SERVER-25694 Eliminate race in PlanExecutor cleanup.

Ensures that a collection lock is held in at least MODE_IS while
deregistering a PlanExecutor from the cursor manager. Introduces new
PlanExecutor::dispose() and ClientCursor::dispose() methods that must be
called before destruction of those classes, and ensures they are called
before destruction. These calls will thread an OperationContext all the
way through to DocumentSource::dispose() for each stage in a Pipeline,
which will give DocumentSourceCursor a chance to acquire locks and
deregister its PlanExecutor if necessary.

1 files changed, 2 insertions, 2 deletions

diff --git a/src/mongo/db/s/migration_chunk_cloner_source_legacy.h b/src/mongo/db/s/migration_chunk_cloner_source_legacy.h
index 7f8b7bf5468..28eca3989c5 100644
--- a/src/mongo/db/s/migration_chunk_cloner_source_legacy.h
+++ b/src/mongo/db/s/migration_chunk_cloner_source_legacy.h
@@ -34,6 +34,7 @@
 #include "mongo/bson/bsonobj.h"
 #include "mongo/client/connection_string.h"
 #include "mongo/db/namespace_string.h"
+#include "mongo/db/query/plan_executor.h"
 #include "mongo/db/s/migration_chunk_cloner_source.h"
 #include "mongo/db/s/migration_session_id.h"
 #include "mongo/s/move_chunk_request.h"
@@ -48,7 +49,6 @@ class BSONArrayBuilder;
 class BSONObjBuilder;
 class Collection;
 class Database;
-class PlanExecutor;
 class RecordId;
 
 class MigrationChunkClonerSourceLegacy final : public MigrationChunkClonerSource {
@@ -181,7 +181,7 @@ private:
 
     // Registered deletion notifications plan executor, which will listen for document deletions
     // during the cloning stage
-    std::unique_ptr<PlanExecutor> _deleteNotifyExec;
+    std::unique_ptr<PlanExecutor, PlanExecutor::Deleter> _deleteNotifyExec;
 
     // Protects the entries below
     stdx::mutex _mutex;