Re: [PATCH] Revert "cpufreq: governor: Fix negative idle_time when configured with CONFIG_HZ_PERIODIC"

[Viresh Kumar]

On 21-04-16, 20:57, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> 
> Revert commit 0df35026c6a5 (cpufreq: governor: Fix negative idle_time
> when configured with CONFIG_HZ_PERIODIC) that introduced a regression
> by causing the ondemand cpufreq governor to misbehave for
> CONFIG_TICK_CPU_ACCOUNTING unset (the frequency goes up to the max at
> one point and stays there indefinitely).
> 
> The revert takes subsequent modifications of the code in question into
> account.
> 
> Fixes: 0df35026c6a5 (cpufreq: governor: Fix negative idle_time when configured with CONFIG_HZ_PERIODIC)
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=115261
> Reported-and-tested-by: Timo Valtoaho <timo.valtoaho@xxxxxxxxx>
> Cc: 4.5+ <stable@xxxxxxxxxxxxxxx> # 4.5+
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> ---
>  drivers/cpufreq/cpufreq_governor.c |    8 ++------
>  1 file changed, 2 insertions(+), 6 deletions(-)
> 
> Index: linux-pm/drivers/cpufreq/cpufreq_governor.c
> ===================================================================
> --- linux-pm.orig/drivers/cpufreq/cpufreq_governor.c
> +++ linux-pm/drivers/cpufreq/cpufreq_governor.c
> @@ -146,12 +146,8 @@ unsigned int dbs_update(struct cpufreq_p
>  		wall_time = cur_wall_time - j_cdbs->prev_cpu_wall;
>  		j_cdbs->prev_cpu_wall = cur_wall_time;
>  
> -		if (cur_idle_time <= j_cdbs->prev_cpu_idle) {
> -			idle_time = 0;
> -		} else {
> -			idle_time = cur_idle_time - j_cdbs->prev_cpu_idle;
> -			j_cdbs->prev_cpu_idle = cur_idle_time;
> -		}
> +		idle_time = cur_idle_time - j_cdbs->prev_cpu_idle;
> +		j_cdbs->prev_cpu_idle = cur_idle_time;
>  
>  		if (ignore_nice) {
>  			u64 cur_nice = kcpustat_cpu(j).cpustat[CPUTIME_NICE];

Acked-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx>

-- 
viresh