Re: [PATCH] ACPI: idle: mark_tsc_unstable() at init-time, not run-time

[Thomas Gleixner <tglx@linutronix.de>]

On Tue, 21 Apr 2009, Len Brown wrote:

> From: Len Brown <len.brown@intel.com>
> 
> The c2 and c3 idle handlers check tsc_halts_in_c()
> after every time they return from idle.  Um, when?:-)
> 
> Move this check to init-time to remove the unnecessary
> run-time overhead, and also to have the check complete before
> the first entry into the idle handler.
> 
> ff69f2bba67bd45514923aaedbf40fe351787c59
> (acpi: fix of pmtimer overflow that make Cx states time incorrect)
> replaced the hard-coded use of the PM-timer inside idle,
> with ktime_get_readl(), which possibly uses the TSC --
> so it is now especially prudent to detect a broken TSC
> before entering idle.
> 
> http://bugzilla.kernel.org/show_bug.cgi?id=13087
> 
> Signed-off-by: Len Brown <len.brown@intel.com>

Acked-by: Thomas Gleixner <tglx@linutronix.de>

> ---
>  drivers/acpi/processor_idle.c |   15 +++++----------
>  1 files changed, 5 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
> index 6fe1214..9d1f01e 100644
> --- a/drivers/acpi/processor_idle.c
> +++ b/drivers/acpi/processor_idle.c
> @@ -581,6 +581,11 @@ static int acpi_processor_power_verify(struct acpi_processor *pr)
>  	for (i = 1; i < ACPI_PROCESSOR_MAX_POWER; i++) {
>  		struct acpi_processor_cx *cx = &pr->power.states[i];
>  
> +#if defined (CONFIG_GENERIC_TIME) && defined (CONFIG_X86)
> +		/* TSC could halt in idle, so notify users */
> +		if (tsc_halts_in_c(cx->type))
> +			mark_tsc_unstable("TSC halts in idle");;
> +#endif
>  		switch (cx->type) {
>  		case ACPI_STATE_C1:
>  			cx->valid = 1;
> @@ -871,11 +876,6 @@ static int acpi_idle_enter_simple(struct cpuidle_device *dev,
>  	kt2 = ktime_get_real();
>  	idle_time =  ktime_to_us(ktime_sub(kt2, kt1));
>  
> -#if defined (CONFIG_GENERIC_TIME) && defined (CONFIG_X86)
> -	/* TSC could halt in idle, so notify users */
> -	if (tsc_halts_in_c(cx->type))
> -		mark_tsc_unstable("TSC halts in idle");;
> -#endif
>  	sleep_ticks = us_to_pm_timer_ticks(idle_time);
>  
>  	/* Tell the scheduler how much we idled: */
> @@ -989,11 +989,6 @@ static int acpi_idle_enter_bm(struct cpuidle_device *dev,
>  		spin_unlock(&c3_lock);
>  	}
>  
> -#if defined (CONFIG_GENERIC_TIME) && defined (CONFIG_X86)
> -	/* TSC could halt in idle, so notify users */
> -	if (tsc_halts_in_c(ACPI_STATE_C3))
> -		mark_tsc_unstable("TSC halts in idle");
> -#endif
>  	sleep_ticks = us_to_pm_timer_ticks(idle_time);
>  	/* Tell the scheduler how much we idled: */
>  	sched_clock_idle_wakeup_event(sleep_ticks*PM_TIMER_TICK_NS);
> -- 
> 1.6.3.rc1.18.g66996
>