Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Sat, 6 Apr 2019 17:55:55 -0500
From:   Madhumthia Prabakaran <madhumithabiw@gmail.com>
To:     Dan Carpenter <dan.carpenter@oracle.com>, johan@kernel.org,
        elder@kernel.org, gregkh@linuxfoundation.org,
        greybus-dev@lists.linaro.org, devel@driverdev.osuosl.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] Staging: greybus: Fix spinlock_t definition without
 comment
Message-ID: <20190406225554.GA9140@madhuleo>
References: <20190405200046.20600-1-madhumithabiw@gmail.com>
 <20190405205304.GS32590@kadam>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20190405205304.GS32590@kadam>
User-Agent: Mutt/1.9.4 (2018-02-28)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Fri, Apr 05, 2019 at 11:53:04PM +0300, Dan Carpenter wrote:
> On Fri, Apr 05, 2019 at 03:00:46PM -0500, Madhumitha Prabakaran wrote:
> > Fix spinlock_t definition without comment.
> > 
> > Signed-off-by: Madhumitha Prabakaran <madhumithabiw@gmail.com>
> > ---
> >  drivers/staging/greybus/connection.h | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/staging/greybus/connection.h b/drivers/staging/greybus/connection.h
> > index 5ca3befc0636..0aedd246e94a 100644
> > --- a/drivers/staging/greybus/connection.h
> > +++ b/drivers/staging/greybus/connection.h
> > @@ -47,7 +47,7 @@ struct gb_connection {
> >  	unsigned long			flags;
> >  
> >  	struct mutex			mutex;
> > -	spinlock_t			lock;
> > +	spinlock_t			lock; /* Protect structure fields */
> >  	enum gb_connection_state	state;
> 
> What does the mutex do then?  Why can't we just use the spinlock for
> everything?

Here, mutexes protect spinlock_t for gb_connection_state fields and
gb_connection_state fields itself in struct gb_connection.

However, I wasn't sure then and now exactly, how to find out which resources in the
structure, the spinlock or mutex is performing kernel synchronization.

> 
> I did glance at the code and it wasn't immediately obvious to me.

Thanks for reviewing it.

> 
> regards,
> dan carpenter
>