linux-kernel - Re: [PATCH] PM: Acquire device locks on suspend

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Message-ID: <Pine.LNX.4.44L0.0801061203510.7367-100000@netrider.rowland.org>
Date:	Sun, 6 Jan 2008 12:06:38 -0500 (EST)
From:	Alan Stern <stern@...land.harvard.edu>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
cc:	Greg KH <gregkh@...e.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Len Brown <lenb@...nel.org>, Ingo Molnar <mingo@...e.hu>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	pm list <linux-pm@...ts.linux-foundation.org>
Subject: Re: [PATCH] PM: Acquire device locks on suspend

On Sun, 6 Jan 2008, Rafael J. Wysocki wrote:

> > If you can figure out a way to disable the warning in device_del() for 
> > just the one device being unregistered by 
> > device_pm_destroy_suspended(),
> 
> Something like this, perhaps:
> 
> @@ -905,6 +915,18 @@ void device_del(struct device * dev)
>  	struct device * parent = dev->parent;
>  	struct class_interface *class_intf;
>  
> +	if (down_trylock(&dev->sem)) {
> +		if (pm_sleep_lock()) {
> +			dev_warn(dev, "Illegal %s during suspend\n",
> +				__FUNCTION__);
> +			dump_stack();
> +		} else {
> +			pm_sleep_unlock();
> +		}
> +	} else {
> +		up(&dev->sem);
> +	}
> +
>  	if (parent)
>  		klist_del(&dev->knode_parent);
>  	if (MAJOR(dev->devt))

Bizarre, but it should work.  Be sure to include plenty of explanatory 
comments -- otherwise nobody will be able to figure it out!  :-)

Alan Stern

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