`deleteMessages` holds a write transaction for 39 s, blocking the controller queue and all DB readers

Checklist

• I have used the search function to see if someone else has already submitted the same bug report.
• I will describe the problem with as much detail as possible.

App

Thunderbird for Android

App version

22.0

Where did you get the app from?

F-Droid

Android version

12

Device model

OnePlus 13

Steps to reproduce

Delete a message from the inbox over IMAP (Cyrus IMAP < 3.0 with no MOVE extension).

Expected behavior

This should work flawlessly.

Actual behavior

The app either hangs or is sluggish.

claude-opus-5 analysis:

Deleting one INBOX message (account with no trash folder) stalled MessagingController's single command thread:

08:44:04.736 Running command 'deleteMessages', seq = 27 (background priority)
08:44:04.737 Not moving deleted messages to local Trash folder. Removing local copies.
   (tid 26870 silent until the log ends at 08:44:43.416)

runInBackground() logs completion or error unconditionally, so the thread never returned.
LockableDatabase's Transaction ended line never appeared (debug logging was on), nor did
Log.d("Delete policy for account …") at MessagingController.java:2147 — so it is stuck inside
localFolder.setFlags(…, DELETED, …), line 2105.

The pool holds one connection, so every other reader starved:

08:44:34.746 W SQLiteConnectionPool: … unable to grant a connection to thread 121108
  (ForkJoinPool.commonPool-worker-3) with flags 0x1 for 30.000002 seconds.
  Connections: 0 active, 1 idle, 0 available.
  … MessageListRemoteViewFactory.onDataSetChanged → MessageListLoader.getMessageListInfo
  → DefaultMessageListRepository.getThreadedMessages → LockableDatabase.execute

Suspected cause: LocalMessage.setFlag()/delete() call localStore.notifyChange()
(LocalMessage.java:291, 334) inside the transaction opened by LocalFolder.setFlags
(LocalFolder.java:853). DefaultMessageListRepository notifies listeners synchronously, so
MessageListWidgetManager reloads the widget, which queries the locked database — a lock-order
inversion.

Knock-on: a checkMail wake lock was taken at 08:44:06.502 for a command that never ran;
queueDelete/processPendingCommands (lines 2168/2176) were never reached, so no
UID STORE \Deleted was sent. The message vanished server-side only after an app restart.

Logs

k9mail-logs_4.redacted.txt

Reproduce deletion over IMAP with Cyrus IMAP lacking MOVE, then inspect LocalFolder.java:853 and LocalMessage.java:291,334 around transaction and notification handling. Trace the synchronous reload through DefaultMessageListRepository and MessageListWidgetManager, and verify that deletion completes, UID STORE is sent, and database readers are not blocked.