linux-kernel - Re: PM / Wakeup: Introduce wakeup source objects and event statistics (v2)

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Message-Id: <201009170254.19753.rjw@sisk.pl>
Date:	Fri, 17 Sep 2010 02:54:19 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Kevin Hilman <khilman@...prootsystems.com>
Cc:	Alan Stern <stern@...land.harvard.edu>,
	Arve Hjønnevåg <arve@...roid.com>,
	"Linux-pm mailing list" <linux-pm@...ts.linux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: PM / Wakeup: Introduce wakeup source objects and event statistics (v2)

On Friday, September 17, 2010, Kevin Hilman wrote:
> "Rafael J. Wysocki" <rjw@...k.pl> writes:
> 
> > From: Rafael J. Wysocki <rjw@...k.pl>
> > Subject: PM / Wakeup: Introduce wakeup source objects and event statistics (v2)
> >
> > Introduce struct wakeup_source for representing system wakeup sources
> > within the kernel and for collecting statistics related to them.
> > Make the recently introduced helper functions pm_wakeup_event(),
> > pm_stay_awake() and pm_relax() use struct wakeup_source objects
> > internally, so that wakeup statistics associated with wakeup devices
> > can be collected and reported in a consistent way (the definition of
> > pm_relax() is changed, which is harmless, because this function is
> > not called directly by anyone yet).  Introduce new wakeup-related
> > sysfs device attributes in /sys/devices/.../power for reporting the
> > device wakeup statistics.
> >
> > Change the global wakeup events counters event_count and
> > events_in_progress into atomic variables, so that it is not necessary
> > to acquire a global spinlock in pm_wakeup_event(), pm_stay_awake()
> > and pm_relax(), which should allow us to avoid lock contention in
> > these functions on SMP systems with many wakeup devices.
> >
> > Signed-off-by: Rafael J. Wysocki <rjw@...k.pl>
> 
> Hi Rafael,
> 
> This looks like a really useful feature.

Great!

> Was doing some experiments with this on OMAP, and found a minor
> cut-and-paste bug in the Documentation file:
> 
> [...]
> 
> > +What:		/sys/devices/.../power/wakeup_max_time_ms
> > +Date:		September 2010
> > +Contact:	Rafael J. Wysocki <rjw@...k.pl>
> > +Description:
> > +		The /sys/devices/.../wakeup_max_time_ms attribute contains
> > +		the maximum time of processing a single wakeup event associated
> > +		with the device, in milliseconds.  This attribute is read-only.
> > +		If the device is not enabled to wake up the system from sleep
> > +		states, this attribute is empty.
> > +
> > +What:		/sys/devices/.../power/wakeup_max_time_ms
>                                                       ^^^
> s/max/last/ for this one.

Ah, thanks a lot.

> > +Date:		September 2010
> > +Contact:	Rafael J. Wysocki <rjw@...k.pl>
> > +Description:
> > +		The /sys/devices/.../wakeup_last_time_ms attribute contains
> > +		the value of the monotonic clock corresponding to the time of
> > +		signaling the last wakeup event associated with the device, in
> > +		milliseconds.  This attribute is read-only.  If the device is
> > +		not enabled to wake up the system from sleep states, this
> > +		attribute is empty.

Rafael
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