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SubjectRe: [PATCH 2/2] cpuidle / menu: Return error code if there are no suitable states
On 04/30/2014 01:16 AM, Rafael J. Wysocki wrote:
> On Tuesday, April 29, 2014 01:28:03 AM Rafael J. Wysocki wrote:
>> On Monday, April 28, 2014 01:14:32 PM Daniel Lezcano wrote:
>>> On 04/27/2014 02:55 PM, Rafael J. Wysocki wrote:

[ ... ]

> ---
> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> Subject: cpuidle / menu: Return (-1) if there are no suitable states
>
> If there is a PM QoS latency limit and all of the sufficiently shallow
> C-states are disabled, the cpuidle menu governor returns 0 which on
> some systems is CPUIDLE_DRIVER_STATE_START and shouldn't be returned
> if that C-state has been disabled.
>
> Fix the issue by modifying the menu governor to return (-1) in such
> situations.
>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> ---
> drivers/cpuidle/governors/menu.c | 2 +-
> include/linux/cpuidle.h | 2 ++
> 2 files changed, 3 insertions(+), 1 deletion(-)
>
> Index: linux-pm/drivers/cpuidle/governors/menu.c
> ===================================================================
> --- linux-pm.orig/drivers/cpuidle/governors/menu.c
> +++ linux-pm/drivers/cpuidle/governors/menu.c
> @@ -296,7 +296,7 @@ static int menu_select(struct cpuidle_dr
> data->needs_update = 0;
> }
>
> - data->last_state_idx = 0;
> + data->last_state_idx = CPUIDLE_DRIVER_STATE_START - 1;

In case of x86, CPUIDLE_DRIVER_STATE_START will be 1, so the select
function could return 0 even this one is disabled and this is not what
you want to happen, no ?


> /* Special case when user has set very strict latency requirement */
> if (unlikely(latency_req == 0))
>


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