Re: patch usb-bus-mutex.patch added to gregkh-2.6 tree

On Mon, 9 Apr 2007 [email protected] wrote:

> 
> This is a note to let you know that I've just added the patch titled
> 
>      Subject: USB: remove use of the bus rwsem, as it doesn't really protect anything.
> 
> to my gregkh-2.6 tree.  Its filename is
> 
>      usb-bus-mutex.patch
> 
> This tree can be found at 
>     http://www.kernel.org/pub/linux/kernel/people/gregkh/gregkh-2.6/patches/
> 
> 
> From foo@baz Tue Apr  9 12:12:43 2002
> Date: Mon, 9 Apr 2007 11:52:31 -0400 (EDT)
> To: Greg KH <[email protected]>
> From: Greg Kroah-Hartman <[email protected]>
> Subject: USB: remove use of the bus rwsem, as it doesn't really protect anything.
> 
> The driver core stopped using the rwsem a long time ago, yet the USB
> core still grabbed the lock, thinking it protected something.  As a lock
> is really needed for these instances, I've replaced it with a local
> mutex to protect the bus, but odds are there is still a code path that
> needs to have this lock added to it to properly protect things.

Actually I don't think the new mutex is needed for protecting anything.  
All the areas covered by your patch are already protected by the device
lock (changes to bindings, interfaces, or configurations, addition or
removal of children) or the bus_list_lock (addition or removal of root
hubs).

BTW, there are a couple of references to usb_bus_type.subsys in comments 
in driver.c.  You might as well remove them too.

Alan Stern


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