sigwait在Linux（Fedora 13）vs OS X [英] sigwait in Linux (Fedora 13) vs OS X

问题描述

所以我试图创建一个信号处理程序使用pthreads在OS X和Linux上工作。下面的代码适用于OS X，但不适用于Fedora 13。

So I'm trying to create a signal handler using pthreads which works on both OS X and Linux. The code below works on OS X but doesn't work on Fedora 13.

应用程序相当简单。它产生一个pthread，寄存器SIGHUP并等待一个信号。在生成信号处理程序后，我在主线程中阻塞SIGHUP，因此信号应该只发送到signal_handler线程。

The application is fairly simple. It spawns a pthread, registers SIGHUP and waits for a signal. After spawning the signal handler I block SIGHUP in the main thread so the signal should only be sent to the signal_handler thread.

在OS X上这很好，运行并发送SIGHUP到它打印的进程Got SIGHUP。在Linux上，它只会杀死进程（并打印Hangup）。如果我注释掉signal_handler pthread_create的应用程序不会死。

On OS X this works fine, if I compile, run and send SIGHUP to the process it prints "Got SIGHUP". On Linux it just kills the process (and prints Hangup). If I comment out the signal_handler pthread_create the application doesn't die.

我知道应用程序得到sigwait和块，而不是返回信号代码，它只是杀死应用程序。

I know the application gets to the sigwait and blocks but instead of return the signal code it just kills the application.

我使用以下命令运行测试：

I ran the test using the following commands:

g++ test.cc -lpthread -o test
./test &
PID="$!"
sleep 1
kill -1 "$PID"

test.cc

#include <pthread.h>
#include <signal.h>
#include <iostream>

using namespace std;

void *signal_handler(void *arg) {
  int sig;
  sigset_t set;

  sigemptyset(&set);
  sigaddset(&set, SIGHUP);

  while (true) {
    cout << "Wait for signal" << endl;
    sigwait(&set, &sig);
    if (sig == SIGHUP) {
      cout << "Got SIGHUP" << endl;
    }
  }
}

int main() {
  pthread_t handler;
  sigset_t set;

  // Create signal handler
  pthread_create(&handler, NULL, signal_handler, NULL);

  // Ignore SIGHUP in main thread
  sigfillset(&set);
  sigaddset(&set, SIGHUP);
  pthread_sigmask(SIG_BLOCK, &set, NULL);

  for (int i = 1; i < 5; i++) {
    cout << "Sleeping..." << endl;
    sleep(1);
  }

  pthread_join(handler, NULL);
  return 0;
}

推荐答案

sigwait（） 的POSIX规范：

The POSIX spec for sigwait() says:

集合定义的信号在调用
到<$ c时必须有
$ c> sigwait（）;否则，行为
未定义。

The signals defined by set shall have been blocked at the time of the call to sigwait(); otherwise, the behavior is undefined.

你不这样做。如果您添加：

You're not doing this. If you add:

pthread_sigmask(SIG_BLOCK, &set, NULL);

$ b $ p < sigaddset（），那么它可以正常工作。

to your signal_handler() function immediately after the sigaddset(), then it works correctly.

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