原创 busybox ctrl+c不能终止进程(引用)

 2008-10-30 13:28  4710 2 2 分类: MCU/ 嵌入式

最近的一段时间中，发现在busybox下调试时，shell终端用ctrl+c不能终止掉正在运行的进程。参考了网上的一些网友的blog的解决方法以及自己的理解，这边把解决方法告诉大家。

Ctrl+C终止进程的流程是这样的：

Ctrl + C首先通过 /dev/ttyS0 (/dev/console)的driver，这个serial driver直接把这个控制字符送到n_tty的driver，n_tty负责search所有的控制字符。

当 ctrl+C 按下，

n_tty.c:
n_tty_receive_break() –> isig(SIGINT,tty) –> kill_pg(SIGINT, tty->pgrp)

signal.c: kill_pg() calls signal(SIGINT,task) 来中断每个具有group number 为 tty->pgrp的task.值得一提的是，只要process具有相同的group id，不管是backgroud还是foreground，都会被kill掉

从上面的流程我们可以看到，ctrl+C是传送到/dev/ttyS0中的驱动中的。在我原来的文件系统中，建立了节点console作为系统控制台。但是没有ttyS0节点。这样系统运行起来后，shell的交互是通过console这个控制台的。但是在busybox的手册中有这样的一段话：

Why do I keep getting "sh: can't access tty; job control turned off" errors? Why doesn't Control-C work within my shell?

This isn't really a uClibc question, but I'll answer it here anyways. Job control will be turned off since your shell can not obtain a controlling terminal. This typically happens when you run your shell on /dev/console. The kernel will not provide a controlling terminal on the /dev/console device. Your should run your shell on a normal tty such as tty1 or ttyS0 and everything will work perfectly. If you REALLY want your shell to run on /dev/console, then you can hack your kernel (if you are into that sortof thing) by changing drivers/char/tty_io.c to change the lines where it sets "noctty = 1;" to instead set it to "0". I recommend you instead run your shell on a real console...

显然，busybox建议我们shell最好运行在实际的控制台上，例如tty或是ttyS0中。