linux-kernel - Re: [PATCH] ALSA: fix kernel panic in initialization of mpu401 driver

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Date:	Thu, 5 Oct 2006 11:57:11 +0200 (CEST)
From:	Jiri Kosina <jikos@...os.cz>
To:	Jaroslav Kysela <perex@...e.cz>
cc:	Castet Matthieu <castet.matthieu@...e.fr>,
	Takashi Iwai <tiwai@...e.de>,
	LKML <linux-kernel@...r.kernel.org>,
	ALSA development <alsa-devel@...a-project.org>,
	Andrew Morton <akpm@...l.org>,
	Alan Stern <stern@...land.harvard.edu>,
	Greg Kroah-Hartman <gregkh@...e.de>
Subject: Re: [PATCH] ALSA: fix kernel panic in initialization of mpu401 driver

On Thu, 5 Oct 2006, Jaroslav Kysela wrote:

> Unfortunately, I do not think that it's a proper solution. I think that 
> platform device layer should play more nicely and if probe() fails for a 
> reason and if platform_device_register_simple() does not set IS_ERR(), 
> then platform_device_unregister() must be callable to free all 
> resources.

I agree.

> I would reject this patch and fix drivers/base/bus.c. The problematic 
> change is in commit f2eaae197f4590c4d96f31b09b0ee9067421a95c and this 
> patch will probably fix it:
> [PATCH] drivers/base - check if device is registered before removal
> Without this fix platform_device_unregister() might oops.
> Signed-off-by: Jaroslav Kysela <perex@...e.cz>
> diff --git a/drivers/base/bus.c b/drivers/base/bus.c
> index 12173d1..daa2390 100644
> --- a/drivers/base/bus.c
> +++ b/drivers/base/bus.c
> @@ -428,8 +428,10 @@ void bus_remove_device(struct device * d
>  		sysfs_remove_link(&dev->kobj, "bus");
>  		sysfs_remove_link(&dev->bus->devices.kobj, dev->bus_id);
>  		device_remove_attrs(dev->bus, dev);
> -		dev->is_registered = 0;
> -		klist_del(&dev->knode_bus);
> +		if (dev->is_registered) {
> +			dev->is_registered = 0;
> +			klist_del(&dev->knode_bus);
> +		}
>  		pr_debug("bus %s: remove device %s\n", dev->bus->name, dev->bus_id);
>  		device_release_driver(dev);
>  		put_bus(dev->bus);

Yes, it (among other things) fixes the panic in MPU401 initialization.

Acked-by: Jiri Kosina <jikos@...os.cz>

-- 
Jiri Kosina
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