operating-system - 为什么 xv6 调度程序在每个循环开始时调用 sti()？

Question

配套书说

The reason to enable interrupts periodically on an idling CPU is that there might be no RUNNABLE process because processes (e.g., the shell) are waiting for I/O; if the scheduler left interrupts disabled all the time, the I/O would never arrive.

但我认为我们只需要在外部 for 循环之前调用 sti() 一次，因为每次我们释放 ptable.lock 时，中断都会再次启用。

Answer 1

schedule() 调用时可能会禁用中断，在这种情况下释放 ptable 自旋锁不会重新启用它们。