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

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Date:	Thu, 26 Feb 2015 17:39:46 +0100
From:	"Rafael J. Wysocki" <rafael@...nel.org>
To:	Lorenzo Pieralisi <lorenzo.pieralisi@....com>
Cc:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH 1/2] drivers: cpuidle: remove stale irq disabling call in cpuidle_enter_freeze()

On Thu, Feb 26, 2015 at 10:48 AM, Lorenzo Pieralisi
<lorenzo.pieralisi@....com> wrote:
> On Wed, Feb 25, 2015 at 11:36:10PM +0000, Rafael J. Wysocki wrote:
>> On Wednesday, February 25, 2015 02:39:17 PM Lorenzo Pieralisi wrote:
>> > On Wed, Feb 25, 2015 at 02:13:23PM +0000, Daniel Lezcano wrote:

[cut]

>> I'm not entirely against of re-arranging things here, but a patch like the
>> (untested) one below might be more appropriate.
>>
>> Rafael (who would appreciate it if people asked questions instead of sending
>> patches on a hunch).
>
> I understand that, I wanted to just send [patch 2], this patch was more
> a way to get a clarification than anything else, asking would have been more
> appropriate, sorry.
>
> Anyway, I did not like disabling IRQs to just re-enable them on function
> return, in particular the comment below seemed to apply to the following
> line, which is a bit misleading.

I see.

>
> /* Interrupts are enabled again here. */
> local_irq_disable();
>
>>
>>
>> ---
>>  drivers/cpuidle/cpuidle.c |    2 +-
>>  kernel/sched/idle.c       |    1 -
>>  2 files changed, 1 insertion(+), 2 deletions(-)
>>
>> Index: linux-pm/drivers/cpuidle/cpuidle.c
>> ===================================================================
>> --- linux-pm.orig/drivers/cpuidle/cpuidle.c
>> +++ linux-pm/drivers/cpuidle/cpuidle.c
>> @@ -132,6 +132,7 @@ void cpuidle_enter_freeze(void)
>>       index = cpuidle_find_deepest_state(drv, dev, true);
>>       if (index >= 0) {
>>               enter_freeze_proper(drv, dev, index);
>> +             local_irq_enable();
>>               return;
>>       }
>>
>> @@ -146,7 +147,6 @@ void cpuidle_enter_freeze(void)
>>               arch_cpu_idle();
>>
>>       /* Interrupts are enabled again here. */
>> -     local_irq_disable();
>>  }
>>
>>  /**
>> Index: linux-pm/kernel/sched/idle.c
>> ===================================================================
>> --- linux-pm.orig/kernel/sched/idle.c
>> +++ linux-pm/kernel/sched/idle.c
>> @@ -116,7 +116,6 @@ static void cpuidle_idle_call(void)
>>        */
>>       if (idle_should_freeze()) {
>>               cpuidle_enter_freeze();
>> -             local_irq_enable();
>>               goto exit_idle;
>>       }
>>
>
> It looks fine, I will test it. I would add a comment to
> cpuidle_enter_freeze() to document it must return with IRQs
> enabled.

OK

Rafael
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