ios - CFRunLoopWakeUp 不起作用？

Question

在我的案例中，CFRunLoopWakeUp 似乎无法正常工作。这是设置:

我在等待某些工作完成的主线程上有一个“典型的”while 循环not:

- (void)someFunc
{
    self.runLoop = CFRunLoopGetCurrent();
    NSLog(@"Pre loop.");
    while (!self.completed)
    {
        NSLog(@"In loop.");
        NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
        [[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDate distantFuture]];
        [pool release];
    }
    NSLog(@"Post loop.");
}

我有一个回调函数，等待某些工作完成。这也不从主线程调用:

- (void)callback
{
    NSLog(@"Work completed.");
    self.completed = YES;

    // I've checked that CFRunLoopIsWaiting(self.runLoop) here returns true
    CFRunLoopWakeUp(self.runLoop); // Should wake up the waiting run loop, but doesn't!
}

调用了回调，但由于某些原因，CFRunLoopWakeUp 似乎没有做任何事情。我错过了一些明显的东西吗？这里是否存在一些深度线程问题？谢谢!

Answer 1

首先，我无法重现您的问题。我像这样在 GCD 中构建它:

int main (int argc, const char *argv[])
{
  @autoreleasepool {
    __block BOOL completed = NO;
    __block CFRunLoopRef runLoop;

    dispatch_queue_t queue1 = dispatch_queue_create("first", 0);
    dispatch_queue_t queue2 = dispatch_queue_create("second", 0);

    dispatch_async(queue1, ^{
      runLoop = CFRunLoopGetCurrent();
      NSLog(@"Pre loop.");
      while (!completed)
      {
        NSLog(@"In loop.");
        @autoreleasepool {
          [[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDate distantFuture]];
        }
      }
      NSLog(@"Post loop.");
    });

    double delayInSeconds = 2.0;
    dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, (unsigned)(delayInSeconds * NSEC_PER_SEC));
    dispatch_after(popTime, queue2, ^(void) {
      NSLog(@"Work completed.");
      completed = YES;

      // I've checked that CFRunLoopIsWaiting(self.runLoop) here returns true
      CFRunLoopWakeUp(runLoop); // Should wake up the waiting run loop, but doesn't!

    });

    dispatch_sync(queue1, ^{});
    dispatch_sync(queue2, ^{});
    dispatch_release(queue1);
    dispatch_release(queue2);
  }
  return 0;
}

你能构建一个更简单的程序来演示问题吗？

我会尝试的其他事情，主要是为了调试以缩小问题范围:

• 切换到 CFRunLoopRunInMode() 而不是 runinMode:beforeDate:。它们略有不同。
• 切换到 CFRunLoopStop() 而不是 CFRunLoopWakeUp()。

当然，请确保 self.runLoop 实际上指向您认为它指向的运行循环!