SERVER-43701 Fix race condition between endBackup and cleanShutdown

3 files changed, 14 insertions, 0 deletions

diff --git a/src/mongo/db/storage/wiredtiger/wiredtiger_kv_engine.cpp b/src/mongo/db/storage/wiredtiger/wiredtiger_kv_engine.cpp
index e6daab5e98c..ae7e620290c 100644
--- a/src/mongo/db/storage/wiredtiger/wiredtiger_kv_engine.cpp
+++ b/src/mongo/db/storage/wiredtiger/wiredtiger_kv_engine.cpp
@@ -1059,6 +1059,10 @@ Status WiredTigerKVEngine::beginBackup(OperationContext* opCtx) {
 }
 
 void WiredTigerKVEngine::endBackup(OperationContext* opCtx) {
+    if (_sessionCache->isShuttingDown()) {
+        // There could be a race with clean shutdown which unconditionally closes all the sessions.
+        _backupSession->_session = nullptr;  // Prevent calling _session->close() in destructor.
+    }
     _backupSession.reset();
 }
 
diff --git a/src/mongo/db/storage/wiredtiger/wiredtiger_session_cache.cpp b/src/mongo/db/storage/wiredtiger/wiredtiger_session_cache.cpp
index 8b56cf66ec9..cf04a16d550 100644
--- a/src/mongo/db/storage/wiredtiger/wiredtiger_session_cache.cpp
+++ b/src/mongo/db/storage/wiredtiger/wiredtiger_session_cache.cpp
@@ -235,6 +235,10 @@ void WiredTigerSessionCache::shuttingDown() {
     closeAll();
 }
 
+bool WiredTigerSessionCache::isShuttingDown() {
+    return _shuttingDown.load() & kShuttingDownMask;
+}
+
 void WiredTigerSessionCache::waitUntilDurable(OperationContext* opCtx,
                                               bool forceCheckpoint,
                                               bool stableCheckpoint) {
diff --git a/src/mongo/db/storage/wiredtiger/wiredtiger_session_cache.h b/src/mongo/db/storage/wiredtiger/wiredtiger_session_cache.h
index 3cd9b974010..e2d0ce3b2e0 100644
--- a/src/mongo/db/storage/wiredtiger/wiredtiger_session_cache.h
+++ b/src/mongo/db/storage/wiredtiger/wiredtiger_session_cache.h
@@ -175,6 +175,7 @@ public:
 
 private:
     friend class WiredTigerSessionCache;
+    friend class WiredTigerKVEngine;
 
     // The cursor cache is a list of pairs that contain an ID and cursor
     typedef std::list<WiredTigerCachedCursor> CursorCache;
@@ -264,6 +265,11 @@ public:
      */
     void shuttingDown();
 
+    /**
+     * True when in the process of shutting down.
+     */
+    bool isShuttingDown();
+
     bool isEphemeral();
 
     /**