Re: [boost] [boost thread rework] New version uploaded to BoostVault

From: Matt Hurd (matt.hurd_at_[hidden])
Date: 2005-09-03 09:21:38

> John Maddock wrote:
<snip>

> Cons:
> * If the functor takes a long time to execute, and there are multiple
> threads racing to call-once, then the wait will be less efficient than a
> mutex, this should be a very rare occurance though.

Neat.  Though , if f was longer than short, and there was contention,
a lot of wasted cycles could occur.

This leads to the thought that this spinning approach would suffer
from a priority problem if sufficient waiting threads, one on a single
cpu context, were at a higher priority than the initialising item. 
This would cause a virtual deadlock, a term I just made up ;-) 
pthread32's initial implementation was similar.

Your atomic approach is the right approach I think.  A suitable wait
list approach in the "already initializing" section with subsequent
processing after initialisation is complete should cure it and keep
the essence of the fast approach but make it a fair bit more
complicated.

matt.