linux-kernel - Re: [PATCH 15/24] thunderbolt: Rework control channel to be more reliable

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Message-ID: <20170525143536.GT8541@lahna.fi.intel.com>
Date:   Thu, 25 May 2017 17:35:36 +0300
From:   Mika Westerberg <mika.westerberg@...ux.intel.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Andreas Noever <andreas.noever@...il.com>,
        Michael Jamet <michael.jamet@...el.com>,
        Yehezkel Bernat <yehezkel.bernat@...el.com>,
        Lukas Wunner <lukas@...ner.de>,
        Amir Levy <amir.jer.levy@...el.com>,
        Andy Lutomirski <luto@...nel.org>, Mario.Limonciello@...l.com,
        Jared.Dominguez@...l.com,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 15/24] thunderbolt: Rework control channel to be more
 reliable

On Thu, May 25, 2017 at 03:25:46PM +0200, Greg Kroah-Hartman wrote:
> > +/**
> > + * tb_cfg_request_put() - Decrease refcount and possibly release the request
> > + * @req: Request whose refcount is decreased
> > + *
> > + * Call this function when you are done with the request. When refcount
> > + * goes to %0 the object is released.
> > + */
> > +void tb_cfg_request_put(struct tb_cfg_request *req)
> > +{
> > +	kref_put(&req->kref, tb_cfg_request_destroy);
> > +}
> 
> What prevents this call from being called twice on the same object from
> different threads at the same time?  You still need a lock somewhere to
> protect yourself from that, am I just missing where that lock is?

No, you are right - it is missing a lock. I will add it there in the
next version.

Thanks.