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From:   Junio C Hamano <gitster@pobox.com>
To:     Johannes Sixt <j6t@kdbg.org>
Cc:     Stefan Beller <sbeller@google.com>, git@vger.kernel.org,
        bmwill@google.com
Subject: Re: [PATCHv2] attr: convert to new threadsafe API
References: <20161011235951.8358-1-sbeller@google.com>
        <44c554b8-7ac1-047d-59f0-b4d5331ed496@kdbg.org>
Date:   Wed, 12 Oct 2016 14:38:10 -0700
In-Reply-To: <44c554b8-7ac1-047d-59f0-b4d5331ed496@kdbg.org> (Johannes Sixt's
        message of "Wed, 12 Oct 2016 22:07:03 +0200")
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Johannes Sixt <j6t@kdbg.org> writes:

> Sigh. DCLP, the Double Checked Locking Pattern. ...
> I suggest you go without it, then measure, and only *then* optimize if
> it is a bottleneck. 

That comes from me in earlier discussion before the patch, namely in
<xmqqeg3m8y6y.fsf@gitster.mtv.corp.google.com>, where I wondered if
a cheap check outside the lock may be a possible optimization
opportunity, as this is a classic singleton that will not be
deinitialized, and once the codepath gets exercised, we would be
taking the "nothing to do" route 100% of the time.