Linux 0.12: Task Switching 條件

Quoted from Inter Intel 80386 Programmer's Reference Manual

 

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

遇到以下四種情況，發生任務切換

 

  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

也就是說，想要發生任務切換，就要去訪問TSS描述符 或者 訪問 任務門。 這個任務門可以放到 IDT中。