From: daniel.lezcano@linaro•org (Daniel Lezcano)
To: linux-arm-kernel@lists•infradead.org
Subject: [V3 patch 06/19] cpuidle: make a single register function for all
Date: Tue, 23 Apr 2013 16:22:07 +0200 [thread overview]
Message-ID: <5176990F.5070605@linaro.org> (raw)
In-Reply-To: <51769316.9090309@ti.com>
On 04/23/2013 03:56 PM, Santosh Shilimkar wrote:
> On Tuesday 23 April 2013 07:13 PM, Daniel Lezcano wrote:
>> On 04/18/2013 10:48 AM, Santosh Shilimkar wrote:
>>> On Friday 12 April 2013 06:05 PM, Daniel Lezcano wrote:
>>>> The usual scheme to initialize a cpuidle driver on a SMP is:
>>>>
>>>> cpuidle_register_driver(drv);
>>>> for_each_possible_cpu(cpu) {
>>>> device = &per_cpu(cpuidle_dev, cpu);
>>>> cpuidle_register_device(device);
>>>> }
>>>>
>>> Not exactly related to $subject patch but the driver should
>>> be registered after all devices has been registered to avoid
>>> devices start using the idle state data as soon as it is
>>> registered. In multi CPU system, this race can easily happen.
>>
>> Could you elaborate what problems the system will be facing if a cpu
>> starts using the idle state data as soon as it is registered ?
>>
>> Is there a bug related to this ?
>>
> Ofcouse. In multi-CPU scenario, where CPU C-states needs co-ordination
> can just lead into unknown issues if all the CPUs are not already part
> registered.
Hmm, ok. I don't see a scenario, with the current code, where that could
occurs. The coupled idle state will wait for the other cpus to enter
idle before initiating a shutdown sequence and, so far, the other sync
algorithm (last man standing) are doing the same.
There are some systems with 1024 cpus, and I did not heard problems like
this.
Do you know a system where this problem occurred ? Or is it something
you suspect that can happen ?
That would be interesting to have a system where this race occurs in
order to check the modifications will solve the issue.
>>> Current CPUIDLE core layer is also written with the assumption
>>> that driver will be registered first and then the devices which
>>> is not mandatory as per typical drive/device model.
>>
>> Yes, that's true. The framework assumes cpuidle_register_driver is
>> called before cpuidle_register_device.
>>
>>> May be you can fix that part while you are creating this common
>>> wrapper.
>>
>> Personally, as that will modify the cpuidle core layer and the changes
>> are not obvious (because of the design of the code) I prefer to do that
>> in a separate patchset if it is worth to do it - if there is a bug
>> related to it, then there is no discussion, we have to do it :)
>>
> Sure. It would have been nice if you would have clarified that before
> posting the next version.
>
> You still need to fix the kernel doc in your v4 though.
Which one ? "s/accross/across" ?
Thanks
-- Daniel
--
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next prev parent reply other threads:[~2013-04-23 14:22 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-04-12 12:35 [V3 patch 00/19] cpuidle: code consolidation Daniel Lezcano
2013-04-12 12:35 ` [V3 patch 01/19] ARM: shmobile: cpuidle: remove shmobile_enter_wfi function Daniel Lezcano
2013-04-15 3:56 ` Simon Horman
2013-04-18 8:28 ` Santosh Shilimkar
2013-04-12 12:35 ` [V3 patch 02/19] ARM: shmobile: cpuidle: remove shmobile_enter_wfi prototype Daniel Lezcano
2013-04-15 3:56 ` Simon Horman
2013-04-18 8:30 ` Santosh Shilimkar
2013-04-18 8:56 ` Daniel Lezcano
2013-04-12 12:35 ` [V3 patch 03/19] ARM: OMAP3: remove cpuidle_wrap_enter Daniel Lezcano
2013-04-15 22:55 ` Kevin Hilman
2013-04-18 8:27 ` Santosh Shilimkar
2013-04-19 22:17 ` Kevin Hilman
2013-04-12 12:35 ` [V3 patch 04/19] cpuidle: remove en_core_tk_irqen flag Daniel Lezcano
2013-04-19 22:21 ` Kevin Hilman
2013-04-12 12:35 ` [V3 patch 05/19] ARM: ux500: cpuidle: replace for_each_online_cpu by for_each_possible_cpu Daniel Lezcano
2013-04-16 12:34 ` Linus Walleij
2013-04-18 8:38 ` Santosh Shilimkar
2013-04-12 12:35 ` [V3 patch 06/19] cpuidle: make a single register function for all Daniel Lezcano
2013-04-17 6:28 ` Daniel Lezcano
2013-04-18 8:48 ` Santosh Shilimkar
2013-04-23 13:43 ` Daniel Lezcano
2013-04-23 13:56 ` Santosh Shilimkar
2013-04-23 14:22 ` Daniel Lezcano [this message]
2013-04-23 15:07 ` Santosh Shilimkar
2013-04-23 15:21 ` Daniel Lezcano
2013-04-12 12:35 ` [V3 patch 07/19] ARM: ux500: cpuidle: use init/exit common routine Daniel Lezcano
2013-04-12 12:35 ` [V3 patch 08/19] ARM: at91: " Daniel Lezcano
2013-04-12 12:35 ` [V3 patch 09/19] ARM: OMAP3: " Daniel Lezcano
2013-04-18 8:49 ` Santosh Shilimkar
2013-04-19 22:19 ` Kevin Hilman
2013-04-12 12:35 ` [V3 patch 10/19] ARM: s3c64xx: " Daniel Lezcano
2013-04-22 6:32 ` Daniel Lezcano
2013-04-12 12:35 ` [V3 patch 11/19] ARM: tegra: " Daniel Lezcano
2013-04-12 12:35 ` [V3 patch 12/19] ARM: shmobile: " Daniel Lezcano
2013-04-15 3:56 ` Simon Horman
2013-04-12 12:35 ` [V3 patch 13/19] ARM: OMAP4: " Daniel Lezcano
2013-04-18 8:50 ` Santosh Shilimkar
2013-04-19 22:19 ` Kevin Hilman
2013-04-12 12:36 ` [V3 patch 14/19] ARM: tegra: cpuidle: use init/exit common routine for tegra2 Daniel Lezcano
2013-04-12 12:36 ` [V3 patch 15/19] ARM: tegra: cpuidle: use init/exit common routine for tegra3 Daniel Lezcano
2013-04-12 12:36 ` [V3 patch 16/19] ARM: calxeda: cpuidle: use init/exit common routine Daniel Lezcano
2013-04-12 12:36 ` [V3 patch 17/19] ARM: kirkwood: " Daniel Lezcano
2013-04-14 15:14 ` Andrew Lunn
2013-04-14 20:22 ` Daniel Lezcano
2013-04-22 7:01 ` Daniel Lezcano
2013-04-22 16:47 ` Andrew Lunn
2013-04-22 16:54 ` Daniel Lezcano
2013-04-12 12:36 ` [V3 patch 18/19] ARM: davinci: " Daniel Lezcano
2013-04-16 8:30 ` Sekhar Nori
2013-04-12 12:36 ` [V3 patch 19/19] ARM: imx: " Daniel Lezcano
2013-04-17 6:24 ` Daniel Lezcano
2013-04-17 7:15 ` Shawn Guo
2013-04-17 7:23 ` Daniel Lezcano
2013-04-17 7:39 ` Shawn Guo
2013-04-15 23:03 ` [V3 patch 00/19] cpuidle: code consolidation Kevin Hilman
2013-04-16 8:42 ` Daniel Lezcano
2013-04-19 22:44 ` Kevin Hilman
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