Hi,
Am 26.04.2011 um 22:33 schrieb Zlatko Josic:
> Is this scenario posible :
>
> (def test-map (ref {}))
>
> (def test-map2 (ref {}))
>
> (defn process
> [map1 map2]
> (cond
> (and (empty? @map1) (empty? @map2))
> (dosync
> ((alter map1 assoc key1 value1)
> (alter map2 assoc key2 value2)
> .....
>
>
> Suppose the process method is called from many threads. Is it posible that
> one thread tests first condition (empty? @map1) and gets true
> than another thread comits its transaction wich puts values in both maps. Now
> first thread check second
> condition (empty? @map2) which is false.
Yes. This is perfectly possible. You have to wrap the whole cond in a dosync.
Otherwise it is not guaranteed that you see consistent values of map1 and map2.
Sincerely
Meikel
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