Re: [boost] [thread] countdown_latch

27 Apr 2013


      Le 27/04/13 09:51, Michael Marcin a écrit :
...
On 4/27/2013 2:05 AM, Vicente J. Botet Escriba wrote:
...
The change set is https://svn.boost.org/trac/boost/changeset/84055. To
see the sources, you would need to update the trunk or to take a look at
https://svn.boost.org/svn/boost/trunk/boost/thread/
Please let me know what do you think.
I think in latch your wait_for and wait_until don't work correctly in 
the case of spurious wakes.
You are right, my implementation needs a loop  (I didn't tested it).
The easy answer to this is probably use the predicate versions, which 
will also handle the technicalities of turning wait_for into 
wait_until during loops caused by spurious wakes.
like:
struct count_not_zero
{
    count_not_zero(const std::size_t& count_) : count(count_) {}
    bool operator()() const { return count != 0; }
    const std::size_t& count;
};
template 
cv_status wait_for(const chrono::duration& rel_time)
{
    boost::unique_lockboost::mutex lk(mutex_);
    return cond_.wait_for(rel_time, count_not_zero(count_));
}
template 
cv_status wait_until(const chrono::time_point& abs_time)
{
    boost::unique_lockboost::mutex lk(mutex_);
    return cond_.wait_until(abs_time, count_not_zero(count_));
}
Yes this would work much better ;-)
...
You should probably also add a latch_any to go along with 
condition_variable_any.
Why? the use of the condition_variable is an internal detail and more 
efficient than condition_variable_any. How latch_any could profit of an 
internal change?

Thanks,
Vicente