linux-kernel - Re: [PATCH] driver core: fix shutdown races with probe/remove(v2)

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Message-ID: <Pine.LNX.4.44L0.1206111014010.1607-100000@iolanthe.rowland.org>
Date:	Mon, 11 Jun 2012 10:16:17 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Ming Lei <ming.lei@...onical.com>
cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	<linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<stable@...r.kernel.org>
Subject: Re: [PATCH] driver core: fix shutdown races with probe/remove(v2)

On Mon, 11 Jun 2012, Ming Lei wrote:

> @@ -1820,6 +1833,18 @@ void device_shutdown(void)
>  		list_del_init(&dev->kobj.entry);
>  		spin_unlock(&devices_kset->list_lock);
>  
> +		/* hold lock to avoid race with .probe/.release */
> +		if (dev->parent && !__try_lock(dev->parent))
> +			nonlocked = 2;
> +		else if (!__try_lock(dev))
> +			nonlocked = 1;
> +		else
> +			nonlocked = 0;
> +
> +		if (nonlocked)
> +			dev_err(dev, "can't hold %slock for shutdown\n",
> +					nonlocked == 1 ? "" : "parent ");

Even if the parent can't be locked, you should still try to lock the 
device.

Alan Stern

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