Re: [PATCH 04/36] cpuidle,intel_idle: Fix CPUIDLE_FLAG_IRQ_ENABLE

Rafael J. Wysocki
2022-06-08T16:21:45Z

On Wed, Jun 8, 2022 at 4:47 PM Peter Zijlstra <peterz@infradead.org> wrote:
>
> Commit c227233ad64c ("intel_idle: enable interrupts before C1 on
> Xeons") wrecked intel_idle in two ways:
>
> - must not have tracing in idle functions
> - must return with IRQs disabled
>
> Additionally, it added a branch for no good reason.
>
> Fixes: c227233ad64c ("intel_idle: enable interrupts before C1 on Xeons")
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>

Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

And do I think correctly that this can be applied without the rest of
the series?

> ---
> drivers/idle/intel_idle.c | 48 +++++++++++++++++++++++++++++++++++-----------
> 1 file changed, 37 insertions(+), 11 deletions(-)
>
> --- a/drivers/idle/intel_idle.c
> +++ b/drivers/idle/intel_idle.c
> @@ -129,21 +137,37 @@ static unsigned int mwait_substates __in
> *
> * Must be called under local_irq_disable().
> */
> +
> -static __cpuidle int intel_idle(struct cpuidle_device *dev,
> - struct cpuidle_driver *drv, int index)
> +static __always_inline int __intel_idle(struct cpuidle_device *dev,
> + struct cpuidle_driver *drv, int index)
> {
> struct cpuidle_state *state = &drv->states[index];
> unsigned long eax = flg2MWAIT(state->flags);
> unsigned long ecx = 1; /* break on interrupt flag */
>
> - if (state->flags & CPUIDLE_FLAG_IRQ_ENABLE)
> - local_irq_enable();
> -
> mwait_idle_with_hints(eax, ecx);
>
> return index;
> }
>
> +static __cpuidle int intel_idle(struct cpuidle_device *dev,
> + struct cpuidle_driver *drv, int index)
> +{
> + return __intel_idle(dev, drv, index);
> +}
> +
> +static __cpuidle int intel_idle_irq(struct cpuidle_device *dev,
> + struct cpuidle_driver *drv, int index)
> +{
> + int ret;
> +
> + raw_local_irq_enable();
> + ret = __intel_idle(dev, drv, index);
> + raw_local_irq_disable();
> +
> + return ret;
> +}
> +
> /**
> * intel_idle_s2idle - Ask the processor to enter the given idle state.
> * @dev: cpuidle device of the target CPU.
> @@ -1801,6 +1824,9 @@ static void __init intel_idle_init_cstat
> /* Structure copy. */
> drv->states[drv->state_count] = cpuidle_state_table[cstate];
>
> + if (cpuidle_state_table[cstate].flags & CPUIDLE_FLAG_IRQ_ENABLE)
> + drv->states[drv->state_count].enter = intel_idle_irq;
> +
> if ((disabled_states_mask & BIT(drv->state_count)) ||
> ((icpu->use_acpi || force_use_acpi) &&
> intel_idle_off_by_default(mwait_hint) &&