Fixe a race confition in NxWM::CCalibration

3 files changed, 49 insertions, 14 deletions

diff --git a/NxWidgets/ChangeLog.txt b/NxWidgets/ChangeLog.txt
index c72d20782..46eb06a08 100644
--- a/NxWidgets/ChangeLog.txt
+++ b/NxWidgets/ChangeLog.txt
@@ -354,3 +354,7 @@
    need to minimize the icon size a bit.  From Ken Pettit (2013-5-11).
 *  NxWidgets/nxwm/src/glyph_mediaplayer.cxx:  Smaller version of the
    media player glyph.  From Ken Pettit (2013-5-12).
+*  NxWidgets/nxwm/include/ccalibration.hxx and src/ccalibration.cxx:
+   Fix a race condition that would cause the calibration screen
+   to fail to come up when its icon was touched (From Ken Pettit,
+   2013-5-12).
diff --git a/NxWidgets/nxwm/include/ccalibration.hxx b/NxWidgets/nxwm/include/ccalibration.hxx
index a54a35bf7..f114a19a2 100644
--- a/NxWidgets/nxwm/include/ccalibration.hxx
+++ b/NxWidgets/nxwm/include/ccalibration.hxx
@@ -1,7 +1,7 @@
 /****************************************************************************
  * NxWidgets/nxwm/include/ccalibration.hxx
  *
- *   Copyright (C) 2012 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2012-2013 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <gnutt@nuttx.org>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -175,22 +175,45 @@ namespace NxWM
 
     /**
      *  Return true if the calibration thread is running normally.  There are
-     *  lots of potential race conditions.  Let's hope that things are running
-     *  orderly and we that we do not have to concern ourself with them
+     *  lots of potential race conditions.  There are also two ambiguous
+     *  states:
+     *
+     *  1) The thread may have been started but not yet running
+     *     (CALTHREAD_STARTED), or the
+     *  2) The thread may been requested to terminate, but has not yet
+     *     terminated (CALTHREAD_STOPREQUESTED)
+     *
+     *  Both of those states will cause isRunning() to return false.
      *
      * @return True if the calibration thread is runnning normally.
      */
 
     inline bool isRunning(void) const
       {
-        // What if the boundary states CALTHREAD_STARTED and CALTHREAD_STOPREQUESTED?
- 
         return (m_calthread ==  CALTHREAD_RUNNING ||
                 m_calthread ==  CALTHREAD_HIDE ||
                 m_calthread ==  CALTHREAD_SHOW);
       }
 
     /**
+     *  Return true if the calibration thread is has been started and has not
+     *  yet terminated.  There is a potential race condition here when the
+     *  thread has been requested to terminate, but has not yet terminated
+     *  (CALTHREAD_STOPREQUESTED).  isStarted() will return false in that case.
+     *
+     * @return True if the calibration thread has been started and/or is
+     *  running normally.
+     */
+
+    inline bool isStarted(void) const
+      {
+        return (m_calthread ==  CALTHREAD_STARTED ||
+                m_calthread ==  CALTHREAD_RUNNING ||
+                m_calthread ==  CALTHREAD_HIDE ||
+                m_calthread ==  CALTHREAD_SHOW);
+      }
+
+    /**
      * The calibration thread.  This is the entry point of a thread that provides the
      * calibration displays, waits for input, and collects calibration data.
      *
diff --git a/NxWidgets/nxwm/src/ccalibration.cxx b/NxWidgets/nxwm/src/ccalibration.cxx
index 32aeb5ee6..04233d5ef 100644
--- a/NxWidgets/nxwm/src/ccalibration.cxx
+++ b/NxWidgets/nxwm/src/ccalibration.cxx
@@ -1,7 +1,7 @@
 /****************************************************************************
  * NxWidgets/nxwm/src/ccalibration.cxx
  *
- *   Copyright (C) 2012 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2012-2013 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <gnutt@nuttx.org>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -247,26 +247,34 @@ void CCalibration::hide(void)
 
 void CCalibration::redraw(void)
 {
-  gvdbg("Entry\n");
+  uint8_t waitcount = 0;
 
-  // Is the calibration thread running?  We might have to restart it if
-  // we have completed the calibration early but are being brought to
-  // top of the display again
+  gvdbg("Entry\n");
 
-  // Is the calibration thread running?
+  // Is the calibration thread still running?  We might have to restart
+  // it if we have completed the calibration early but are being brought
+  // to top of the display again
 
-  if (!isRunning())
+  if (!isStarted())
     {
       gvdbg("Starting calibration: m_calthread=%d\n", (int)m_calthread);
       (void)startCalibration(CALTHREAD_SHOW);
     }
 
+  // Is the calibration thread running? If not, then wait until it is.
+
+  while (!isRunning() && (++waitcount < 10))
+    {
+      usleep(500);
+    }
+
   // The calibration thread is running.  Make sure that is is not
   // already processing a redraw
 
-  else if (m_calthread != CALTHREAD_SHOW)
+  if (m_calthread != CALTHREAD_SHOW)
     {
-      // Ask the calibration thread to restart the calibration and redraw the display
+      // Ask the calibration thread to restart the calibration and redraw
+      // the display
 
       m_calthread = CALTHREAD_SHOW;
       (void)pthread_kill(m_thread, CONFIG_NXWM_CALIBRATION_SIGNO);