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Date: Fri, 29 Jul 2016 14:48:38 -0700
From: Greg KH <gregkh@linuxfoundation.org>
To: Stephen Hemminger <stephen@networkplumber.org>
Cc: Amir Levy <amir.jer.levy@intel.com>, andreas.noever@gmail.com,
        bhelgaas@google.com, corbet@lwn.net, linux-kernel@vger.kernel.org,
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        mika.westerberg@intel.com, tomas.winkler@intel.com
Subject: Re: [PATCH v5 4/8] thunderbolt: Communication with the ICM (firmware)
Message-ID: <20160729214838.GA14827@kroah.com>
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 <20160729140224.137dbaac@xeon-e3>
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On Fri, Jul 29, 2016 at 02:02:24PM -0700, Stephen Hemminger wrote:
> On Thu, 28 Jul 2016 11:15:17 +0300
> Amir Levy <amir.jer.levy@intel.com> wrote:
> 
> > +static LIST_HEAD(controllers_list);
> > +static DECLARE_RWSEM(controllers_list_rwsem);
> 
> Why use a semaphore when simple spinlock or mutex would be better?

And never use a RW semaphore unless you can benchmark the difference
from a normal lock.  If you can't benchmark it, then don't use it...