使用performSelectorInBackground时，应用程序挂起（__Semwait_signal）

Question

我正在尝试从pushIncompleteDataToServer拨打performSelectorInBackground。它挂起了应用程序。看起来有些死锁问题。我不知道如何解决，因为它是第一次在ios上使用Threads。它挂在__Semwait_signal系统文件中。

如何解决这个问题。 的的Class1

MatchDayDataController *sharedDataController = [MatchDayDataController sharedDataController];
[sharedDataController performSelectorInBackground:@selector( pushIncompleteDataToServer) withObject:nil];

MatchDayDataController类

-(void) pushIncompleteDataToServer
{
    NSManagedObjectContext *context = [self managedObjectContext];
    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
    NSError *error;
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"MatchDayChecklist" inManagedObjectContext:context];
    NSPredicate *predicate = [NSPredicate predicateWithFormat: @"submited == %@" , @2];
    [fetchRequest setEntity:entity];
    [fetchRequest setPredicate:predicate];
    NSArray *record = [context executeFetchRequest:fetchRequest error:&error];
    if (record.count>0)
    {
        for (int i =0; i<record.count; i++)
        {

        NSDictionary *afl =  [self getFormatedDictionary:[record objectAtIndex:i]];

        NSData *jsonData = [NSJSONSerialization dataWithJSONObject:afl options:0 error:&error]; // Use options:NSJSONWritingPrettyPrinted to help with debugging JSON string
        if (!jsonData)
        {
            NSLog(@"Error with JSON data creation: %@", error);
            return;
        }
        // put it the fetched record in matchdaychecklist instacnce so to update submit =2 to 1 when submission is sucessful.
        MatchDayChecklist *matchdata = [record objectAtIndex:i];

        NSString *jsonString = [[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding];
        NSLog(@"Created JSON string: %@", jsonString);
        NSString* jsonDataLength = [NSString stringWithFormat:@"%d", [jsonString length]];

        NSURL* url = [NSURL URLWithString:@"ome urls"];
        NSMutableURLRequest* request = [[NSMutableURLRequest alloc] initWithURL:url];
        [request setHTTPMethod:@"POST"];
        [request setValue:@"application/json; charset=utf-8" forHTTPHeaderField:@"Content-type"];
        [request setValue:jsonDataLength forHTTPHeaderField:@"Content-length"];
        [request setHTTPBody:[jsonString dataUsingEncoding:NSUTF8StringEncoding]];

        [NSURLConnection sendAsynchronousRequest:request
                                           queue:[NSOperationQueue mainQueue]
                               completionHandler:^(NSURLResponse* response, NSData* data, NSError* error)
         {
             if (error != nil)
             {
                 NSLog(@"Submit failed due to: %@", error.localizedDescription);
                 matchdata.submited = @1;
                 NSLog(@"update for : %@" ,matchdata);
                 if (![context save:&error])
                 {
                     NSLog(@"Error saving data.");
                 }
                 return ;
             }

             NSDictionary *dic = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingMutableContainers error:&error];

             //data returned not in the format expected - failure
             if (dic == nil) {
                 NSString *str = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
                 //failure();

                 NSLog(@"Authentication service returned unexpected data: %@", str);

                 return;
             }

             //check if an error has been returned
             NSString *err = [dic objectForKey:@"message"]; //dic[@"error"]
             if (err != nil) {
                // failure();
                 NSLog(@"Submit failed due to: %@", dic[@"error"]);
                 matchdata.submited = @1;
                 NSLog(@"update for : %@" ,matchdata);
                 if (![context save:&error])
                 {
                     NSLog(@"Error saving data.");
                 }
                 return;
             }

             NSLog(@"Submit Successful");

             // Submit is success. so turn submit =2 =>submit =1 and save the context.
//             matchdata.submited = @1;
//             NSLog(@"update for : %@" ,matchdata);
//             if (![context save:&error])
//             {
//                 NSLog(@"Error saving data.");
//             }

         }];
        }

    }

}