Clojure

Piping seque into seque can deadlock

Details

  • Type: Defect Defect
  • Status: Open Open
  • Priority: Minor Minor
  • Resolution: Unresolved
  • Affects Version/s: Release 1.3
  • Fix Version/s: None
  • Component/s: None
  • Labels:
    None
  • Environment:
    Windows 7; JVM 1.6; Clojure 1.3 beta 1
  • Approval:
    Vetted

Description

I'm not sure if this is a supported scenario, but the following deadlocks in Clojure 1.3:

(let [xs (seque (range 150000))
ys (seque (filter odd? xs))]
(apply + ys))

As I understand it, the problem is that ys' fill takes place on an agent thread, so when it calls xs' drain, the (send-off agt fill) does not immediately trigger xs' fill, but is instead put on the nested list to be performed when ys' agent returns. Unfortunately, ys' fill will eventually block trying to take from xs, and so it never returns and the pending send-offs are never sent. Wrapping the send-off in drain to:

(future (send-off agt fill))

is a simple (probably not optimal) way to fix the deadlock.

Activity

Stuart Halloway made changes -
Field Original Value New Value
Approval Triaged [ 10120 ]
Rich Hickey made changes -
Approval Triaged [ 10120 ] Vetted [ 10003 ]

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Dates

  • Created:
    Updated: