linux-kernel - Re: [char-misc-next V3] mei: add reference counting for me clients

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Message-ID: <20141106022010.GD17253@kroah.com>
Date:	Wed, 5 Nov 2014 18:20:10 -0800
From:	Greg KH <gregkh@...uxfoundation.org>
To:	"Winkler, Tomas" <tomas.winkler@...el.com>
Cc:	"arnd@...db.de" <arnd@...db.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [char-misc-next V3] mei: add reference counting for me clients

On Tue, Nov 04, 2014 at 05:22:51AM +0000, Winkler, Tomas wrote:
> > 
> > On Mon, Nov 03, 2014 at 10:42:05AM +0200, Tomas Winkler wrote:
> > > To support dynamic addition/remove we add reference
> > > counter.
> > 
> > What is keeping two different threads / cpus from grabbing a reference
> > at the same time the other one is dropping it?
> > 
> > You have a list here, with no locking, right?  You also don't have any
> > locking for your kref, which isn't good at all...
> > 
> > Please audit and fix up.
> 
> Of course there is a lock, it wouldn't work at all. It is not explicit
> but we run under device_lock mutex. 

Please make it explicit :)

thanks,

greg k-h
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