Stucking tableview when data come from server

dispatch_async(dispatch_get_global_queue(0,0), ^{
       NSData * imageData = [[NSData alloc] initWithContentsOfURL: [NSURL URLWithString:imageString]];
        NSData * imageData1 = [[NSData alloc] initWithContentsOfURL: [NSURL URLWithString:[NSString stringWithFormat:@"%@%@",IMAGEFETCH,[[storeArray objectAtIndex:indexPath.row] objectAtIndex:10]]]];
        if ( imageData == nil )
            return;
        dispatch_async(dispatch_get_main_queue(), ^{
            // WARNING: is the cell still using the same data by this point??
            cell.img_productImage.image = [UIImage imageWithData: imageData];
            cell.img_logoImage.image = [UIImage imageWithData: imageData1];
        });

    });