linux-kernel - Re: dma-debug: add a check dma memory leaks

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Date:	Sun, 10 May 2009 11:46:24 +1000
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	David Woodhouse <dwmw2@...radead.org>
Cc:	Joerg Roedel <joerg.roedel@....com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	reinette.chatre@...el.com, greg@...ah.com
Subject: Re: dma-debug: add a check dma memory leaks

On Sun, 2009-05-10 at 00:59 +0100, David Woodhouse wrote:
> Subject: Add BUS_NOTIFY_UNBOUND_DRIVER callback after driver removal
> 
> This adds a notifier callback which happens _after_ the driver has been
> unbound from the device, needed for things like the DMA debugging API
> which want to check that all DMA mappings have been correctly torn down.
> 
> Signed-off-by: David Woodhouse <David.Woodhouse@...el.com>

Acked-by: Benjamin Herrenschmidt <benh@...nel.crashing.org>

> ---
> On Tue, 2009-04-21 at 11:20 +0200, Joerg Roedel wrote:
> > On Fri, Apr 17, 2009 at 10:51:05PM +0100, David Woodhouse wrote:
> > > Hm, cute... but not quite functioning as you intended. If you look at
> > > __device_release_driver() in drivers/base/dd.c you'll see it actually
> > > calls the notifier _before_ calling into the driver's ->remove() method.
> > > So it's hardly surprising that not everything has been freed yet...
> > > 
> > > Reported by Reinette when it bit iwlwifi.
> > > 
> > > Ben, can we get away with changing the order so that the ->remove() is
> > > called before the notifier, in this case?
> > 
> > Ben? I would like to keep this check. If its not possible to move this
> > one behind the drivers ->remove function it may be an option to add
> > another notifier?
> 
> It doesn't look like it's possible to move the UNBIND callback. Let's
> add an UNBOUND callback instead... I've tested this and it fixes the
> false positives.
> 
> Jörg, should you be using UNBOUND instead of UNBIND in the amd_iommu
> notifier callback too?
> 
> diff --git a/drivers/base/dd.c b/drivers/base/dd.c
> index 742cbe6..efd00de 100644
> --- a/drivers/base/dd.c
> +++ b/drivers/base/dd.c
> @@ -320,6 +320,10 @@ static void __device_release_driver(struct device *dev)
>  		devres_release_all(dev);
>  		dev->driver = NULL;
>  		klist_remove(&dev->p->knode_driver);
> +		if (dev->bus)
> +			blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
> +						     BUS_NOTIFY_UNBOUND_DRIVER,
> +						     dev);
>  	}
>  }
>  
> diff --git a/include/linux/device.h b/include/linux/device.h
> index 6a69caa..4ded2ae 100644
> --- a/include/linux/device.h
> +++ b/include/linux/device.h
> @@ -116,6 +116,7 @@ extern int bus_unregister_notifier(struct bus_type *bus,
>  #define BUS_NOTIFY_BOUND_DRIVER		0x00000003 /* driver bound to device */
>  #define BUS_NOTIFY_UNBIND_DRIVER	0x00000004 /* driver about to be
>  						      unbound */
> +#define BUS_NOTIFY_UNBOUND_DRIVER	0x00000005 /* driver has been unbound */
>  
>  extern struct kset *bus_get_kset(struct bus_type *bus);
>  extern struct klist *bus_get_device_klist(struct bus_type *bus);
> 
> 

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