进程退出时收到通知

Question

我开发了一个 OSX 守护程序应用程序，用 Qt (C++) 和 Objective-C 编写。我使用内核扩展监控其他应用程序和进程何时启动，但需要知道它们何时终止。

有没有什么方法可以接收到其他进程终止的通知，而不必不断轮询目标进程的pid或mach任务？

Answer 1

你可以用 kqueue/kevent 做到这一点。我破解了一个控制台应用程序，然后对其进行了一些重构，因此发生的事情有些明显，并添加了一个辅助函数以更轻松地调用它。只是几乎没有经过测试，但希望它能给你一个前进的道路......

哦，是的，请注意，此代码假定主运行循环正在应用程序中运行...并且它将从该运行循环中调用该块...简单到可以将其替换为另一个运行循环...或者，如果您没有使用任何 CF 运行循环，则必须将 kq 文件描述符添加到您正在使用的任何通知机制中。

编辑

修复了重新启用回调的错误，因为文件描述符回调必须在每次触发后重新启用。另外，让 args 采用多个 PID 来演示监控多个 PID。

当然，您可以轻松地使用调用委托方法而不是使用块，但这并不是重点...

啊……修复资源泄漏……我可能不会修复更多……因为这是一个被黑的例子，但是每次我回去阅读它时，我都会发现一些错误……也许我会只是停止阅读它:-)

//  main.c

#include <CoreFoundation/CoreFoundation.h>
#include <sys/types.h>
#include <sys/event.h>
#include <sys/time.h>

static void
kqueueCallbackOnExit(CFFileDescriptorRef fileDescriptor,
                     CFOptionFlags flags,
                     void *info)
{
  int fd = CFFileDescriptorGetNativeDescriptor(fileDescriptor);
  struct kevent event;
  if (kevent(fd, NULL, 0, &event, 1, NULL) == 1 && event.udata) {
    void (^cb)(pid_t) = event.udata;
    cb((pid_t)event.ident);
    Block_release(cb);
  }
  CFFileDescriptorEnableCallBacks(
      fileDescriptor, kCFFileDescriptorReadCallBack);
}

static int
createOnProcessExitQueue()
{
  int kq = kqueue();
  if (kq < 0) return -1;

  CFFileDescriptorContext context = {
    .version = 0,
    .info = NULL,
    .retain = NULL,
    .release = NULL,
    .copyDescription = NULL
  };
  CFFileDescriptorRef kqFileDescriptor = CFFileDescriptorCreate(
      NULL, kq, true, kqueueCallbackOnExit, &context);
  if (kqFileDescriptor == NULL) {
    close(kq);
    kq = -1;
    return -1;
  }

  CFRunLoopSourceRef runLoopSource = CFFileDescriptorCreateRunLoopSource(
      NULL, kqFileDescriptor, 0);
  CFRunLoopAddSource(CFRunLoopGetMain(),
      runLoopSource, kCFRunLoopDefaultMode);
  CFRelease(runLoopSource);

  CFFileDescriptorEnableCallBacks(
      kqFileDescriptor, kCFFileDescriptorReadCallBack);
  CFRelease(kqFileDescriptor);

  return kq;
}

static int
onProcessExit(pid_t pid, void (^callback)(pid_t pid))
{
  static int kq;
  static dispatch_once_t onceToken;
  dispatch_once(&onceToken, ^{
    kq = createOnProcessExitQueue();
  });

  void (^cb)(pid_t) = Block_copy(callback);
  struct kevent event = {
    .ident = pid,
    .filter = EVFILT_PROC,
    .flags = EV_ADD | EV_ONESHOT,
    .fflags = NOTE_EXIT,
    .data = 0,
    .udata = (void*)cb
  };

  if (kevent(kq, &event, 1, NULL, 0, NULL) != 1) {
    Block_release(cb);
    return -1;
  }
  return 0;
}

int main(int argc, const char * argv[])
{
  for (int i = 0; i < argc; ++i) {
    pid_t pid = atoi(argv[i]);
    printf("watching pid: %d\n", pid);
    fflush(stdout);
    onProcessExit(pid, ^(pid_t pid) {
      printf("process %d just died\n", (int)pid);
      fflush(stdout);
    });
  }

  CFRunLoopRun();
  return 0;
}

Answer 2

感谢@JodyHagins，我对 kqueue 和 kevent 所做的研究使我找到了this blog，它展示了如何使用 GCD 来监视文件和an example by Apple here。以此为模板，我想出了这个：-

struct ProcessInfo
{
    int pid;
    dispatch_source_t source;
};

// function called back on event
void pid_event(struct ProcessInfo* procinfo)
{
    printf("****** Application exited: %d ******\n", procinfo->pid);
    dispatch_source_cancel(procinfo->source);
}

// function called back when the dispatch source is cancelled
void pid_finalize(struct ProcessInfo* procinfo)
{
    dispatch_release(procinfo->source);
    printf(">>>> Finished with %d <<<<\n", procinfo->pid);
    delete procinfo;
}

// Monitor a process by pid, for termination
void DispatchMonitorProcess(int pid, ProcessInfo* procinfo)
{
    procinfo->pid = pid;

    dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
    dispatch_source_t dsp = dispatch_source_create(DISPATCH_SOURCE_TYPE_PROC, pid, DISPATCH_PROC_EXIT, queue);

    dispatch_source_set_event_handler_f(dsp, (dispatch_function_t)pid_event);
    dispatch_source_set_cancel_handler_f(dsp,  (dispatch_function_t)pid_finalize);

    procinfo->source = dsp;
    dispatch_set_context(dsp, procinfo);

    dispatch_resume(dsp);
}

// Monitors the termination of a process with the given pid
void MonitorTermination(int pid)
{           
   DispatchMonitorProcess(pid, new ProcessInfo);
}

Answer 3

The following example takes a UNIX process ID as argument, and watches up to 20 seconds, and reports if the process terminates in that time

// cc test.c -framework CoreFoundation -O
#include <CoreFoundation/CoreFoundation.h>
#include <unistd.h>
#include <sys/event.h>
static void noteProcDeath(CFFileDescriptorRef fdref, CFOptionFlags callBackTypes, void *info) {
    struct kevent kev;
    int fd = CFFileDescriptorGetNativeDescriptor(fdref);
    kevent(fd, NULL, 0, &kev, 1, NULL);
    // take action on death of process here
    printf("process with pid '%u' died\n", (unsigned int)kev.ident);
    CFFileDescriptorInvalidate(fdref);
    CFRelease(fdref); // the CFFileDescriptorRef is no longer of any use in this example
}
// one argument, an integer pid to watch, required
int main(int argc, char *argv[]) {
    if (argc < 2) exit(1);
    int fd = kqueue();
    struct kevent kev;
    EV_SET(&kev, atoi(argv[1]), EVFILT_PROC, EV_ADD|EV_ENABLE, NOTE_EXIT, 0, NULL);
    kevent(fd, &kev, 1, NULL, 0, NULL);
    CFFileDescriptorRef fdref = CFFileDescriptorCreate(kCFAllocatorDefault, fd, true, noteProcDeath, NULL);
    CFFileDescriptorEnableCallBacks(fdref, kCFFileDescriptorReadCallBack);
    CFRunLoopSourceRef source = CFFileDescriptorCreateRunLoopSource(kCFAllocatorDefault, fdref, 0);
    CFRunLoopAddSource(CFRunLoopGetMain(), source, kCFRunLoopDefaultMode);
    CFRelease(source);
    // run the run loop for 20 seconds
    CFRunLoopRunInMode(kCFRunLoopDefaultMode, 20.0, false);
    return 0;
}

对于那些几乎不知道 C 的人：
构建：cc test.c -framework CoreFoundation -O
运行：./a.out 57168
57168 是被监控进程的pid。杀死它来测试！

当然，你可以延长 20 秒，让它持续多久。