On 01/14/2014 11:35 AM, Preeti U Murthy wrote:
> On PowerPC, in a particular test scenario, all the cpu idle states were
> disabled.
> Inspite of this it was observed that the idle state count of the shallowest
> idle state, snooze, was increasing.
>
> This is because the governor returns the idle state index as 0 even in
> scenarios when no idle state can be chosen. These scenarios could be when the
> latency requirement is 0 or as mentioned above when the user wants to disable
> certain cpu idle states at runtime. In the latter case, its possible that no
> cpu idle state is valid because the suitable states were disabled
> and the rest did not match the menu governor criteria to be chosen as the
> next idle state.
>
> This patch adds the code to indicate that a valid cpu idle state could not be
> chosen by the menu governor and reports back to arch so that it can take some
> default action.
>
> Signed-off-by: Preeti U Murthy <pre...@linux.vnet.ibm.com>
> ---
Acked-by: Deepthi Dharwar <deep...@linux.vnet.ibm.com>
>
> drivers/cpuidle/cpuidle.c | 6 +++++-
> drivers/cpuidle/governors/menu.c | 7 ++++---
> 2 files changed, 9 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
> index a55e68f..5bf06bb 100644
> --- a/drivers/cpuidle/cpuidle.c
> +++ b/drivers/cpuidle/cpuidle.c
> @@ -131,8 +131,9 @@ int cpuidle_idle_call(void)
>
> /* ask the governor for the next state */
> next_state = cpuidle_curr_governor->select(drv, dev);
> +
> + dev->last_residency = 0;
> if (need_resched()) {
> - dev->last_residency = 0;
> /* give the governor an opportunity to reflect on the outcome */
> if (cpuidle_curr_governor->reflect)
> cpuidle_curr_governor->reflect(dev, next_state);
> @@ -140,6 +141,9 @@ int cpuidle_idle_call(void)
> return 0;
> }
>
> + if (next_state < 0)
> + return -EINVAL;
> +
> trace_cpu_idle_rcuidle(next_state, dev->cpu);
>
> broadcast = !!(drv->states[next_state].flags & CPUIDLE_FLAG_TIMER_STOP);
> diff --git a/drivers/cpuidle/governors/menu.c
> b/drivers/cpuidle/governors/menu.c
> index cf7f2f0..6921543 100644
> --- a/drivers/cpuidle/governors/menu.c
> +++ b/drivers/cpuidle/governors/menu.c
> @@ -283,6 +283,7 @@ again:
> * menu_select - selects the next idle state to enter
> * @drv: cpuidle driver containing state data
> * @dev: the CPU
> + * Returns -1 when no idle state is suitable
> */
> static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device
> *dev)
> {
> @@ -292,17 +293,17 @@ static int menu_select(struct cpuidle_driver *drv,
> struct cpuidle_device *dev)
> int multiplier;
> struct timespec t;
>
> - if (data->needs_update) {
> + if (data->last_state_idx >= 0 && data->needs_update) {
> menu_update(drv, dev);
> data->needs_update = 0;
> }
>
> - data->last_state_idx = 0;
> + data->last_state_idx = -1;
> data->exit_us = 0;
>
> /* Special case when user has set very strict latency requirement */
> if (unlikely(latency_req == 0))
> - return 0;
> + return data->last_state_idx;
>
> /* determine the expected residency time, round up */
> t = ktime_to_timespec(tick_nohz_get_sleep_length());
>
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