From 27674e4beb0391464fb97dcf15b884207789be2c Mon Sep 17 00:00:00 2001
From: Justin Collins <justin@presidentbeef.com>
Date: Wed, 1 Jan 2014 20:45:12 -0800
Subject: [PATCH] Wake waiting threads when SizedQueue#clear is called

---
 lib/thread.rb             | 16 ++++++++++++++++
 test/thread/test_queue.rb | 22 ++++++++++++++++++++++
 2 files changed, 38 insertions(+)

diff --git a/lib/thread.rb b/lib/thread.rb
index 58c4f6b..494a5b3 100644
--- a/lib/thread.rb
+++ b/lib/thread.rb
@@ -355,6 +355,22 @@ class SizedQueue < Queue
   def num_waiting
     @waiting.size + @queue_wait.size
   end
+
+  #
+  # Removes all objects from the queue and wakes waiting threads, if any.
+  #
+  def clear
+    @mutex.synchronize do
+      @que.clear
+      begin
+        until @queue_wait.empty?
+          @queue_wait.shift.wakeup
+        end
+      rescue ThreadError
+        retry
+      end
+    end
+  end
 end
 
 # Documentation comments:
diff --git a/test/thread/test_queue.rb b/test/thread/test_queue.rb
index b0ffe08..9d8d481 100644
--- a/test/thread/test_queue.rb
+++ b/test/thread/test_queue.rb
@@ -10,6 +10,28 @@ class TestQueue < Test::Unit::TestCase
     grind(5, 1000, 15, SizedQueue, 1000)
   end
 
+  def test_sized_queue_clear
+    # Fill queue, then test that SizedQueue#clear wakes up all waiting threads
+    sq = SizedQueue.new(2)
+    2.times { sq << 1 }
+
+    t1 = Thread.new do
+      sq << 1
+    end
+
+    t2 = Thread.new do
+      sq << 1
+    end
+
+    t3 = Thread.new do
+      Thread.pass
+      sq.clear
+    end
+
+    [t3, t2, t1].each(&:join)
+    assert_equal sq.length, 2
+  end
+
   def grind(num_threads, num_objects, num_iterations, klass, *args)
     from_workers = klass.new(*args)
     to_workers = klass.new(*args)
-- 
1.8.3.2