[ruby-core:30137] [Bug #2629](Rejected) ConditionVariable#wait(mutex, timeout) should return whether the condition was signalled, not the waited time

Issue #2629 has been updated by Yusuke Endoh.

Status changed from Open to Rejected

Hi, Hongli

Even if there is no return value, you can detect the timeout
*without guessing* by the following:

  mutex.synchronize do
    t = Time.now + x
    until @quit
      t2 = Time.now
      cv.wait(mutex, t - t2) if t > t2
      break if @quit
      if Time.now > t
        t += x
        # cleanup code
      end
    end
    # stop the loop
  end

I recommend this code because it is robust against spurious
wakeup.


I think the feature you requested can be used to make the
code more efficient, like the following:

  mutex.synchronize do
    t = Time.now + x
    until @quit
      t2 = Time.now
      timeout = t <= t2 || cv.wait(mutex, t - t2)
      break if @quit  # (A)
      if timeout
        t += x
        # cleanup code
      end
    end
    # stop the loop
  end

But, the feature is not mandatory, and is even prone to misuse
(the check (A) is very easy to forget).

In addition, Tanaka Akira, who has added the timeout feature
to CV#wait, rejected the feature.

Consequently, I close this ticket.  Sorry for decision against
your exception, and also sorry for not deciding sooner.

-- 
Yusuke Endoh <[e-mail]>
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