Definition and difference between Hardware interrupt, Software Interrupt, Exception, Trap and Signals?
Answer:
Interrupts can be categorized into two groups which are asynchronous interrupts (aka interrupt, hardware interrupt) and synchronous interrupts (aka exception). The former may arrive anytime, typically IO interrupts, the latter may only arrive after the execution of an instruction, for example when the cpu try to divide a number by 0 or a page fault. So that’s the difference between interrupts and exception.
Exception includes trap, fault, abort.
A trap is a kind of exceptions, whose main purpose is for debugging (eg. notify the debugger that an instruction has been reached).
A software interrupt (aka Programmed Exceptions) occur at the request of the programmer. They are used to implement system calls. Software interrupt is a considered to be an exception (because they are synchronous). Note that as far as Linux is concerned, software interrupt are handled by the CPU as trap so you might see somewhere else that system calls are implemented by trap.
Signals (or at least UNIX signals) are part of the inter process communication (IPC). They are just like asynchronous message that one process can send to another one. So I would not consider them to be interrupt or exception.
陷阱：由 trap 指令引起，恢复后 CPU 执行下一条指令(Debug point, system call)
中断：由硬件电平引起，恢复后 CPU 执行下一条指令
异常：由软件指令引起，恢复后 CPU 重新执行该条指令(Divide a number by 0 or a page fault)
中断和异常有个比较大的共同点就是"不可预知性"，所以是被迫的；而陷阱有"有意为之"的含义
中断、异常和陷阱产生时都需要切换当前进程上下文进入中断处理程序(IDT table).