Question

我编写了一个Qt5 / C ++程序，该程序在后台运行并运行，并在响应信号时停止并正常关闭。一切听起来都不错，但是当我“ps ax | grep myprog”时，我看到一堆程序仍在运行;例如：

29244 ?        Ss   149:47 /usr/local/myprog/myprog -q
30913 ?        Ss     8:37 /usr/local/myprog/myprog -q
32484 ?        Ss     0:11 /usr/local/myprog/myprog -q

如果我在前台运行该程序，那么该进程不会在进程列表中停留 - 它会按预期消失。这只发生在后台。为什么呢？

更新：我发现我的程序处于futex_wait_queue_me状态（queue_me并等待唤醒，超时或信号）。我确实有3个单独的线程 - 这可能是相关的。所以我将一个调试器连接到其中一个等待进程，发现了这个：

(gdb) bt
#0  0x000000372460b575 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib64/libpthread.so.0
#1  0x00007f8990fb454b in QWaitCondition::wait(QMutex*, unsigned long) ()
   from /opt/Qt/5.1.1/gcc_64/lib/libQt5Core.so.5
#2  0x00007f8990fb3b3e in QThread::wait(unsigned long) () from /opt/Qt/5.1.1/gcc_64/lib/libQt5Core.so.5
#3  0x00007f8990fb0402 in QThreadPoolPrivate::reset() () from /opt/Qt/5.1.1/gcc_64/lib/libQt5Core.so.5
#4  0x00007f8990fb0561 in QThreadPool::waitForDone(int) () from /opt/Qt/5.1.1/gcc_64/lib/libQt5Core.so.5
#5  0x00007f89911a4261 in QMetaObject::activate(QObject*, int, int, void**) ()
   from /opt/Qt/5.1.1/gcc_64/lib/libQt5Core.so.5
#6  0x00007f89911a4d5f in QObject::destroyed(QObject*) () from /opt/Qt/5.1.1/gcc_64/lib/libQt5Core.so.5
#7  0x00007f89911aa3ee in QObject::~QObject() () from /opt/Qt/5.1.1/gcc_64/lib/libQt5Core.so.5
#8  0x0000000000409d8b in main (argc=1, argv=0x7fffba44c8f8) at ../../src/main.cpp:27
(gdb)

更新：

我注释掉了我的2个线程，所以现在只运行主线程，问题是一样的。

是否有一种特殊方法可以导致后台进程退出？为什么主线程不会关闭？

更新：解决了 - Qt不喜欢福克。（参见另一个StackExchane questoin）。我不得不把我的叉子移到最高级别（在Qt做任何事情之前），然后Qt不会在退出时挂起。

Answer 1

http://man7.org/linux/man-pages/man1/ps.1.html#PROCESS_STATE%20CODES

处理状态代码

以下是 s ， stat 和状态输出说明符（标题“STAT”或“S”）将显示的不同值描述一个过程的状态：

  D    uninterruptible sleep (usually IO)
  R    running or runnable (on run queue)
  S    interruptible sleep (waiting for an event to complete)
  T    stopped, either by a job control signal or because it is being traced.
  W    paging (not valid since the 2.6.xx kernel)
  X    dead (should never be seen)
  Z    defunct ("zombie") process, terminated but not reaped by its parent.

对于BSD格式，当使用stat关键字时，可能会显示其他字符：

  <    high-priority (not nice to other users)
  N    low-priority (nice to other users)
  L    has pages locked into memory (for real-time and custom IO)
  s    is a session leader
  l    is multi-threaded (using CLONE_THREAD, like NPTL pthreads do)
  +    is in the foreground process group.

所以你的过程都处于“S：可中断睡眠”。也就是说，他们都在等待阻止系统调用。

您可能有更好的提示，说明您的程序正在等待此命令：

$ ps -o pid,stat,wchan `pidof zsh`
  PID STAT WCHAN
 4490 Ss   rt_sigsuspend
 4814 Ss   rt_sigsuspend
 4861 Ss   rt_sigsuspend
 4894 Ss+  n_tty_read
 5744 Ss+  n_tty_read
...

“wchan（等待通道）”显示阻塞的内核函数（= ~syscall）。

另见

https://askubuntu.com/questions/19442/what-is-the-waiting-channel-of-a-process

QThreaded C ++守护程序未正常关闭

1 个答案: