linux-kernel - Re: [PATCH 1/2] drivers: cpuidle: remove stale irq disabling call in cpuidle_enter

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Date:	Wed, 25 Feb 2015 15:13:23 +0100
From:	Daniel Lezcano <daniel.lezcano@...aro.org>
To:	Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
CC:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Subject: Re: [PATCH 1/2] drivers: cpuidle: remove stale irq disabling call
 in cpuidle_enter_freeze()

On 02/24/2015 06:58 PM, Lorenzo Pieralisi wrote:
> On return from cpuidle_enter_freeze() irqs are re-enabled by the function
> caller (ie cpuidle_idle_call) in the idle loop. This patch removes a stale
> local_irq_disable() call and its stale comment in cpuidle_enter_freeze(),
> since they disagree and do not serve a useful purpose.
>
> Cc: Rafael J. Wysocki <rjw@...ysocki.net>
> Cc: Daniel Lezcano <daniel.lezcano@...aro.org>
> Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@....com>
> ---
>   drivers/cpuidle/cpuidle.c | 3 ---
>   1 file changed, 3 deletions(-)
>
> diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
> index 4d53458..f47edc6c 100644
> --- a/drivers/cpuidle/cpuidle.c
> +++ b/drivers/cpuidle/cpuidle.c
> @@ -144,9 +144,6 @@ void cpuidle_enter_freeze(void)
>   		cpuidle_enter(drv, dev, index);
>   	else
>   		arch_cpu_idle();
> -
> -	/* Interrupts are enabled again here. */
> -	local_irq_disable();
>   }

Hmm, I think Rafael added this prevent lockdep to raise a warning.

Otherwise, cpuidle_enter or arch_cpu_idle enables the irq again and then 
when exiting the cpu_idle_call, we enable them again, so leading to a 
lockdep WARN in trace_hardirqs_on_caller.

That said, if we have to do this, it may reveal something is wrong in 
the code.


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