Linux 0.12: Task Switching 条件

Quoted from Inter Intel 80386 Programmer's Reference Manual

 

The 80386 switches execution to another task in any of four cases:

遇到以下四种情况，发生任务切换

 

  1.  The current task executes a JMP or CALL that refers to a TSS  descriptor.  2.  The current task executes a JMP or CALL that refers to a task gate.  3.  An interrupt or exception vectors to a task gate in the IDT.  4.  The current task executes an IRET when the NT flag is set.

To cause a task switch, a JMP or CALL instruction can refer either to a TSS descriptor or to a task gate. 

The effect is the same in either case: the 80386 switches to the indicated task

也就是说，想要发生任务切换，就要去访问TSS描述符 或者 访问 任务门。 这个任务门可以放到 IDT中。