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event/Loop: round epoll_wait() timeout up

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This implements proper rounding, amending commit dcbb9fe07c
This commit is contained in:
Max Kellermann 2019-03-05 22:06:09 +01:00 committed by Max Kellermann
parent 3ac87bbcda
commit 7d502fb448
1 changed files with 13 additions and 2 deletions
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15
src/event/Loop.cxx
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@ -162,6 +162,18 @@ EventLoop::HandleTimers() noexcept
return Event::Duration(-1); return Event::Duration(-1);
} }
template<class ToDuration, class Rep, class Period>
static constexpr ToDuration
duration_cast_round_up(std::chrono::duration<Rep, Period> d) noexcept
{
using FromDuration = decltype(d);
constexpr auto one = std::chrono::duration_cast<FromDuration>(ToDuration(1));
constexpr auto round_add = one > one.zero()
? one - FromDuration(1)
: one.zero();
return std::chrono::duration_cast<ToDuration>(d + round_add);
}
/** /**
* Convert the given timeout specification to a milliseconds integer, * Convert the given timeout specification to a milliseconds integer,
* to be used by functions like poll() and epoll_wait(). Any negative * to be used by functions like poll() and epoll_wait(). Any negative
@ -171,8 +183,7 @@ static constexpr int
ExportTimeoutMS(Event::Duration timeout) ExportTimeoutMS(Event::Duration timeout)
{ {
return timeout >= timeout.zero() return timeout >= timeout.zero()
/* round up (+1) to avoid unnecessary wakeups */ ? int(duration_cast_round_up<std::chrono::milliseconds>(timeout).count())
? int(std::chrono::duration_cast<std::chrono::milliseconds>(timeout).count()) + 1
: -1; : -1;
} }