Re: [go-nuts] Sync.wait()?

[Jesper Louis Andersen]

There are two Wait() methods in the sync package. One is on the type Cond
and one is on the type WaitGroup.

Assuming you mean waitgroup, the code uses the runtime call Semacquire
which is a semaphore lock. In that case, you are not looping anymore, but
waiting until said semaphore is released. It is released if a call to .Add
reaches 0 (Note that .Done is Add(-1)).

Assuming you mean Cond, the code uses the runtime notify list primitive to
park the goroutine until either Signal or Broadcast is called at which
point execution continues.

If this doesn't answer your question, please do not hesitate to elaborate
what your concern is.


On Mon, Feb 10, 2020 at 6:12 PM Joe McGuckin  wrote:

> Various sources say wait() waits until the internal counter reaches zero.
> Does it cause a real pause (e.g.: control passing to another goroutine?)
> Looking at the code, it just seems to loop endlessly waiting for the
> counter to reach zero. Is that somehow optimized away? Sitting in a tight
> loop waiting for a bunch of goroutines to exit seems like a waste of
> machine cycles...
>
> Joe
>
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> .
>


-- 
J.

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[go-nuts] Sync.wait()?

[Joe McGuckin]

Various sources say wait() waits until the internal counter reaches zero. 
Does it cause a real pause (e.g.: control passing to another goroutine?) 
Looking at the code, it just seems to loop endlessly waiting for the 
counter to reach zero. Is that somehow optimized away? Sitting in a tight 
loop waiting for a bunch of goroutines to exit seems like a waste of 
machine cycles...

Joe

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