fixed stale status bug and better error handling

solved duplicate event processing

usr/lib/python2.7/dist-packages/sdwdate_gui/sdwdate_gui.py

@@ -83,8 +83,7 @@ def __init__(self, parent=None):
         if os.path.exists(self.status_path):
             ## Read status when GUI is loaded.
             self.status_changed()
-            self.watcher = watcher([self.status_path])
-            self.watcher.fileChanged.connect(self.status_changed)
+            self.watch_file()
         else:
             self.setIcon(QtGui.QIcon('/usr/share/icons/oxygen/16x16/status/dialog-error.png'))
             error_msg = '''<b>sdwdate is not running</b><br>
@@ -141,12 +140,13 @@ def update_tip(self):
                 self.show_message('update')
 
     def status_changed(self):
-        ## Prevent race condition.
-        ## Likely due to the issue below.
-        time.sleep(0.01)
-
-        with open(self.status_path, 'rb') as f:
-            status = pickle.load(f)
+        ## When the file is quickly rewritten by another operation, reading
+        ## would fail. TOCTOU
+        try:
+            with open(self.status_path, 'rb') as f:
+                status = pickle.load(f)
+        except:
+            return
 
         self.setIcon(QtGui.QIcon(status['icon']))
         ## Remove double quotes from message as they would be interpreted as
@@ -164,10 +164,16 @@ def status_changed(self):
             self.update.update_tip.emit()
         self.previous_message = self.message
 
-    def watch_folder(self):
+    def watch_file(self):
         self.watcher = watcher([self.status_path])
         self.watcher.fileChanged.connect(self.status_changed)
 
+    def watch_folder(self):
+        if os.path.exists(self.status_path):
+            self.watcher_2.removePath(self.path)
+            self.status_changed()
+            self.watch_file()
+
 
 def show_log():
     show_konsole = ('konsole --hold --hide-menubar --hide-tabbar ' +

usr/share/sdwdate-gui/unit-test/fuzzer

@@ -0,0 +1,33 @@
+#!/bin/bash
+
+set -x
+set -e
+
+counter=0
+
+while true ; do
+   for icon in /usr/share/icons/sdwdate-gui/* ; do
+      msg="$(cat /proc/sys/kernel/random/uuid)"
+
+      echo "(dp0
+S'message'
+p1
+S\"$msg\"
+p2
+sS'icon'
+p3
+S'$icon'
+p4
+s." > /var/run/sdwdate/status
+
+      counter=$(( counter + 1 ))
+      if [ "$counter" -ge 1000 ]; then
+         do_break=true
+      fi
+
+      #sleep 1
+   done
+   if [ "$do_break" = "true" ]; then
+      break
+   fi
+done