linux-kernel - Re: [PATCH] PM: Avoid false-positive warnings in dev_pm_domain

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Message-ID: <1454336144.32507.15.camel@linux.intel.com>
Date:	Mon, 01 Feb 2016 16:15:44 +0200
From:	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Linux PM list <linux-pm@...r.kernel.org>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Tomeu Vizoso <tomeu.vizoso@...labora.com>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	Kevin Hilman <khilman@...nel.org>
Subject: Re: [PATCH] PM: Avoid false-positive warnings in dev_pm_domain_set()

On Sat, 2016-01-30 at 12:54 +0100, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> There is a WARN_ON() in dev_pm_domain_set() that triggers on attempts
> to set the pm_domain pointer for devices with a driver bound.
> 
> However, that WARN_ON() triggers on attempts to clear the pointer
> too and the test it uses is based on checking the device's
> p->knode_driver pointer which still is set when the device bus
> type's/driver's ->remove callback has been executed.  This
> leads to false-positive warnings when bus type code calls
> dev_pm_domain_set() to clear the pm_domain pointer after
> invoking the driver's ->remove() callback.
> 
> To avoid those false-positives, make dev_pm_domain_set() check
> if the pointer passed to it is NULL and skip the warning in
> that case.

Tested on Intel Braswell where modprobe -r sdhci-acpi caused a warning
before this patch.

Tested-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>

> 
> Fixes: 989561de9b51 (PM / Domains: add setter for dev.pm_domain)
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
>  drivers/base/power/common.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> Index: linux-pm/drivers/base/power/common.c
> ===================================================================
> --- linux-pm.orig/drivers/base/power/common.c
> +++ linux-pm/drivers/base/power/common.c
> @@ -146,7 +146,7 @@ void dev_pm_domain_set(struct device *de
>  	if (dev->pm_domain == pd)
>  		return;
>  
> -	WARN(device_is_bound(dev),
> +	WARN(pd && device_is_bound(dev),
>  	     "PM domains can only be changed for unbound
> devices\n");
>  	dev->pm_domain = pd;
>  	device_pm_check_callbacks(dev);
> 

-- 
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Intel Finland Oy