From: Motohiro KOSAKI <kosaki.motohiro@...>
Date: 2011-05-18T20:36:02+09:00
Subject: [ruby-core:36313] [Ruby 1.9 - Bug #4283] Timeout.timeout may cause application exit unintetionally


Issue #4283 has been updated by Motohiro KOSAKI.


I've committed timeout-race-fix.patch as r31623 and I confirmed it fixes Charles's load test (ie https://github.com/jruby/jruby/blob/master/test/load/load_timeout.rb). I know it doesn't fix Ctrl-C issue. However I think we can discuss it separately. 
----------------------------------------
Bug #4283: Timeout.timeout may cause application exit unintetionally
http://redmine.ruby-lang.org/issues/4283

Author: Motohiro KOSAKI
Status: Closed
Priority: Normal
Assignee: Yukihiro Matsumoto
Category: lib
Target version: 1.9.3
ruby -v: ruby 1.9.3dev (2010-12-22 trunk 30291) [x86_64-linux]


=begin
 This issue was discovered during [Bug#4266] discussion.
 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.
=end



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