Question

    +---------+               +---------------+               +---------+
--- | newproc | --- M.g0 ---> | schedule      | --- M.g0 ---> | execute |
    +---------+               +---------------+               +---------+
    |  wakep  |               |  runqget      |               |   gogo  |
    +---------+               +---------------+               +---------+
    |  startm |               |  globrunqget  |                    |
    +---------+               +---------------+                    |
                              |  findrunnable |                    |
                              +---------------+                    |
                                    ^                           G.stack
                                    |                              |
                                    |                              |
                                   M.g0                            |
                                    |                              |
                                    |                              v
                              +----------+                      +------+
                              | goexit1  | <------ M.g0 ------- | G.fn |
                              +----------+                      +------+
           ........ mexit ... |  goexit0 | 
                              +----------+

• schedule: 核心调度函数。检查状态，查找可用任务。
• execute: 任务执行函数。切换到用户栈，并执行用户函数。
• goexit: 任务结束函数。清理现场，重新进入调度循环。