From: "jsc (Justin Collins)" <redmine@...>
Date: 2014-01-02T15:53:31+09:00
Subject: [ruby-core:59464] [ruby-trunk - Bug #9342] [PATCH] SizedQueue#clear	does not notify waiting threads in Ruby 1.9.3


Issue #9342 has been updated by jsc (Justin Collins).

File 0002-Wake-waiting-threads-when-SizedQueue-clear-is-called-2.0.patch added

Looks like this is also a problem in 2.0.0, although the implementation is a little different. Attaching patch for 2.0.0 too although it's probably clear.
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Bug #9342: [PATCH] SizedQueue#clear does not notify waiting threads in Ruby 1.9.3
https://bugs.ruby-lang.org/issues/9342#change-44017

Author: jsc (Justin Collins)
Status: Open
Priority: Normal
Assignee: 
Category: 
Target version: 
ruby -v: ruby 1.9.3p484 (2013-11-22 revision 43786) [x86_64-darwin11.4.2]
Backport: 1.9.3: UNKNOWN, 2.0.0: UNKNOWN, 2.1: UNKNOWN


In Ruby 1.9.3, when SizedQueue#clear is called, it empties the queue but does not notify waiting threads that the queue is empty. This typically leads to deadlock when the queue is full.

For example:

sq = SizedQueue.new(1)
sq << 1  # Fill queue

t1 = Thread.new do
  sq << 1  # Attempt to add another item to queue, fail and go to sleep waiting
end

t2 = Thread.new do
  Thread.pass
  sq.clear
end

t2.join # Empty queue
t1.join # Deadlock, t1 continues to sleep



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