On Thu, 3 Apr 2014, Igor Stasenko wrote:
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
If #+ is compiled to bytecode 176, and both the receiver and the argument
are SmallIntegers, then it's not a message send, so the operation is
atomic.
Levente
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.
