Cleanup state for children that die during reexec

lib/einhorn.rb

@@ -130,11 +130,29 @@ def self.update_state(store, store_name, old_state)
         message << "upgraded :reloading_for_preload_upgrade to :reloading_for_upgrade"
       end
 
-      # For a period, we created children entries for state_passers,
-      # but we don't want that (in particular, it probably died before
-      # we could setup our SIGCHLD handler
       if updated_state[:children]
+        # For a period, we created children entries for state_passers,
+        # but we don't want that (in particular, it probably died
+        # before we could setup our SIGCHLD handler
         updated_state[:children].delete_if {|k, v| v[:type] == :state_passer}
+
+        # Depending on what is passed for --reexec-as, it's possible
+        # that the process received a SIGCHLD while something other
+        # than einhorn was the active executable. If that happened,
+        # einhorn might not know about a dead child, so let's check
+        # them all
+        dead = []
+        updated_state[:children].each do |pid, v|
+          begin
+            pid = Process.wait(pid, Process::WNOHANG)
+            dead << pid if pid
+          rescue Errno::ECHILD
+            dead << pid
+          end
+        end
+        Einhorn::Event::Timer.open(0) do
+          dead.each {|pid| Einhorn::Command.mourn(pid)}
+        end
       end
     end