SERVER-31431 Ensure that all state transitions in or out of SECONDARY occur with the global X lock held

3 files changed, 28 insertions, 19 deletions

diff --git a/src/mongo/db/repl/bgsync.cpp b/src/mongo/db/repl/bgsync.cpp
index 1ae84415b4a..f2c369ea0bd 100644
--- a/src/mongo/db/repl/bgsync.cpp
+++ b/src/mongo/db/repl/bgsync.cpp
@@ -364,6 +364,10 @@ void BackgroundSync::_produce() {
         // Mark yourself as too stale.
         _tooStale = true;
 
+        // Need to take global X lock to transition out of SECONDARY.
+        auto opCtx = cc().makeOperationContext();
+        Lock::GlobalWrite globalWriteLock(opCtx.get());
+
         error() << "too stale to catch up -- entering maintenance mode";
         log() << "Our newest OpTime : " << lastOpTimeFetched;
         log() << "Earliest OpTime available is " << syncSourceResp.earliestOpTimeSeen;
diff --git a/src/mongo/db/repl/resync.cpp b/src/mongo/db/repl/resync.cpp
index c18c26bfd46..a1e60050652 100644
--- a/src/mongo/db/repl/resync.cpp
+++ b/src/mongo/db/repl/resync.cpp
@@ -90,23 +90,28 @@ public:
                            "Replica sets do not support the resync command"));
             }
 
-            const MemberState memberState = replCoord->getMemberState();
-            if (memberState.startup()) {
-                return appendCommandStatus(
-                    result, Status(ErrorCodes::NotYetInitialized, "no replication yet active"));
-            }
-            if (memberState.primary()) {
-                return appendCommandStatus(
-                    result, Status(ErrorCodes::NotSecondary, "primaries cannot resync"));
-            }
-            auto status = replCoord->setFollowerMode(MemberState::RS_STARTUP2);
-            if (!status.isOK()) {
-                return appendCommandStatus(
-                    result,
-                    Status(status.code(),
-                           str::stream()
-                               << "Failed to transition to STARTUP2 state to perform resync: "
-                               << status.reason()));
+            {
+                // Need global write lock to transition out of SECONDARY
+                Lock::GlobalWrite globalWriteLock(opCtx);
+
+                const MemberState memberState = replCoord->getMemberState();
+                if (memberState.startup()) {
+                    return appendCommandStatus(
+                        result, Status(ErrorCodes::NotYetInitialized, "no replication yet active"));
+                }
+                if (memberState.primary()) {
+                    return appendCommandStatus(
+                        result, Status(ErrorCodes::NotSecondary, "primaries cannot resync"));
+                }
+                auto status = replCoord->setFollowerMode(MemberState::RS_STARTUP2);
+                if (!status.isOK()) {
+                    return appendCommandStatus(
+                        result,
+                        Status(status.code(),
+                               str::stream()
+                                   << "Failed to transition to STARTUP2 state to perform resync: "
+                                   << status.reason()));
+                }
             }
             uassertStatusOKWithLocation(replCoord->resyncData(opCtx, waitForResync), "resync", 0);
             return true;
diff --git a/src/mongo/db/repl/sync_tail.cpp b/src/mongo/db/repl/sync_tail.cpp
index 15e6fabb856..15185abaf73 100644
--- a/src/mongo/db/repl/sync_tail.cpp
+++ b/src/mongo/db/repl/sync_tail.cpp
@@ -691,8 +691,8 @@ void tryToGoLiveAsASecondary(OperationContext* opCtx, ReplicationCoordinator* re
     // This needs to happen after the attempt so readers can be sure we've already tried.
     ON_BLOCK_EXIT([] { attemptsToBecomeSecondary.increment(); });
 
-    // TODO(SERVER-27892): Change to GlobalWrite
-    Lock::GlobalRead readLock(opCtx);
+    // Need global X lock to transition to SECONDARY
+    Lock::GlobalWrite readLock(opCtx);
 
     if (replCoord->getMaintenanceMode()) {
         LOG(1) << "Can't go live (tryToGoLiveAsASecondary) as maintenance mode is active.";