Subject: Re: [boost] [thread] countdown_latch
From: Vicente J. Botet Escriba (vicente.botet_at_[hidden])
Date: 2013-05-14 01:46:01
Le 14/05/13 00:44, Gaetano Mendola a écrit :
>
> Unlocking as soon as possible is something it should happen whenever
> is possible, but basically you are doing this kind of optimization:
>
> instead of
>
> void foo() {
> boost::unique_lock<boost::mutex> lk(mutex_);
> ....
> return;
> }
>
> you are optimizing doing this:
>
> void foo() {
> boost::unique_lock<boost::mutex> lk(mutex_);
> ...
> lk.unlock;
> return;
> }
>
> and I'm asking, is it worth? Do you have an evidence of it ?
> Having say that do whatever you believe is better in terms of clarity
> and correctness.
> I have seen also that in a couple of points the unique_lock can be
> replaced by a lock_guard (and possibly declared const).
>
>
>
Sorry Gaetano,
I have an uncommitted version where
bool count_down(unique_lock<mutex> &lk)
/// pre_condition (count_.value_ > 0)
{
BOOST_ASSERT(count_.value_ > 0);
if (--count_.value_ == 0)
{
lk.unlock();
count_.cond_.notify_all(); // unlocked !!!
return true;
}
return false;
}
Maybe I'm wrong and I'm doing premature optimization and it is better to
use lock_guard and don't unlock before notifying.
As you point it is in any case clearer.
Measures would be needed :(
Thanks for your interest,
Vicente