safe_basic_coroutine_class.txt

safe basic controller api:
1. create
2. start
3. yield
4. resume <=> ÓÚstart
5. stop
 
basic data structure:
1. caller running stack information
2. callee coroutine running stack information
3. stack context coroutine running stack context
 
safe basic data structure:
1. busy status (spin lock)
2. running status
 
process:
|new [busy status => unlock, running status => INVALID]
|create(coroutine_context_callback) [running status => START]
|start          -@-> coroutine_context_callback                     [busy status => lock, running status => RUNNING]
                                 |
                                 V
|start/resume  <-@->        coroutine_run       ---------           [busy status => lock]
         ^                       |                      |
         |                       V                      |
|start/resume  <-@-            yield                    |           [busy status => unlock]
                                 |                      |
                                 V                      |
|               -@-> coroutine_context_callback <--------           [running status => FINISHED]
                                 |                      
                                 V
|start/resume  <-@-            yield                                [busy status => unlock, running status => STOP]
|delete