Minor updates for PIC32 USB device driver bugs

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@4497 42af7a65-404d-4744-a932-0658087f49c3

configs/pic32-starterkit/README.txt

@@ -1171,4 +1171,30 @@ Where <subdir> is one of the following:
     little testing I have done with it, it appears functional.  But the
     logic has not been stressed and there could still be lurking issues.
  
+    Update. The following was added to the top-level TODO list:
 
+    Title:       PIC32 USB DRIVER DOES NOT WORK WITH MASS STORAGE CLASS
+    Description: The PIC32 USB driver either crashes or hangs when used with
+                 the mass storage class when trying to write files to the target
+                 storage device.  This usually works with debug on, but does not
+                 work with debug OFF (implying some race condition?)
+
+                 Here are some details of what I see in debugging:
+
+                 1. The USB MSC device completes processing of a read request
+                    and returns the read request to the driver.
+                 2. Before the MSC device can even begin the wait for the next
+                    driver, many packets come in at interrupt level.  The MSC
+                    device goes to sleep (on pthread_cond_wait) with all of the
+                    read buffers ready (16 in my test case).
+                 3. The pthread_cond_wait() does not wake up.  This implies
+                    a problem with pthread_con_wait(?).  But in other cases,
+                    the MSC device does wake up, but then immediately crashes
+                    because its stack is bad.
+                 4. If I force the pthread_cond_wait to wake up (by using
+                    pthread_cond_timedwait instead), then the thread wakes
+                    up and crashes with a bad stack.
+
+                 So far, I have no clue why this is failing.
+    Status:      Open
+    Priority:    High