Currently, there is a 3 way deadlock. Assume that we are transitioning from secondary to primary(signalDrainComplete).
- Thread A (Read thread) acquires RSTL lock in IX and blocked by a prepared txn due to prepare conflict.
- Stepup enqueues RSTL lock in X mode. And blocked behind A.
- Prepared txn won’t be able commit until we are able to change our state to primary.
Alternatively, thread A might have got blocked on prepare conflict due to conflicting DB/ collection lock. For eg. dbhash cmd.
EDIT: Blocked due to conflicting mongoDB locks is not possible as secondary prepared txn yield mongoDB locks.