webrick: use monotonic clock for timeouts

The monotonic clock is immune to system time changes and
a better option for implementing timing comparisons.

* lib/webrick/utils.rb (TimeoutHandler): use monotonic clock
  (watch): ditto

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@56417 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,8 @@
+Fri Oct 14 10:48:37 2016  Eric Wong  <e@80x24.org>
+
+	* lib/webrick/utils.rb (TimeoutHandler): use monotonic clock
+	  (watch): ditto
+
 Thu Oct 13 19:41:32 2016  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* io.c (copy_stream_body): use IO to write to copy to duplex IO.

lib/webrick/utils.rb

@@ -134,7 +134,8 @@ module WEBrick
       # +time+:: Timeout in seconds
       # +exception+:: Exception to raise when timeout elapsed
       def TimeoutHandler.register(seconds, exception)
-        instance.register(Thread.current, Time.now + seconds, exception)
+        at = Process.clock_gettime(Process::CLOCK_MONOTONIC) + seconds
+        instance.register(Thread.current, at, exception)
       end
 
       ##
@@ -163,7 +164,7 @@ module WEBrick
         def watch
           to_interrupt = []
           while true
-            now = Time.now
+            now = Process.clock_gettime(Process::CLOCK_MONOTONIC)
             wakeup = nil
             to_interrupt.clear
             TimeoutMutex.synchronize{