1 files changed, 18 insertions, 0 deletions
diff --git a/src/mongo/db/catalog/apply_ops.cpp b/src/mongo/db/catalog/apply_ops.cpp
index 9118c2b6d18..92c2be22772 100644
--- a/src/mongo/db/catalog/apply_ops.cpp
+++ b/src/mongo/db/catalog/apply_ops.cpp
@@ -50,10 +50,15 @@
 #include "mongo/db/repl/oplog.h"
 #include "mongo/db/repl/replication_coordinator_global.h"
 #include "mongo/db/service_context.h"
+#include "mongo/util/fail_point_service.h"
 #include "mongo/util/log.h"
 
 namespace mongo {
 namespace {
+
+// If enabled, causes loop in _applyOps() to hang after applying current operation.
+MONGO_FP_DECLARE(applyOpsPauseBetweenOperations);
+
 /**
  * Return true iff the applyOpsCmd can be executed in a single WriteUnitOfWork.
  */
@@ -198,6 +203,19 @@ Status _applyOps(OperationContext* opCtx,
             }
 
             (*numApplied)++;
+
+            if (MONGO_FAIL_POINT(applyOpsPauseBetweenOperations)) {
+                // While holding a database lock under MMAPv1, we would be implicitly holding the
+                // flush lock here. This would prevent other threads from acquiring the global
+                // lock or any database locks. We release all locks temporarily while the fail
+                // point is enabled to allow other threads to make progress.
+                boost::optional<Lock::TempRelease> release;
+                auto storageEngine = opCtx->getServiceContext()->getGlobalStorageEngine();
+                if (storageEngine->isMmapV1() && !opCtx->lockState()->isW()) {
+                    release.emplace(opCtx->lockState());
+                }
+                MONGO_FAIL_POINT_PAUSE_WHILE_SET(applyOpsPauseBetweenOperations);
+            }
         }
 
         result->append("applied", *numApplied);