From: Nobuyoshi Nakada <nobu@...>
Date: 2007-04-19T13:20:15+09:00
Subject: Re: Why does this code deadlock?

Hi,

At Wed, 18 Apr 2007 16:53:25 +0900,
Yukihiro Matsumoto wrote in [ruby-talk:248325]:
> |At Wed, 18 Apr 2007 08:34:03 +0900,
> |Bill Kelly wrote in [ruby-talk:248300]:
> |> require 'net/ftp'
> |> Thread.abort_on_exception = true
> |> ftp = Net::FTP.new('ftp.idsoftware.com')
> |  th = Thread.new {$SAFE=4; ftp.login('anonymous', 'abc@def.com')}
> |  Thread.critical = false
> |  p th.value
> 
> Who set Thread.critical?  It should be fixed, I think.

mon_acquire called from mon_enter fails because of
SecurityError, and leaves Thread.critical true.


Index: lib/monitor.rb
===================================================================
--- lib/monitor.rb	(revision 12191)
+++ lib/monitor.rb	(working copy)
@@ -106,12 +106,15 @@     def wait(timeout = nil)
       ensure
 	Thread.critical = true
-	if timer && timer.alive?
-	  Thread.kill(timer)
+	begin
+	  if timer && timer.alive?
+	    Thread.kill(timer)
+	  end
+	  if @waiters.include?(Thread.current)  # interrupted?
+	    @waiters.delete(Thread.current)
+	  end
+	  @monitor.instance_eval {mon_enter_for_cond(count)}
+	ensure
+	  Thread.critical = false
 	end
-	if @waiters.include?(Thread.current)  # interrupted?
-	  @waiters.delete(Thread.current)
-	end
-        @monitor.instance_eval {mon_enter_for_cond(count)}
-	Thread.critical = false
       end
     end
@@ -211,4 +214,5 @@   def mon_enter
     mon_acquire(@mon_entering_queue)
     @mon_count += 1
+  ensure
     Thread.critical = false
   end
@@ -300,6 +304,7 @@   def mon_exit_for_cond
     count = @mon_count
     @mon_count = 0
-    mon_release
     return count
+  ensure
+    mon_release
   end
 end


-- 
Nobu Nakada