- T1: test calls fsync on mongos
- T1: mongos runs fsync on CSRS primary
- T1: CSRS primary takes global S
- T2: test hook calls replSetStepDown
- T2: replSetStepDown marks CSRS as kReplicaSetNoPrimary
- T2: replSetStepDown waits for global X (blocked by T1 global S)
- T1: CSRS fsync returns to mongos
- T1: mongos tries to resolve hosts from shardIds (appendRawResponses function)
- T1: mongos tries to read config.shards from CSRS primary (stepdown forces shard catalog reload)
- T1: mongos waits for CSRS primary (as replSetStepDown marked CSRS as ReplicaSetNoPrimary)
--- deadlock ---
- T2: replSetStepDown times out on waiting for global X
- T2: replSetStepDown resets CSRS topology (kReplicaSetWithPrimary)
- T1: mongos finds CSRS primary, refreshes, finishes fsync
- T2: replSetStepDown reports LockTimeout to test hook
- T2: test hook fails the test