[ruby/timeout] Handle Timeout + fork and add test for it

https://github.com/ruby/timeout/commit/4baee63b9b

lib/timeout.rb

@@ -95,31 +95,38 @@ module Timeout
   end
   private_constant :Request
 
-  def self.ensure_timeout_thread_created
-    unless @timeout_thread
-      TIMEOUT_THREAD_MUTEX.synchronize do
-        @timeout_thread ||= Thread.new do
-          requests = []
-          while true
-            until QUEUE.empty? and !requests.empty? # wait to have at least one request
-              req = QUEUE.pop
-              requests << req unless req.done?
-            end
-            closest_deadline = requests.min_by(&:deadline).deadline
+  def self.create_timeout_thread
+    Thread.new do
+      requests = []
+      while true
+        until QUEUE.empty? and !requests.empty? # wait to have at least one request
+          req = QUEUE.pop
+          requests << req unless req.done?
+        end
+        closest_deadline = requests.min_by(&:deadline).deadline
 
-            now = 0.0
-            QUEUE_MUTEX.synchronize do
-              while (now = Process.clock_gettime(Process::CLOCK_MONOTONIC)) < closest_deadline and QUEUE.empty?
-                CONDVAR.wait(QUEUE_MUTEX, closest_deadline - now)
-              end
-            end
-
-            requests.each do |req|
-              req.interrupt if req.expired?(now)
-            end
-            requests.reject!(&:done?)
+        now = 0.0
+        QUEUE_MUTEX.synchronize do
+          while (now = Process.clock_gettime(Process::CLOCK_MONOTONIC)) < closest_deadline and QUEUE.empty?
+            CONDVAR.wait(QUEUE_MUTEX, closest_deadline - now)
           end
         end
+
+        requests.each do |req|
+          req.interrupt if req.expired?(now)
+        end
+        requests.reject!(&:done?)
+      end
+    end
+  end
+  private_class_method :create_timeout_thread
+
+  def self.ensure_timeout_thread_created
+    unless @timeout_thread and @timeout_thread.alive?
+      TIMEOUT_THREAD_MUTEX.synchronize do
+        unless @timeout_thread and @timeout_thread.alive?
+          @timeout_thread = create_timeout_thread
+        end
       end
     end
   end

test/test_timeout.rb

@@ -139,4 +139,24 @@ class TestTimeout < Test::Unit::TestCase
     }
     assert(ok, bug11344)
   end
+
+  def test_fork
+    omit 'fork not supported' unless Process.respond_to?(:fork)
+    r, w = IO.pipe
+    pid = fork do
+      r.close
+      begin
+        r = Timeout.timeout(0.01) { sleep 5 }
+        w.write r.inspect
+      rescue Timeout::Error
+        w.write 'timeout'
+      ensure
+        w.close
+      end
+    end
+    w.close
+    Process.wait pid
+    assert_equal 'timeout', r.read
+    r.close
+  end
 end