Piping seque into seque can deadlock

Description

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

1 2 3 (let [xs (seque (range 150000)) ys (seque (filter odd? xs))] (apply + ys))

Cause: 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.

Approach: Use (release-pending-sends) in seque's drain function to avoid the deadlock when a seque is fed into another seque.

Patch: clj-823-v1.patch

Screened by: Alex Miller

Environment

Windows 7; JVM 1.6; Clojure 1.3 beta 1

Status

Assignee

Unassigned

Reporter

Greg Chapman

Labels

None

Approval

Ok

Patch

Code and Test

Fix versions

Affects versions

Release 1.3

Priority

Minor
Configure