thin.patch

--- a/lib/thin/server.rb	2014-01-06 23:53:11.517120396 +0100
+++ b/lib/thin/server.rb	2014-01-06 23:54:18.549990835 +0100
@@ -207,6 +207,17 @@
     def running?
       @backend.running?
     end
+
+    def log_backtrace
+      Thread.list.each do |thread|
+        log "Thread TID-#{thread.object_id.to_s(36)} #{thread['label']}"
+        if thread.backtrace
+          log thread.backtrace.join("\n")
+        else
+          log "<no backtrace available>"
+        end
+      end
+    end
     
     protected
       # Register signals:
@@ -215,6 +226,7 @@
       def setup_signals
         trap('INT')  { stop! }
         trap('TERM') { stop! }
+        trap('USR2') { log_backtrace }
         unless Thin.win?
           trap('QUIT') { stop }
           trap('HUP')  { restart }