| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-id: <54928108.5080603@samsung.com>
Date: Thu, 18 Dec 2014 16:23:52 +0900
From: Chanwoo Choi <cw00.choi@...sung.com>
To: myungjoo.ham@...sung.com
Cc: 김국진 <kgene.kim@...sung.com>,
박경민 <kyungmin.park@...sung.com>,
"rafael.j.wysocki@...el.com" <rafael.j.wysocki@...el.com>,
"mark.rutland@....com" <mark.rutland@....com>,
ABHILASH KESAVAN <a.kesavan@...sung.com>,
"tomasz.figa@...il.com" <tomasz.figa@...il.com>,
Krzysztof Kozlowski <k.kozlowski@...sung.com>,
대인기 <inki.dae@...sung.com>,
"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
"linux-samsung-soc@...r.kernel.org"
<linux-samsung-soc@...r.kernel.org>
Subject: Re: [PATCHv4 1/8] devfreq: event: Add new devfreq_event class to
provide basic data for devfreq governor
Dear Myungjoo,
Thanks for your review.
On 12/18/2014 03:24 PM, MyungJoo Ham wrote:
> Hi Chanwoo,
>
> I love the idea and I now have a little mechanical issues in your code.
>
>> ---
>> drivers/devfreq/Kconfig | 2 +
>> drivers/devfreq/Makefile | 5 +-
>> drivers/devfreq/devfreq-event.c | 449 ++++++++++++++++++++++++++++++++++++++++
>> drivers/devfreq/event/Makefile | 1 +
>> include/linux/devfreq.h | 160 ++++++++++++++
>> 5 files changed, 616 insertions(+), 1 deletion(-)
>> create mode 100644 drivers/devfreq/devfreq-event.c
>> create mode 100644 drivers/devfreq/event/Makefile
>>
>> diff --git a/drivers/devfreq/Kconfig b/drivers/devfreq/Kconfig
>> index faf4e70..4d15b62 100644
>> --- a/drivers/devfreq/Kconfig
>> +++ b/drivers/devfreq/Kconfig
>> @@ -87,4 +87,6 @@ config ARM_EXYNOS5_BUS_DEVFREQ
>> It reads PPMU counters of memory controllers and adjusts the
>> operating frequencies and voltages with OPP support.
>>
>> +comment "DEVFREQ Event Drivers"
>> +
>> endif # PM_DEVFREQ
>> diff --git a/drivers/devfreq/Makefile b/drivers/devfreq/Makefile
>> index 16138c9..a1ffabe 100644
>> --- a/drivers/devfreq/Makefile
>> +++ b/drivers/devfreq/Makefile
>> @@ -1,4 +1,4 @@
>> -obj-$(CONFIG_PM_DEVFREQ) += devfreq.o
>> +obj-$(CONFIG_PM_DEVFREQ) += devfreq.o devfreq-event.o
>> obj-$(CONFIG_DEVFREQ_GOV_SIMPLE_ONDEMAND) += governor_simpleondemand.o
>> obj-$(CONFIG_DEVFREQ_GOV_PERFORMANCE) += governor_performance.o
>> obj-$(CONFIG_DEVFREQ_GOV_POWERSAVE) += governor_powersave.o
>> @@ -7,3 +7,6 @@ obj-$(CONFIG_DEVFREQ_GOV_USERSPACE) += governor_userspace.o
>> # DEVFREQ Drivers
>> obj-$(CONFIG_ARM_EXYNOS4_BUS_DEVFREQ) += exynos/
>> obj-$(CONFIG_ARM_EXYNOS5_BUS_DEVFREQ) += exynos/
>> +
>> +# DEVFREQ Event Drivers
>> +obj-$(CONFIG_PM_DEVFREQ) += event/
>>
>
> It looks getting mature fast.
> However, I would like to suggest you to
>
> allow not to compile devfreq-event.c and not include its compiled object
> if devfreq.c is required but devfreq-event.c is not required.
> (e.g., add CONFIG_PM_DEVFREQ_EVENT and let it be enabled when needed)
> just a little concern for lightweight devices.
> (this change might require a bit more work on the header as well)
> - Or do you think devfreq-event.c will become almost mandatory for
> most devfreq drivers?
I agree your opinion.
I'll add CONFIG_PM_DEVFREQ_EVENT according to your comment.
>
>
> [snip]
>
>> diff --git a/drivers/devfreq/devfreq-event.c b/drivers/devfreq/devfreq-event.c
>> new file mode 100644
>> index 0000000..0e1948e
>> --- /dev/null
>> +++ b/drivers/devfreq/devfreq-event.c
>> @@ -0,0 +1,449 @@
>> +/*
>> + * devfreq-event: Generic DEVFREQ Event class driver
>
> DEVFREQ is a generic DVFS mechanism (or subsystem).
>
> Plus, I thought devfreq-event is considered to be a "framework"
> for devfreq event class drivers. Am I mistaken?
You're right. just "class driver" description is not proper.
I'll modify the description of devfreq-event.c as following:
or If you have other opinion, would you please let me know about it?
devfreq-event: DEVFREQ-Event Framework to provide raw data of Non-CPU Devices.
> [snip]
>
>> +struct devfreq_event_dev *devfreq_event_add_edev(struct device *dev,
>> + struct devfreq_event_desc *desc)
>> +{
>> + struct devfreq_event_dev *edev;
>> + static atomic_t event_no = ATOMIC_INIT(0);
>> + int ret;
>> +
>> + if (!dev || !desc)
>> + return ERR_PTR(-EINVAL);
>> +
>> + if (!desc->name || !desc->ops)
>> + return ERR_PTR(-EINVAL);
>> +
>> + if (!desc->ops->set_event || !desc->ops->get_event)
>> + return ERR_PTR(-EINVAL);
>> +
>> + edev = devm_kzalloc(dev, sizeof(*edev), GFP_KERNEL);
>> + if (!edev)
>> + return ERR_PTR(-ENOMEM);
>> +
>> + mutex_lock(&devfreq_event_list_lock);
>
> You seem to lock that global lock too long. That lock is only required
> while you operate the list. The data to be protected by this mutex is
> devfreq_event_list. Until the new entry is added to the list, the new
> entry is free from protection. (may be delayed right before list_add)
OK. I'll move global lock right before calling list_add() on below.
>
>> + mutex_init(&edev->lock);
>> + edev->desc = desc;
>> + edev->dev.parent = dev;
>> + edev->dev.class = devfreq_event_class;
>> + edev->dev.release = devfreq_event_release_edev;
>> +
>> + dev_set_name(&edev->dev, "event.%d", atomic_inc_return(&event_no) - 1);
>> + ret = device_register(&edev->dev);
>> + if (ret < 0) {
>> + put_device(&edev->dev);
>> + mutex_unlock(&devfreq_event_list_lock);
>> + return ERR_PTR(ret);
>> + }
>> + dev_set_drvdata(&edev->dev, edev);
>> +
>> + INIT_LIST_HEAD(&edev->node);
>> + list_add(&edev->node, &devfreq_event_list);
>> + mutex_unlock(&devfreq_event_list_lock);
>> +
>> + return edev;
>> +}
>
>
>
> [snip / reversed maybe.. sorry]
>
>> +/**
>> + * devfreq_event_is_enabled() - Check whether devfreq-event dev is enabled or
>> + * not.
>> + * @edev : the devfreq-event device
>> + *
>> + * Note that this function check whether devfreq-event dev is enabled or not.
>> + * If return true, the devfreq-event dev is enabeld. If return false, the
>> + * devfreq-event dev is disabled.
>> + */
>> +bool devfreq_event_is_enabled(struct devfreq_event_dev *edev)
>> +{
>> + bool enabled = false;
>> +
>> + if (!edev || !edev->desc)
>> + return enabled;
>> +
>> + mutex_lock(&edev->lock);
>> +
>> + if (edev->enable_count > 0)
>> + enabled = true;
>> +
>> + if (edev->desc->ops && edev->desc->ops->is_enabled)
>> + enabled |= edev->desc->ops->is_enabled(edev);
>
> What does it mean when enabled_count > 0 and ops->is_enabled() is false? or..
> What does it mean when enabled_count = 0 and ops->is_enabled() is true?
>
> If you do enable_count in the subsystem, why would we rely on
> ops->is_enabled()? Are you assuming that a device MAY turn itself off
> without any kernel control (ops->disable()) and it is still a correct
> behabior?
You're right. devfreq_event_is_enabled() has ambiguous operation according to your comment.
I'll only control the enable_count in the subsystem without ops->is_enabled()
and then remove the is_enabled function in the structre devfreq_event_ops.
Best Regards,
Chanwoo Choi
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists