_system_id processor_power_dmi_table[] = {
  * Callers should disable interrupts before the call and enable
  * interrupts after return.
  */
-static void acpi_safe_halt(void)
+__cpuidle static void acpi_safe_halt(void)
 {
 	if (!tif_need_resched()) {
 		safe_halt();
@@ -680,7 +680,7 @@ static int acpi_idle_bm_check(void)
  *
  * Caller disables interrupt before call and enables interrupt after return.
  */
-static void acpi_idle_do_entry(struct acpi_processor_cx *cx)
+__cpuidle static void acpi_idle_do_entry(struct acpi_processor_cx *cx)
 {
 	if (cx->entry_method == ACPI_CSTATE_FFH) {
 		/* Call into architectural FFH based C-state */