linux-kernel - Re: [RFC PATCH 1/4] PM / QoS: Add pm_qos_cancel_request

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Date:	Tue, 21 Apr 2015 10:18:27 -0000
From:	"Dov Levenglick" <dovl@...eaurora.org>
To:	"Adrian Hunter" <adrian.hunter@...el.com>
Cc:	"Dov Levenglick" <dovl@...eaurora.org>,
	"Ulf Hansson" <ulf.hansson@...aro.org>,
	"linux-mmc" <linux-mmc@...r.kernel.org>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	"Len Brown" <len.brown@...el.com>, "Pavel Machek" <pavel@....cz>,
	"Kevin Hilman" <khilman@...aro.org>,
	"Tomeu Vizoso" <tomeu.vizoso@...labora.com>,
	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 1/4] PM / QoS: Add pm_qos_cancel_request_lazy() that
 doesn't sleep

> On 20/04/15 17:00, Dov Levenglick wrote:
>>> Add pm_qos_cancel_request_lazy() which is convenient for
>>> contexts that may not sleep.
>>>
>>> Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>
>>> ---
>>>  include/linux/pm_qos.h |  2 ++
>>>  kernel/power/qos.c     | 20 ++++++++++++++++++++
>>>  2 files changed, 22 insertions(+)
>>>
>>> diff --git a/include/linux/pm_qos.h b/include/linux/pm_qos.h
>>> index 7b3ae0c..f44d353 100644
>>> --- a/include/linux/pm_qos.h
>>> +++ b/include/linux/pm_qos.h
>>> @@ -126,6 +126,8 @@ void pm_qos_update_request(struct pm_qos_request
> *req,
>>>  			   s32 new_value);
>>>  void pm_qos_update_request_timeout(struct pm_qos_request *req,
>>>  				   s32 new_value, unsigned long
>>> timeout_us);
>>> +void pm_qos_cancel_request_lazy(struct pm_qos_request *req,
>>> +				unsigned int timeout_us);
>>>  void pm_qos_remove_request(struct pm_qos_request *req);
>>>
>>
>> I think that this could be acheived using existing API if
>> pm_qos_update_request_timeout() were to be called with the existing
>> timeout value.
>
> I don't follow what you mean. There is no existing timeout value.
> Did you mean existing request value? There is still the difference wrt
> cancel_delayed_work_sync.

I did mean the existing request value. Thanks.
There is also the cancel_delayed_work_sync, however I think that that
should be called in any case in order to cancel any other pending timeout
changes.

>
>> Since reading the existing timeout value is missing - and I think would
> be
>> a useful feature to have for other use-cases - do you agree with such an
>> approach?
>>
>>>  int pm_qos_request(int pm_qos_class);
>>> diff --git a/kernel/power/qos.c b/kernel/power/qos.c
>>> index 97b0df7..ac131cb 100644
>>> --- a/kernel/power/qos.c
>>> +++ b/kernel/power/qos.c
>>> @@ -517,6 +517,26 @@ void pm_qos_update_request_timeout(struct
>>> pm_qos_request *req, s32 new_value,
>>>  }
>>>
>>>  /**
>>> + * pm_qos_cancel_request_lazy - cancels an existing qos request
> lazily.
>>> + * @req : handle to list element holding a pm_qos request to use
>>> + * @timeout_us: the delay before cancelling this qos request in usecs.
>>> + *
>>> + * After timeout_us, this qos request is cancelled.
>>> + */
>>> +void pm_qos_cancel_request_lazy(struct pm_qos_request *req,
>>> +				unsigned int timeout_us)
>>> +{
>>> +	if (!req)
>>> +		return;
>>> +	if (WARN(!pm_qos_request_active(req),
>>> +		 "%s called for unknown object.", __func__))
>>> +		return;
>>> +
>>> +	schedule_delayed_work(&req->work, usecs_to_jiffies(timeout_us));
>>> +}
>>> +EXPORT_SYMBOL_GPL(pm_qos_cancel_request_lazy);
>>> +
>>> +/**
>>>   * pm_qos_remove_request - modifies an existing qos request
>>>   * @req: handle to request list element
>>>   *
>>> --
>>> 1.9.1
>>>
>>> --
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>>>
>>
>>
>> QUALCOMM ISRAEL, on behalf of Qualcomm Innovation Center, Inc.
>> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora
> Forum,
>> a Linux Foundation Collaborative Project
>>
>>
>>
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-mmc" in
> the body of a message to majordomo@...r.kernel.org
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>


QUALCOMM ISRAEL, on behalf of Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

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