[ruby-core:28693] [Bug #2629] ConditionVariable#wait(mutex, timeout) should return whether the condition was signalled, not the waited time

Issue #2629 has been updated by Yusuke Endoh.

Category set to YARV
Target version set to 1.9.2

Hi, Hongli Lai

2010/1/22 Hongli Lai <[e-mail]>:
> ? There is a background thread which performs some cleaning function every x seconds. We also want to be able to tell the thread to clean now, or to exit (i.e. quitting its main loop so that we can join the thread). This thread waits on a condition variable for x seconds, and then checks whether there was a timeout on the wait, or whether the wait as signaled. In case of the former it will run the cleanup code. In case of the latter it'll check whether @quit is set, and then either stop the loop or run the cleanup code.

Could you show me a concrete code?
I guess it is more robust to always check @quit, regardless of whether
it was timed out or signaled.

I could be wrong because I'm not familiar with multi-thread programming,
but I doubt that it is potentially dangerous to depend on the reason of
wait termination.  Couldn't it cause race condition?

I have no idea about concrete race scenario, but there is a circumstance
where Java's Object#wait seems not to return the termination reason.


> The problem with 1.9.2dev's return value is that there is no way for me to detect whether the condition was signaled or whether the wait timed out.
> I can try to guess whether there was a timeout by checking whether the waited time is >= the timeout, but the return value doesn't allow me to do even that because it has seconds resolution. Right now I have to work around it by placing Time.now.to_f timers around the #wait call, so that I can measure the difference in time in miliseconds or microseconds.

FYI, ConditionVariable#wait returns self currently, for 1.8 compatibility.

-- 
Yusuke ENDOH <[e-mail]>
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