From b4db8c01a13fd70997a05857be17548b0adec020 Mon Sep 17 00:00:00 2001
From: Amirsaman Memaripour <amirsaman.memaripour@mongodb.com>
Date: Mon, 3 Aug 2020 14:56:59 +0000
Subject: SERVER-50064 Make recursion depth thread-local in ServiceExecutor
 tests

---
 src/mongo/transport/service_executor_fixed.cpp |  5 +++++
 src/mongo/transport/service_executor_fixed.h   |  6 ++++++
 src/mongo/transport/service_executor_test.cpp  | 19 +++----------------
 3 files changed, 14 insertions(+), 16 deletions(-)

diff --git a/src/mongo/transport/service_executor_fixed.cpp b/src/mongo/transport/service_executor_fixed.cpp
index abdd99ca586..495a59887d7 100644
--- a/src/mongo/transport/service_executor_fixed.cpp
+++ b/src/mongo/transport/service_executor_fixed.cpp
@@ -162,5 +162,10 @@ void ServiceExecutorFixed::appendStats(BSONObjBuilder* bob) const {
          << static_cast<int>(_numRunningExecutorThreads.load());
 }
 
+int ServiceExecutorFixed::getRecursionDepthForExecutorThread() const {
+    invariant(_executorContext);
+    return _executorContext->getRecursionDepth();
+}
+
 }  // namespace transport
 }  // namespace mongo
diff --git a/src/mongo/transport/service_executor_fixed.h b/src/mongo/transport/service_executor_fixed.h
index b7a90d43447..9aae4ab1718 100644
--- a/src/mongo/transport/service_executor_fixed.h
+++ b/src/mongo/transport/service_executor_fixed.h
@@ -67,6 +67,12 @@ public:
 
     void appendStats(BSONObjBuilder* bob) const override;
 
+    /**
+     * Returns the recursion depth of the active executor thread.
+     * It is forbidden to invoke this method outside scheduled tasks.
+     */
+    int getRecursionDepthForExecutorThread() const;
+
 private:
     // Maintains the execution state (e.g., recursion depth) for executor threads
     class ExecutorThreadContext {
diff --git a/src/mongo/transport/service_executor_test.cpp b/src/mongo/transport/service_executor_test.cpp
index c1d2b2b5f7e..608b0a09232 100644
--- a/src/mongo/transport/service_executor_test.cpp
+++ b/src/mongo/transport/service_executor_test.cpp
@@ -213,18 +213,6 @@ public:
         const bool _skipShutdown;
         std::shared_ptr<ServiceExecutorFixed> _executor;
     };
-
-    auto makeRecursionGuard() {
-        _recursionDepth.fetchAndAdd(1);
-        return makeGuard([this] { _recursionDepth.fetchAndSubtract(1); });
-    }
-
-    auto getRecursionDepth() const {
-        return _recursionDepth.load();
-    }
-
-private:
-    AtomicWord<int> _recursionDepth{0};
 };
 
 TEST_F(ServiceExecutorFixedFixture, ScheduleFailsBeforeStartup) {
@@ -251,8 +239,8 @@ TEST_F(ServiceExecutorFixedFixture, RecursiveTask) {
 
     std::function<void()> recursiveTask;
     recursiveTask = [&, barrier, executor = *executorHandle] {
-        auto recursionGuard = makeRecursionGuard();
-        if (getRecursionDepth() < fixedServiceExecutorRecursionLimit.load()) {
+        if (executor->getRecursionDepthForExecutorThread() <
+            fixedServiceExecutorRecursionLimit.load()) {
             ASSERT_OK(executor->scheduleTask(recursiveTask, ServiceExecutor::kMayRecurse));
         } else {
             // This test never returns unless the service executor can satisfy the recursion depth.
@@ -275,8 +263,7 @@ TEST_F(ServiceExecutorFixedFixture, FlattenRecursiveScheduledTasks) {
     // recursion depth remains zero during its execution.
     std::function<void()> recursiveTask;
     recursiveTask = [&, barrier, executor = *executorHandle] {
-        auto recursionGuard = makeRecursionGuard();
-        ASSERT_EQ(getRecursionDepth(), 1);
+        ASSERT_EQ(executor->getRecursionDepthForExecutorThread(), 1);
         if (tasksToSchedule.fetchAndSubtract(1) > 0) {
             ASSERT_OK(executor->scheduleTask(recursiveTask, ServiceExecutor::kEmptyFlags));
         } else {
-- 
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