diff options
Diffstat (limited to 'src/mongo/db/s/transaction_coordinator_util.cpp')
| -rw-r--r-- | src/mongo/db/s/transaction_coordinator_util.cpp | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/src/mongo/db/s/transaction_coordinator_util.cpp b/src/mongo/db/s/transaction_coordinator_util.cpp index 6c71a3071cb..776ead96215 100644 --- a/src/mongo/db/s/transaction_coordinator_util.cpp +++ b/src/mongo/db/s/transaction_coordinator_util.cpp @@ -351,6 +351,15 @@ repl::OpTime persistDecisionBlocking(OperationContext* opCtx, sessionInfo.setTxnRetryCounter(*txnNumberAndRetryCounter.getTxnRetryCounter()); } + // The transaction participant is already holding a global IX lock (and therefore an FCV IX + // lock) when we get to this point. Since the setFCV command takes an FCV S lock, we can hit a + // deadlock if the setFCV enqueues its lock after the transaction participant has already + // acquired its lock, but before we (the transaction coordinator) acquire ours. To remedy this, + // we choose to bypass this barrier that setFCV creates. This is safe because the setFCV command + // drains any outstanding cross-shard transactions before completing an FCV upgrade/downgrade. + // It does so by waiting for the participant portion of the cross-shard transaction to have + // released its FCV IX lock. + ShouldNotConflictWithSetFeatureCompatibilityVersionBlock noFCVLock{opCtx->lockState()}; DBDirectClient client(opCtx); // Throws if serializing the request or deserializing the response fails. |