linux-kernel - Re: [PATCH 3/3] PM / Runtime: Check device PM QoS setting before "no callbacks" check

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Date:	Wed, 15 Aug 2012 12:20:44 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
cc:	Linux PM list <linux-pm@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/3] PM / Runtime: Check device PM QoS setting before
 "no callbacks" check

On Tue, 14 Aug 2012, Rafael J. Wysocki wrote:

> 
> If __dev_pm_qos_read_value(dev) returns a negative value,
> rpm_suspend() should return -EPERM for dev even if its
> power.no_callbacks flag is set.  For this to happen, the device's
> power.no_callbacks flag has to be checked after the PM QoS check,
> so modify the code accordingly.
> 
> Signed-off-by: Rafael J. Wysocki <rjw@...k.pl>
> ---
>  drivers/base/power/runtime.c |   12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> Index: linux/drivers/base/power/runtime.c
> ===================================================================
> --- linux.orig/drivers/base/power/runtime.c
> +++ linux/drivers/base/power/runtime.c
> @@ -388,6 +388,12 @@ static int rpm_suspend(struct device *de
>  		goto repeat;
>  	}
>  
> +	if (__dev_pm_qos_read_value(dev) < 0) {
> +		/* Negative PM QoS constraint means "never suspend". */
> +		retval = -EPERM;
> +		goto out;
> +	}
> +
>  	if (dev->power.no_callbacks)
>  		goto no_callback;	/* Assume success. */
>  
> @@ -402,12 +408,6 @@ static int rpm_suspend(struct device *de
>  		goto out;
>  	}
>  
> -	if (__dev_pm_qos_read_value(dev) < 0) {
> -		/* Negative PM QoS constraint means "never suspend". */
> -		retval = -EPERM;
> -		goto out;
> -	}
> -
>  	__update_runtime_status(dev, RPM_SUSPENDING);
>  
>  	if (dev->pm_domain)

Wouldn't it be better to move the test into 
rpm_check_suspend_allowed()?  Then it would apply to idle notifications 
and pm_schedule_suspend().

Alan Stern

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