Re: [PATCHv2] attr: convert to new threadsafe API

> On Wed, Oct 12, 2016 at 2:38 PM, Junio C Hamano <gitster@pobox.com> wrote:
>> 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.
>
> Having followed that advice (and internally having a DCLP), I think
> we have Triple Checked Locking Pattern in this patch.  Nobody wrote
> a paper on how that would not work, yet. ;)
>
> In the reroll I plan to reduce it to a Single Checked (inside a mutex)
> Locking Pattern, though I would expect that performance (or lack thereof)
> will show then. But let's postpone measuring until we have a working patch.