golang 基于信号实现抢占式调度基本原理

[hustxiaoc]

#define _GNU_SOURCE 1
#include<iostream>
#include<iomanip>
#include<signal.h>
#include <ucontext.h>
#include <unistd.h>

using std::cout;


static void test() {
    cout << "call test function" << std::endl;
}

static volatile int runing = 1;

static void handler(int, siginfo_t *si, void *ptr) {
    ucontext_t *uc = (ucontext_t *)ptr;
    cout << "ip: 0x" << std::hex << uc->uc_mcontext.gregs[REG_RIP] << '\n';
    greg_t sp = uc->uc_mcontext.gregs[REG_RSP];
    sp = sp - 8;
    *((greg_t*)sp) = uc->uc_mcontext.gregs[REG_RIP];
    uc->uc_mcontext.gregs[REG_RIP] = (greg_t)&test;
    uc->uc_mcontext.gregs[REG_RSP] = sp;
    runing = 0;
}

int main()
{
begin:
    cout.setf(std::ios::unitbuf);
    cout << getpid() <<  " ," <<  &&begin << " ~ " << &&before << " ~ " << &&after << '\n';

    struct sigaction s;
    s.sa_flags = SA_SIGINFO|SA_RESETHAND;
    s.sa_sigaction = handler;
    sigemptyset(&s.sa_mask);
    sigaction(SIGUSR1, &s, 0);

    int i = 0;
before:
    do
    {
        i++;
    } while (runing);
    
    cout << "after loop" << std::endl;
after:
    cout << "End.\n";
}

[hustxiaoc]

output

21031 ,0x564298dcc40b ~ 0x564298dcc4e1 ~ 0x564298dcc521
si:0x3e800004e9a
ip: 0x564298dcc4e8
call test function
after loop
End.

使用 kill -USR1 21031 发送信号