linux signals 进程信号简介 -凯发k8官方网

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在linux中，signal是一种局限较强的进程间通信方式。

主要有三种类型：

1. 从hardware signal到posix signal

    hardware signal也叫hardware interrupt，cpu中存放着 interrupt vectors 指向 存放在kernel space中的interrupt handling routine。

    例： 键盘输入；segmentation fault -> sigsegv 

2. 直接从kernel生成的posix signal

    例：exit() -> sigchld

3. 从一个进程发起到另一个进程的signal

    例：进程885 执行了 “kill 1234” 代码

posix signal

1. generated from cpu to kernel, or from cpu to processes

    例 1: segmentation fault.
        the signal is labeled sigsegv, which comes from cpu to kernel then to process.
    例 2: floating point exception (e.g., divided by 0).
        the signal is labeled sigfpe, which is coming from cpu to process

2. from kernel to process

    例: child process termination.
        the signal is labeled sigchld, which is coming from the kernel to process

3. generated from one process to another

    例： from terminals: e.g., “ctrl c”, “ctrl z”
            using programs: e.g., “kill”, “top”, etc.
            using the “kill()” system call.

一些典型的signal

asynchronous signal: 异步信号
– the signal received is not generated by the process itself。 so, its arrival time is usually not deterministic
– e.g., external hardware interrupt, another process sends ctrl-c

synchronous signal: 同步信号
– the signal is caused by the process itself, its arrival time is usually deterministic
– e.g., a certain line leads to sigfpe 
– e.g., a certain line accesses a memory region: sigsegv

kill() 方法

用于给特地进程发送posix signal

signal() 方法

更新当前进程的特定signal的处理方法，即signal handler

例：写个无法“ctrl c”中止的小病毒