Re: [PATCH] PM / Sleep: Print name of wakeup source that aborts suspend

["Rafael J. Wysocki" <rjw@sisk.pl>]

On Wednesday, July 18, 2012, Todd Poynor wrote:
> Print active wakeup sources, or the most recently active wakeup
> source, when a PM transition is aborted due to wakeup source
> events.
> 
> Signed-off-by: Todd Poynor <toddpoynor@google.com>
> ---
>  drivers/base/power/wakeup.c |   29 +++++++++++++++++++++++++++++
>  1 files changed, 29 insertions(+), 0 deletions(-)
> 
> A driver or app may repeatedly request a wakeup source while the system
> is attempting to enter suspend, which may indicate a bug or at least
> point out a highly active system component that is responsible for
> decreased battery life on a mobile device.  Even when the incidence
> of suspend abort is not severe, identifying wakeup sources that
> frequently abort suspend can be a useful clue for power management
> analysis.
> 
> In some cases the existing stats can point out the offender where there is
> an unexpectedly high activation count that stands out from the others, but
> in other cases the wakeup source frequently taken just after the rest of
> the system thinks its time to suspend might not stand out in the overall
> stats.
> 
> It is also often useful to have information about what's been happening
> recently, rather than totals of all activity for the system boot.
> 
> It's suggested to (optionally?) dump a line about which wakeup source
> aborted suspend to aid analysis of these situations.
> 
> diff --git a/drivers/base/power/wakeup.c b/drivers/base/power/wakeup.c
> index cbb463b..c079ffe 100644
> --- a/drivers/base/power/wakeup.c
> +++ b/drivers/base/power/wakeup.c
> @@ -649,6 +649,31 @@ void pm_wakeup_event(struct device *dev, unsigned int msec)
>  }
>  EXPORT_SYMBOL_GPL(pm_wakeup_event);
>  
> +static void print_active_wakeup_sources(void)
> +{
> +	struct wakeup_source *ws;
> +	int active = 0;
> +	struct wakeup_source *last_activity_ws = NULL;
> +
> +	rcu_read_lock();
> +	list_for_each_entry_rcu(ws, &wakeup_sources, entry) {
> +		if (ws->active) {
> +			pr_info("active wakeup source: %s\n", ws->name);
> +			active = 1;

Can we do a break here?  Or do we want to get all of them?

> +		} else if (!active &&
> +			   (!last_activity_ws ||
> +			    ws->last_time.tv64 >
> +			    last_activity_ws->last_time.tv64)) {

ktime_to_ns() anyone?

> +			last_activity_ws = ws;
> +		}
> +	}
> +
> +	if (!active && last_activity_ws)
> +		pr_info("last active wakeup source: %s\n",
> +			last_activity_ws->name);
> +	rcu_read_unlock();
> +}
> +
>  /**
>   * pm_wakeup_pending - Check if power transition in progress should be aborted.
>   *
> @@ -671,6 +696,10 @@ bool pm_wakeup_pending(void)
>  		events_check_enabled = !ret;
>  	}
>  	spin_unlock_irqrestore(&events_lock, flags);
> +
> +	if (ret)
> +		print_active_wakeup_sources();
> +
>  	return ret;
>  }

There is no way this or equivalent can go into v3.6.  It may go into v3.7,
but there's a plenty of time for that.

Thanks,
Rafael