读书笔记：第5章 Posix消息队列 (10)
《UNIX网络编程：卷2》P81-P84：图5-17、5-18
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该程序先调用fork，子进程阻塞三种实时信号，父进程随后发送9个信号（三种实时信号每种3个），子进程接着解阻塞信号，我们于是看到每种信号各有多少个递交以及它们的先后递交顺序。
/*
* test1.c
* 图5-17 演示实时信号的简单测试程序
*/
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <signal.h>
#include <string.h>
#include <errno.h>
typedef void sigfunc_rt(int, siginfo_t *, void *);
sigfunc_rt *signal_rt(int signo, sigfunc_rt *func, sigset_t *mask);
static void sig_rt(int signo, siginfo_t *info, void *context);
int main(int argc, char *argv[])
{
int i, j;
pid_t pid;
sigset_t newset;
union sigval val;
// 输出最小和最大实时信号值
printf("SIGRTMIN = %d, SIGRTMAX = %d\n", SIGRTMIN, SIGRTMAX);
// 派生一个子进程
if ((pid = fork()) < 0) {
fprintf(stderr, "fock error %s\n", strerror(errno));
exit(1);
} else if (pid == 0) {
// 子进程
sigemptyset(&newset); // 初始化信号集
sigaddset(&newset, SIGRTMAX); // 添加三种实时信号
sigaddset(&newset, SIGRTMAX - 1);
sigaddset(&newset, SIGRTMAX - 2);
sigprocmask(SIG_BLOCK, &newset, NULL); // 阻塞这三种实时信号
// 建立三种实时信号的处理程序
signal_rt(SIGRTMAX , sig_rt, &newset);
signal_rt(SIGRTMAX - 1, sig_rt, &newset);
signal_rt(SIGRTMAX - 2, sig_rt, &newset);
sleep(6); // 等待6秒，以允许父进程产生信号
sigprocmask(SIG_UNBLOCK, &newset, NULL); // 为这三种实时信号的解除阻塞
sleep(3); // 等待3秒，以便信号处理程序调用printf函数9次
exit(0);
}
// 父进程
sleep(3); // 等待3秒，以便子进程阻塞所有信号
// 为三种实时信号各产生3个信号
for (i = SIGRTMAX; i >= SIGRTMAX - 2; i--) {
for (j = 0; j <= 2; j++) {
val.sival_int = j; // 同种信号伴随不同整数
sigqueue(pid, i, val); // 向指定进程发送信号，携带不同整数
printf("sent signal %d, val = %d\n", i, j);
}
}
exit(0);
}
static void sig_rt(int signo, siginfo_t *info, void *context)
{
printf("received signal #%d, code = %d, ival = %d\n",
signo, info->si_code, info->si_value.sival_int);
}
/*
* signal_rt.c
* P84 图5-18 提供实时行为的signal_rt函数
*/
sigfunc_rt *signal_rt(int signo, sigfunc_rt *func, sigset_t *mask)
{
struct sigaction act, oact;
act.sa_sigaction = func; // 信号处理程序地址
act.sa_mask = *mask; // 执行信号处理程序时阻塞的信号集
act.sa_flags = SA_SIGINFO; // 实时信号必须指定的标志
if (signo == SIGALRM) {
#ifdef SA_INTERRUPT
act.sa_flags |= SA_INTERRUPT;
#endif
} else {
#ifdef SA_RESTART
act.sa_flags |= SA_RESTART;
#endif
}
// 信号与信号动作关联
if (sigaction(signo, &act, &oact) < 0)
return((sigfunc_rt *)SIG_ERR);
return(oact.sa_sigaction);
}
运行程序：
$ ./test1 SIGRTMIN = 34, SIGRTMAX = 64 sent signal 64, val = 0 sent signal 64, val = 1 sent signal 64, val = 2 sent signal 63, val = 0 sent signal 63, val = 1 sent signal 63, val = 2 sent signal 62, val = 0 sent signal 62, val = 1 sent signal 62, val = 2 $ received signal #62, code = -1, ival = 0 父进程终止，shell提示符输出 received signal #62, code = -1, ival = 1 received signal #62, code = -1, ival = 2 received signal #63, code = -1, ival = 0 received signal #63, code = -1, ival = 1 received signal #63, code = -1, ival = 2 received signal #64, code = -1, ival = 0 received signal #64, code = -1, ival = 1 received signal #64, code = -1, ival = 2
父进程发送的9个信号排队后按我们期待的顺序递交：值最小的信号最先递交。对于一种给定信号，它的三次发送按FIFO顺序递交。