SERVER-52564 Deadlock between step down and MongoDOperationContextSession

(cherry picked from commit 6ee5a25cfc951f6e914dcc9f7d1a63d2e7aeaa67)

3 files changed, 59 insertions, 0 deletions

diff --git a/src/mongo/db/repl/replication_coordinator_impl.cpp b/src/mongo/db/repl/replication_coordinator_impl.cpp
index d375b54f735..16bc218e87e 100644
--- a/src/mongo/db/repl/replication_coordinator_impl.cpp
+++ b/src/mongo/db/repl/replication_coordinator_impl.cpp
@@ -2509,6 +2509,11 @@ void ReplicationCoordinatorImpl::stepDown(OperationContext* opCtx,
     CurOpFailpointHelpers::waitWhileFailPointEnabled(
         &stepdownHangBeforeRSTLEnqueue, opCtx, "stepdownHangBeforeRSTLEnqueue");
 
+    // To prevent a deadlock between session checkout and RSTL lock taking, disallow new sessions
+    // from being checked out. Existing sessions currently checked out will be killed by the
+    // killOpThread.
+    ScopedBlockSessionCheckouts blockSessions(opCtx);
+
     // Using 'force' sets the default for the wait time to zero, which means the stepdown will
     // fail if it does not acquire the lock immediately. In such a scenario, we use the
     // stepDownUntil deadline instead.
diff --git a/src/mongo/db/session_catalog.cpp b/src/mongo/db/session_catalog.cpp
index 55911f5a802..23934323e84 100644
--- a/src/mongo/db/session_catalog.cpp
+++ b/src/mongo/db/session_catalog.cpp
@@ -80,6 +80,10 @@ SessionCatalog::ScopedCheckedOutSession SessionCatalog::_checkOutSession(Operati
     invariant(!opCtx->lockState()->isLocked());
 
     stdx::unique_lock<Latch> ul(_mutex);
+    uassert(ErrorCodes::InterruptedDueToReplStateChange,
+            "a stepdown process started, can't checkout sessions except for killing",
+            _checkoutAllowed);
+
     auto sri = _getOrCreateSessionRuntimeInfo(ul, opCtx, *opCtx->getLogicalSessionId());
 
     // Wait until the session is no longer checked out and until the previously scheduled kill has
@@ -176,6 +180,16 @@ void SessionCatalog::scanSessions(const SessionKiller::Matcher& matcher,
     }
 }
 
+void SessionCatalog::_disallowCheckoutsExceptForKilling() {
+    stdx::unique_lock<Latch> ul(_mutex);
+    _checkoutAllowed = false;
+}
+
+void SessionCatalog::_allowCheckouts() {
+    stdx::lock_guard<Latch> lg(_mutex);
+    _checkoutAllowed = true;
+}
+
 SessionCatalog::KillToken SessionCatalog::killSession(const LogicalSessionId& lsid) {
     stdx::lock_guard<Latch> lg(_mutex);
     auto it = _sessions.find(lsid);
@@ -325,4 +339,12 @@ void OperationContextSession::checkOut(OperationContext* opCtx) {
     checkedOutSession.emplace(std::move(scopedCheckedOutSession));
 }
 
+ScopedBlockSessionCheckouts::ScopedBlockSessionCheckouts(OperationContext* opCtx) : _opCtx(opCtx) {
+    SessionCatalog::get(_opCtx)->_disallowCheckoutsExceptForKilling();
+}
+
+ScopedBlockSessionCheckouts::~ScopedBlockSessionCheckouts() {
+    SessionCatalog::get(_opCtx)->_allowCheckouts();
+}
+
 }  // namespace mongo
diff --git a/src/mongo/db/session_catalog.h b/src/mongo/db/session_catalog.h
index 6841d85a6f6..7e30d62798e 100644
--- a/src/mongo/db/session_catalog.h
+++ b/src/mongo/db/session_catalog.h
@@ -46,6 +46,7 @@
 namespace mongo {
 
 class ObservableSession;
+class ScopedBlockSessionCheckouts;
 
 /**
  * Keeps track of the transaction runtime state for every active session on this instance.
@@ -116,6 +117,7 @@ public:
     size_t size() const;
 
 private:
+    friend ScopedBlockSessionCheckouts;
     struct SessionRuntimeInfo {
         SessionRuntimeInfo(LogicalSessionId lsid) : session(std::move(lsid)) {}
         ~SessionRuntimeInfo();
@@ -153,12 +155,27 @@ private:
      */
     void _releaseSession(SessionRuntimeInfo* sri, boost::optional<KillToken> killToken);
 
+    /**
+     * Disallow checkouts that are not for killing.
+     */
+    void _disallowCheckoutsExceptForKilling();
+
+    /**
+     * Re-enable checkouts if it was disallowed earlier.
+     */
+    void _allowCheckouts();
+
     // Protects the state below
     mutable Mutex _mutex =
         MONGO_MAKE_LATCH(HierarchicalAcquisitionLevel(0), "SessionCatalog::_mutex");
 
     // Owns the Session objects for all current Sessions.
     SessionRuntimeInfoMap _sessions;
+
+    // If false no new sessions can be checked out. Reasons why this could be true is because step
+    // down is in progress and we should not allow new sessions to get checked out in order to
+    // prevent deadlocks.
+    bool _checkoutAllowed{true};
 };
 
 /**
@@ -374,4 +391,19 @@ private:
     OperationContext* const _opCtx;
 };
 
+/**
+ * Scoped object, while active will prevent the checkout of sessions except for killing.
+ */
+class ScopedBlockSessionCheckouts {
+    ScopedBlockSessionCheckouts(const ScopedBlockSessionCheckouts&) = delete;
+    ScopedBlockSessionCheckouts& operator=(const ScopedBlockSessionCheckouts&) = delete;
+
+public:
+    ScopedBlockSessionCheckouts(OperationContext* opCtx);
+    ~ScopedBlockSessionCheckouts();
+
+private:
+    OperationContext* const _opCtx;
+};
+
 }  // namespace mongo