Iphone 从主线程或web线程以外的线程获取web锁

我正在制作一个需要与服务器（S3）通信的iPhone应用程序。但是，当我执行此代码时：

- (void)submit
{
    dispatch_queue_t Q = dispatch_queue_create("Formula Submit", NULL);
    dispatch_async(Q, ^{
        NSMutableArray *formulas = [[NSArray arrayWithContentsOfURL:[NSURL URLWithString:@"https://urlremoved.com"]] mutableCopy];

        if (!formulas)
        {
            formulas = [[NSMutableArray alloc] init];
        }

       [_data addEntriesFromDictionary:[[NSDictionary alloc] initWithObjectsAndKeys:self.explanationTextView.text, @"explanation", nil]];

        [formulas addObject:_data];

        AmazonS3Client *s3 = [[AmazonS3Client alloc] initWithAccessKey:@"Access Key Removed" withSecretKey:@"Secret Key Removed"];

        S3PutObjectRequest *por = [[S3PutObjectRequest alloc] initWithKey:@"File Name Removed" inBucket:@"Bucket Name Removed"];
        por.contentType = @"application/octet-stream";

        NSData *plistData = [NSPropertyListSerialization dataFromPropertyList:formulas format:NSPropertyListBinaryFormat_v1_0 errorDescription:nil];

        por.data = plistData;
        [s3 putObject:por];
    });

    [self dismissModalViewControllerAnimated:YES];
}

我在控制台中收到以下错误/警告：

void _WebThreadLockFromAnyThread(bool), 0x20150be0: Obtaining the web lock from a thread other than the main thread or the web thread. UIKit should not be called from a secondary thread.

此消息似乎不会以任何方式影响应用程序性能。它成功地上传到S3，没有明显的问题

---

从本质上说，我想知道是否有办法让这个信息消失

访问下面的链接，它会让你知道这里没有UI操作。我认为下面的编码可以完成UI工作[self-dismissModalViewControllerAnimated:YES]；是的，但它不在

dispatch\u async

块的范围内。