資料來源 : Free On-Line Dictionary of Computing

priority inversion
     
         The state of a concurrent system where a high
        priority task is waiting for a low priority task which is
        waiting for a medium priority task.  The system may become
        unstable and {crash} under these circumstances.
     
        In an {operating system} that uses multiple tasks, each task
        (or {context}) may be given a priority.  These priorities help
        the {scheduler} decide which task to run next.  Consider
        tasks, L, M, and H, with priorities Low, Medium, and High.  M
        is running and H is blocked waiting for some resource that is
        held by L.  So long as any task with a priority higher than L
        is runable, it will prevent task L, and thus task H, from
        running.
     
        Priority inversion is generally considered either as a
        high-level design failure or an implementation issue to be
        taken into account depending on who is talking.  Most
        operating systems have methods in place to prevent or take
        inversion into account.  {Priority inheritance} is one method.
     
        The most public instance of priority inversion is the repeated
        'fail-safe' rebooting of the {Mars Pathfinder
       
     (http://research.microsoft.com/~mbj/Mars_Pathfinder/Mars_Pathfinder.html)}.
        base station ('Sagan Memorial Station').
     
        (2003-06-04)