PiOS posix scheduler - added simple docu about scheduler work

git-svn-id: svn://svn.openpilot.org/OpenPilot/trunk@1032 ebee16cc-31ac-478f-84a7-5cbb03baadba

flight/PiOS.posix/posix/Libraries/FreeRTOS/Source/portable/GCC/Posix/corvuscorax/scheduler.txt

@@ -0,0 +1,42 @@
+thread initial START:
+
+master gives up running mutex
+master waits for sentinel set
+master akquires running mutex
+
+thread akquires RUNNING_MUTEX
+threads sets sentinel
+thread suspends itself
+
+
+
+thread SUSPEND:
+
+thread gives up RUNNING_MUTEX
+thread waits for sig_resume
+thread akquires RUNNING_MUTEX
+thread runs
+
+
+thread END:
+
+if other:
+delete the other thread
+if self:
+thread gives up RUNNING_MUTEX
+thread sends sig_resume to new active thread
+thread self kills
+
+
+thread YIELD
+thread sends sig_resume to new active thread
+thread suspends itself
+
+
+time tick yield
+tick handler sends SUSPEND to running thread
+tick handler akquires RUNNING_MUTEX
+tick handler sends sig_resume to new active thread
+tock handler gives up RUNNING_MUTEX
+tick handler ends
+