在多线程进程中处理信号的示例

Question

任何人都可以给我以下情况的步骤甚至代码:

包含多个线程的进程以及这些线程负责捕获用户定义的信号SIGUSR1.只有这个线程应该能够接收到这个信号,并且在接收到这个信号后我会做一些事情.

在我的情况下,内核模块将信号发送到我的进程ID.然后我的过程负责将它传递给正确的监听线程,该线程还建立了信号处理程序,即信号处理程序不在主线程中.

我已经为一个单线程进程运行了一些代码,但是在多线程环境中运行它时遇到了问题.

我在Linux Ubuntu 12.04.3上使用内核版本3.8.0-29运行我的代码.为了创建流程,我将在Boost Threads和POSIX threads API之间进行混合.

#include <unistd.h>
#include <signal.h>
#include <stdio.h>
#include <malloc.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/mman.h>
#include <string.h>

/* Value of the last signal caught */
volatile sig_atomic_t sig_value;

static void sig_handler(const int sig_number, siginfo_t *sig_info, void *context)
{
if (sig_number == SIGSEGV)
{
    error_sys("Error at address 0x%lx", (long)sig_info->si_addr);
    exit(-1);
}
sig_value = sig_number;
}


int init_signal_catcher()
{
struct sigaction sig_action; /* Structure describing the action to be taken when asignal arrives.  */

sigset_t oldmask;  /* Signal mask before signal disposition change.      */
sigset_t newmask;  /* Signal mask after signal disposition change.       */
sigset_t zeromask; /* Signal mask to unblock all signal while suspended. */

/* Define signal mask and install signal handlers */
memset(&sig_action, 0, sizeof(struct sigaction));

sig_action.sa_flags = SA_SIGINFO;
sig_action.sa_sigaction = sig_handler;

/* Examine and change a signal action. */
sigaction(SIGHUP, &sig_action, NULL);
sigaction(SIGINT, &sig_action, NULL);
sigaction(SIGTERM, &sig_action, NULL);
sigaction(SIGSEGV, &sig_action, NULL);
sigaction(SIGUSR1, &sig_action, NULL);

    /* Block SIGHUP, SIGINT, SIGTERM, SIGSEGV and SIGUSR1 signals. */
sigemptyset(&newmask);
sigaddset(&newmask, SIGHUP);
sigaddset(&newmask, SIGINT);
sigaddset(&newmask, SIGTERM);
sigaddset(&newmask, SIGSEGV);
sigaddset(&newmask, SIGUSR1);

/* Examine and change blocked signals. */
pthread_sigmask(SIG_BLOCK, &newmask, &oldmask);

/* Initialize the empty signal set. */
sigemptyset(&zeromask);
sig_value = 0;

while ((sig_value != SIGINT) && (sig_value != SIGTERM))
{
    sig_value = 0;

    /*
     * Go to sleep (unblocking all signals) until a signal is catched.
     * On return from sleep, the signals SIGHUP, SIGINT, SIGTERM and
         * SIGUSR1 are again blocked.
     */
        printf("Suspending on %lu mask.", zeromask);

        // Wait for a signal.
    sigsuspend(&zeromask);

    switch(sig_value)
    {
                printf("Caught Signal %d", sig_value);
        case SIGUSR1:
                    printf("Caught SIGUSR1");
                    break;
    }
}

return 0;
}

Answer 1

需要在每个线程中阻止信号。最安全的方法是在创建任何其他线程之前在第一个线程中阻止它们。然后一个专门选择的线程可以调用sigsuspend()，并且只有该线程将执行信号处理程序。

\n\n

void *signal_handling_thread(void *whatever) {\n  sig_value := 0\n  while (sig_value not in (SIGTERM, SIGINT)) {\n    sigsuspend(empty_mask)\n    ...\n  }\n  ...\n}\n\nint main(int argc, char **argv) {\n  block_relevant_signals();               // SIG_BLOCK HUP, TERM, USR1, etc.\n  catch_relevant_signals();               // SA_SIGINFO ...\n\n  spawn_signal_handling_thread();         // spawned with relevant signals blocked\n\n  for (int i = 0; i < NUM_WORKERS; i++) {\n    spawn_worker_thread();                // spawned with relevant signals blocked\n  }\n  ...\n}\n

\n\n

是时候重构您的代码来分解关注点 \xe2\x80\x94 在一个地方进行全局进程属性操作，在另一个地方进行特定于信号的反应，等等。

\n