Just checking my understanding. It seems to me that it is not possible for Clojure to remove the possibility of writing code that has race conditions. I could write code in which two threads each change the value of the same Ref inside a transaction. Let's say the Ref starts with a value of 2, one transaction adds 3 and the other multiplies by 4. Depending on which thread runs first, after they both complete the value of the Ref will either be (2 + 3) * 4 = 20 or (2 * 4) + 3 = 11. Of course as the developer I could decide to use an Agent instead of a Ref and then send actions to the Agent in the order in which I want them to run to fix this problem. But Clojure itself can't prevent this situation. The developer has to recognize the potential race condition and write the code in a way to avoid it. Sound correct?
Does Clojure STM eliminate the possibility of deadlock? When two transactions have a contention for the same Ref, Clojure gives preference to the transaction that has been running the longest (unless it has only been running for a very short amount of time - see bargeTimeElapsed in LockingTransaction.java). Is that alone enough to guarantee that a deadlock over Refs cannot occur? The transaction that has been running the longest may never finish, going into an infinite loop. Other transactions that contend for the same Refs will continue retrying until they hit the 10,000 retry limit and then an exception will be thrown, so I supposed technically that isn't deadlock. -- R. Mark Volkmann Object Computing, Inc. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en -~----------~----~----~----~------~----~------~--~---
