MBProgressHUD goes background - facebook

Question

I am doing Facebook integration, first i have to authenticate and then i have to fetch details. During this process i am showing HUD loader. After authentication the Hud fades and not showing clearly.My code follows,please suggest me if i am doing anything wrong.
-(IBAction)btn_FacebookClicked:(id)sender
{
HUD = [[MBProgressHUD alloc] initWithView:self.view];
[self.view addSubview:HUD];
HUD.delegate = self;
HUD.labelText =#"Loading";
HUD.dimBackground=YES;
[HUD show:YES];
[self performSelectorInBackground:#selector(FacebookLogin) withObject:nil];
}
-(void)FacebookLogin
{
if(!accountStore)
accountStore = [[ACAccountStore alloc] init];
ACAccountType *facebookTypeAccount = [accountStore accountTypeWithAccountTypeIdentifier:ACAccountTypeIdentifierFacebook];
[accountStore requestAccessToAccountsWithType:facebookTypeAccount
options:#{ACFacebookAppIdKey: #"**********", ACFacebookPermissionsKey: #[#"email"]}
completion:^(BOOL granted, NSError *error) {
if(granted){
NSArray *accounts = [accountStore accountsWithAccountType:facebookTypeAccount];
facebookAccount = [accounts lastObject];
NSLog(#"Success");
[self userfbDetail];
}else{
// ouch
[HUD hide:YES];
NSLog(#"Fail");
NSLog(#"Error: %#", error);
}
}];
}
}
// Get user facebook details
- (void)userfbDetail{
NSURL *meurl = [NSURL URLWithString:#"https://graph.facebook.com/me"];
SLRequest *merequest = [SLRequest requestForServiceType:SLServiceTypeFacebook
requestMethod:SLRequestMethodGET
URL:meurl
parameters:nil];
merequest.account = facebookAccount;
[merequest performRequestWithHandler:^(NSData *responseData, NSHTTPURLResponse *urlResponse, NSError *error) {
// NSString *meDataString = [[NSString alloc] initWithData:responseData encoding:NSUTF8StringEncoding];
NSMutableArray *arr_facebook=[[NSMutableArray alloc]init];
arr_facebook=[NSJSONSerialization JSONObjectWithData:responseData options:kNilOptions error:&error];
NSString *firstname=[arr_facebook valueForKey:#"name"];
NSString *user=[NSString stringWithFormat:#"Welcome %#",firstname];
ALERT(user);
[HUD hide:YES];
}];
}