Update TODO list

TODO

@@ -22,10 +22,10 @@ nuttx/:
  (16)  Network (net/, drivers/net)
   (4)  USB (drivers/usbdev, drivers/usbhost)
   (0)  Other drivers (drivers/)
- (13)  Libraries (libc/, libm/)
+ (14)  Libraries (libc/, libm/)
  (10)  File system/Generic drivers (fs/, drivers/)
  (10)  Graphics Subsystem (graphics/)
-  (2)  Build system / Toolchains
+  (3)  Build system / Toolchains
   (3)  Linux/Cywgin simulation (arch/sim)
   (4)  ARM (arch/arm/)
 
@@ -1740,6 +1740,52 @@ o Libraries (libc/, libm/)
   Status:      Open
   Priority:    Low
 
+  Title:       printf()/flush() Cancellation Point Problems
+  Description: printf() calls flush() which, in turn calls write().  write()
+               is a cancellation point and both print() and flush() are
+               permitted to be cancellation points according to
+               OpenGroup.org.
+
+               However, calling write(), albeit indirectly from printf()
+               does not make it a "well behaved" cancellation point.  When
+               write() exists, then the task or thread may be terminated
+               and printf() will leave the library semeaphore locked,
+               causing hang for the next task that calls printf().
+
+               There are basically three problems here.  Resolution of
+               any of these problems:
+
+               1. It is optional if printf is a cancellation point.  Because
+                  it calls write() (indirectly), it is essentially a
+                  cancellation point.  But it could be possible to generate
+                  a special interface, say nx_write() that behaves like
+                  write() but is not a cancellation point.  This function
+                  would have to be accessible from user space for the
+                  PROTECTED and KERNEL build.
+
+               2. pthreads maintain of list of all mutexes that they hold.
+                  These are handling according to OpenGroup.org when the
+                  pthread exits holding the mutex.  There is nothing
+                  comparable for tasks and semaphores, there is no list of
+                  semaphores held for each tasks or pthreads and there is
+                  no logic to deal with semaphores held when the task or
+                  pthread exits.
+
+               3. NuttX supports nested cancellation points:  A function
+                  that is a cancellation point can call another function
+                  that is also a cancellation point.  The cancellation will
+                  not occur until the final nested cancellation point
+                  exits.  So in the case of printf, if it were to be a
+                  cancellation point, then the actual action exit would not
+                  occur until printf() frees all semaphores and exits.
+                  Unfortunately, printf() is a user space interface and the
+                  cancellation interfaces are internal to the OS and would
+                  not be available to printf() in the PROTECTED or KERNEL
+                  build modes.
+  Status:      Open
+  Priority:    Medium-high.  Anything that can result in a hang is
+               automatically pretty high priority.
+
 o File system / Generic drivers (fs/, drivers/)
   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
@@ -2161,6 +2207,12 @@ o Build system
                to all Makefiles.  It has not yet been confirmed that this fix
                eliminates the dependency issue or not.
 
+  Title:      DEPENDENCIES OBJECT SUB-DIRECTORIES
+  Descripton: Dependencies do not work in directories that keep binaries in
+              a sub-directory like bin, ubin, kbin.
+  Status:     Open
+  Priority:   Medium-Low.  Definitely a build issue once in awhile.
+
 o Other drivers (drivers/)
   ^^^^^^^^^^^^^^^^^^^^^^^^