linux-kernel - Re: [PATCH 1/3] cpuidle: coupled: disable interrupts after entering safe state

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Date:	Thu, 29 Aug 2013 12:20:14 +0530
From:	Prashant Gaikwad <pgaikwad@...dia.com>
To:	Colin Cross <ccross@...roid.com>
CC:	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Neil Zhang <zhangwm@...vell.com>,
	Joseph Lo <josephl@...dia.com>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	"stable@...r.kernel.org" <stable@...r.kernel.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Daniel Lezcano <daniel.lezcano@...aro.org>
Subject: Re: [PATCH 1/3] cpuidle: coupled: disable interrupts after entering
 safe state

On Saturday 24 August 2013 01:15 AM, Colin Cross wrote:
> Calling cpuidle_enter_state is expected to return with interrupts
> enabled, but interrupts must be disabled before starting the
> ready loop synchronization stage.  Call local_irq_disable after
> each call to cpuidle_enter_state for the safe state.
>
> CC: stable@...r.kernel.org
> Signed-off-by: Colin Cross <ccross@...roid.com>
> ---
>   drivers/cpuidle/coupled.c | 2 ++
>   1 file changed, 2 insertions(+)
>
> diff --git a/drivers/cpuidle/coupled.c b/drivers/cpuidle/coupled.c
> index 2a297f8..db92bcb 100644
> --- a/drivers/cpuidle/coupled.c
> +++ b/drivers/cpuidle/coupled.c
> @@ -460,6 +460,7 @@ int cpuidle_enter_state_coupled(struct cpuidle_device *dev,
>   		}
>   		entered_state = cpuidle_enter_state(dev, drv,
>   			dev->safe_state_index);
> +		local_irq_disable();

Colin,

There is still some window where irq remains enabled after exiting safe 
state. It may introduce some corner case.
Instead of this can we pass a parameter to cpuidle_enter_state 
indicating that irq has to be enabled or not after exit from idle state, 
which would be false when entering safe state from coupled idle.

>   	}
>   
>   	/* Read barrier ensures online_count is read after prevent is cleared */
> @@ -485,6 +486,7 @@ retry:
>   
>   		entered_state = cpuidle_enter_state(dev, drv,
>   			dev->safe_state_index);
> +		local_irq_disable();
>   	}
>   
>   	if (cpuidle_coupled_clear_pokes(dev->cpu)) {

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