Fix database deadlock in contacts manager.

// FREEBIE

Signal/src/contact/OWSContactsManager.m

@@ -207,11 +207,21 @@ void onAddressBookChanged(ABAddressBookRef notifyAddressBook, CFDictionaryRef in
         NSMutableDictionary<NSString *, SignalAccount *> *signalAccountMap = [NSMutableDictionary new];
         NSMutableArray<SignalAccount *> *signalAccounts = [NSMutableArray new];
         NSArray<Contact *> *contacts = self.allContacts;
+
+        // We use a transaction only to load the SignalRecipients for each contact,
+        // in order to avoid database deadlock.
+        NSMutableDictionary<NSString *, NSArray<SignalRecipient *> *> *contactIdToSignalRecipientsMap =
+            [NSMutableDictionary new];
         [[TSStorageManager sharedManager].dbConnection readWithBlock:^(YapDatabaseReadTransaction *transaction) {
             for (Contact *contact in contacts) {
                 NSArray<SignalRecipient *> *signalRecipients = [contact signalRecipientsWithTransaction:transaction];
-                for (SignalRecipient *signalRecipient in
-                    [signalRecipients sortedArrayUsingSelector:@selector(compare:)]) {
+                contactIdToSignalRecipientsMap[contact.uniqueId] = signalRecipients;
+            }
+        }];
+
+        for (Contact *contact in contacts) {
+            NSArray<SignalRecipient *> *signalRecipients = contactIdToSignalRecipientsMap[contact.uniqueId];
+            for (SignalRecipient *signalRecipient in [signalRecipients sortedArrayUsingSelector:@selector(compare:)]) {
                 SignalAccount *signalAccount = [[SignalAccount alloc] initWithSignalRecipient:signalRecipient];
                 signalAccount.contact = contact;
                 if (signalRecipients.count > 1) {
@@ -227,7 +237,6 @@ void onAddressBookChanged(ABAddressBookRef notifyAddressBook, CFDictionaryRef in
                 [signalAccounts addObject:signalAccount];
             }
         }
-        }];
 
         dispatch_async(dispatch_get_main_queue(), ^{
             self.signalAccountMap = [signalAccountMap copy];