On 3 April 2014 00:11, Sven Van Caekenberghe <s...@stfx.eu> wrote: > Hi, > > Is it possible to have a simple lock-free atomic counter in Pharo 3.0 ? > > nextId > ^ idCounter := idCounter + 1 > > Or is it still possible that two process entering this code can mess > things up ? > > #+ is a message send. So technically, if you will be interrupted at the point of returning a result from it, then somebody else could run #nextId without notice, as result you will get 2 processes returning same value from #nextId. (and increasing numbers of concurrent processes will produce even more surprising results :)
> I vaguely remember a discussion about that long ago... > > assignment is atomic.. the one which i use in atomic queue impl., but it is hidden, undocumented VM implementation detail :) e.g.: oldA := a. a := newA. .. actually can be any series of it, as long as nothing else there (no message sends) x:= a. y:=b. z := c. w := e. will be performed atomically. > TIA, > > Sven > -- Best regards, Igor Stasenko.
