From f6180389d2a205bc655606d65c458b05fb55e44d Mon Sep 17 00:00:00 2001
From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Date: Fri, 11 Feb 2011 16:40:27 +0900
Subject: [PATCH] timeout fix

Current timeout is racy.

Now, timeout module has following code.
-------------------------------------------------------------------------------
  def timeout()
    begin
      x = Thread.current
      y = Thread.start {
        begin
          sleep sec
        rescue => e
          x.raise e
        else
          x.raise exception, "execution expired" if x.alive?
        end
      }
      return yield(sec)
    rescue exception => e
      raise Error, e.message, e.backtrace
    ensure
      if y and y.alive?
        // (1)
        y.kill
        y.join # make sure y is dead.
      end
    end
  end
-------------------------------------------------------------------------------

Then, A following race can occur.

  CPU0(thread x)                    CPU1(thread y)         remark
---------------------------------------------------------------------------
  begin
  Thread.start
                                     sleep sec
  evaluate [user-defined-block]
  y.alive?                                                  return true
                                     wakeup from sleep
                                     x.raise

Now, x is running at (1). Then ExitException which y raised can't be
handled
above rescue block. Then eventually, ExitException leak to caller and
makes
application exit.

This patch fixes it.
---
 lib/timeout.rb |   32 +++++++++++++++++---------------
 1 files changed, 17 insertions(+), 15 deletions(-)

diff --git a/lib/timeout.rb b/lib/timeout.rb
index 297b769..aa0e757 100644
--- a/lib/timeout.rb
+++ b/lib/timeout.rb
@@ -44,17 +44,24 @@ module Timeout
     return yield(sec) if sec == nil or sec.zero?
     exception = klass || Class.new(ExitException)
     begin
-      x = Thread.current
-      y = Thread.start {
-        begin
-          sleep sec
-        rescue => e
-          x.raise e
-        else
-          x.raise exception, "execution expired" if x.alive?
+      begin
+        x = Thread.current
+        y = Thread.start {
+          begin
+            sleep sec
+          rescue => e
+            x.raise e
+          else
+            x.raise exception, "execution expired"
+          end
+        }
+        return yield(sec)
+      ensure
+        if y
+          y.kill
+          y.join # make sure y is dead.
         end
-      }
-      return yield(sec)
+      end
     rescue exception => e
       rej = /\A#{Regexp.quote(__FILE__)}:#{__LINE__-4}\z/o
       (bt = e.backtrace).reject! {|m| rej =~ m}
@@ -66,11 +73,6 @@ module Timeout
       raise if klass            # if exception class is specified, it
                                 # would be expected outside.
       raise Error, e.message, e.backtrace
-    ensure
-      if y and y.alive?
-        y.kill
-        y.join # make sure y is dead.
-      end
     end
   end
 
-- 
1.6.5.2