;; Keep dosync body free of side-effects:
(defn my-thread-unsafe-fn [important-ref]
(let [start-work (ref false)]
(dosync
(when (not @important-ref)
;"If a conflict occurs between 2 transactions
;trying to modify the same reference,
;one of them will be retried."
;http://clojure.org/concurrent_programming
(ref-set important-ref true)
(ref-set start-work true)))
(when @start-work
;launch side-effects here
)))
Source
clojure/core.clj:4445
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(defmacro dosync
"Runs the exprs (in an implicit do) in a transaction that encompasses
exprs and any nested calls. Starts a transaction if none is already
running on this thread. Any uncaught exception will abort the
transaction and flow out of dosync. The exprs may be run more than
once, but any effects on Refs will be atomic."
{:added "1.0"}
[& exprs]
`(sync nil ~@exprs))
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