linux-kernel - Re: [RFC][PATCH 8/8] PM / Sleep: Add user space interface for manipulating wakeup sources

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Date:	Thu, 26 Apr 2012 20:57:22 -0700
From:	Arve Hjønnevåg <arve@...roid.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	NeilBrown <neilb@...e.de>, John Stultz <johnstul@...ibm.com>,
	Linux PM list <linux-pm@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Magnus Damm <magnus.damm@...il.com>, markgross@...gnar.org,
	Matthew Garrett <mjg@...hat.com>,
	Greg KH <gregkh@...uxfoundation.org>,
	John Stultz <john.stultz@...aro.org>,
	Brian Swetland <swetland@...gle.com>,
	Alan Stern <stern@...land.harvard.edu>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
Subject: Re: [RFC][PATCH 8/8] PM / Sleep: Add user space interface for
 manipulating wakeup sources

2012/4/26 Rafael J. Wysocki <rjw@...k.pl>:
...
> ---
> From: Rafael J. Wysocki <rjw@...k.pl>
> Subject: PM / Sleep: Add user space interface for manipulating wakeup sources, v3
>
> Android allows user space to manipulate wakelocks using two
> sysfs file located in /sys/power/, wake_lock and wake_unlock.
> Writing a wakelock name and optionally a timeout to the wake_lock
> file causes the wakelock whose name was written to be acquired (it
> is created before is necessary), optionally with the given timeout.
> Writing the name of a wakelock to wake_unlock causes that wakelock
> to be released.
>
> Implement an analogous interface for user space using wakeup sources.
> Add the /sys/power/wake_lock and /sys/power/wake_unlock files
> allowing user space to create, activate and deactivate wakeup
> sources, such that writing a name and optionally a timeout to
> wake_lock causes the wakeup source of that name to be activated,
> optionally with the given timeout.  If that wakeup source doesn't
> exist, it will be created and then activated.  Writing a name to
> wake_unlock causes the wakeup source of that name, if there is one,
> to be deactivated.  Wakeup sources created with the help of
> wake_lock that haven't been used for more than 5 minutes are garbage
> collected and destroyed.  Moreover, there can be only WL_NUMBER_LIMIT

I think it would be better if the garbage collection and limit was
configurable and optional. I would probably turn both features off
since I do not want to chase down bugs because a wakelock was ignored,
and I think the garbage collection will erase stats that we care
about.

-- 
Arve Hjønnevåg
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