SERVER-62404: Simplify mutex locking in fault_manager.cpp

(cherry picked from commit 14455a9ab66c529b140e777e29e49ba79e761814)

6 files changed, 27 insertions, 18 deletions

diff --git a/src/mongo/db/process_health/fault_manager.cpp b/src/mongo/db/process_health/fault_manager.cpp
index 1cc855e9b65..818eee320f2 100644
--- a/src/mongo/db/process_health/fault_manager.cpp
+++ b/src/mongo/db/process_health/fault_manager.cpp
@@ -90,7 +90,7 @@ void FaultManager::set(ServiceContext* svcCtx, std::unique_ptr<FaultManager> new
 
 
 bool FaultManager::isInitialized() {
-    stdx::lock_guard lock(_stateMutex);
+    stdx::lock_guard lock(_mutex);
     return _initialized;
 }
 
@@ -611,33 +611,38 @@ void FaultManager::updateWithCheckStatus(HealthCheckStatus&& checkStatus) {
         type, _svcCtx->getFastClockSource(), std::move(checkStatus)));
 }
 
-FaultManagerConfig FaultManager::getConfig() const {
+const FaultManagerConfig& FaultManager::getConfig() const {
     auto lk = stdx::lock_guard(_mutex);
     return *_config;
 }
 
 void FaultManager::_init() {
-    auto lk = stdx::lock_guard(_mutex);
+    std::set<FaultFacetType> allTypes;
+    std::vector<std::unique_ptr<HealthObserver>>::size_type observersSize = _observers.size();
+    {
+        auto lk = stdx::lock_guard(_mutex);
 
-    _observers = HealthObserverRegistration::instantiateAllObservers(_svcCtx);
+        _observers = HealthObserverRegistration::instantiateAllObservers(_svcCtx);
 
-    // Verify that all observer types are unique.
-    std::set<FaultFacetType> allTypes;
-    for (const auto& observer : _observers) {
-        allTypes.insert(observer->getType());
+        for (const auto& observer : _observers) {
+            allTypes.insert(observer->getType());
+        }
+        observersSize = _observers.size();
     }
-    invariant(allTypes.size() == _observers.size());
+
+    // Verify that all observer types are unique.
+    invariant(allTypes.size() == observersSize);
 
     // Start the monitor thread after all observers are initialized.
     _progressMonitor = std::make_unique<ProgressMonitor>(this, _svcCtx, _crashCb);
 
-    auto lk2 = stdx::lock_guard(_stateMutex);
     _initialized = true;
+
     LOGV2_DEBUG(5956701,
                 1,
                 "Instantiated health observers",
                 "managerState"_attr = str::stream() << state(),
-                "observersCount"_attr = _observers.size());
+                "observersCount"_attr = observersSize);
 }
 
 std::vector<HealthObserver*> FaultManager::getHealthObservers() const {
diff --git a/src/mongo/db/process_health/fault_manager.h b/src/mongo/db/process_health/fault_manager.h
index e53daefac86..4ef3a6c36e2 100644
--- a/src/mongo/db/process_health/fault_manager.h
+++ b/src/mongo/db/process_health/fault_manager.h
@@ -115,7 +115,7 @@ public:
     std::vector<HealthObserver*> getHealthObservers() const;
 
     // Gets the aggregate configuration for all process health environment.
-    FaultManagerConfig getConfig() const;
+    const FaultManagerConfig& getConfig() const;
 
     // Gets the timestamp of the last transition
     Date_t getLastTransitionTime() const;
diff --git a/src/mongo/db/process_health/fault_manager_config.h b/src/mongo/db/process_health/fault_manager_config.h
index f6d47bdbf24..072c304376c 100644
--- a/src/mongo/db/process_health/fault_manager_config.h
+++ b/src/mongo/db/process_health/fault_manager_config.h
@@ -133,6 +133,7 @@ public:
             } else {
                 // TODO SERVER-61944: this is for kMock1 & kMock2. Remove this branch once mock
                 // types are deleted.
+                stdx::lock_guard lock(_mutex);
                 if (_facetToIntensityMapForTest.contains(type)) {
                     return _facetToIntensityMapForTest.at(type);
                 }
@@ -143,11 +144,12 @@ public:
         return getIntensity(type);
     }
 
-    bool isHealthObserverEnabled(FaultFacetType type) {
+    bool isHealthObserverEnabled(FaultFacetType type) const {
         return getHealthObserverIntensity(type) != HealthObserverIntensityEnum::kOff;
     }
 
     void setIntensityForType(FaultFacetType type, HealthObserverIntensityEnum intensity) {
+        stdx::lock_guard lock(_mutex);
         _facetToIntensityMapForTest.insert({type, intensity});
     }
 
@@ -245,6 +247,8 @@ private:
     bool _periodicChecksDisabledForTests = false;
 
     stdx::unordered_map<FaultFacetType, HealthObserverIntensityEnum> _facetToIntensityMapForTest;
+    mutable Mutex _mutex =
+        MONGO_MAKE_LATCH(HierarchicalAcquisitionLevel(5), "FaultManagerConfig::_mutex");
 };
 
 }  // namespace process_health
diff --git a/src/mongo/db/process_health/fault_manager_test.cpp b/src/mongo/db/process_health/fault_manager_test.cpp
index e3466699906..f57f6b869b7 100644
--- a/src/mongo/db/process_health/fault_manager_test.cpp
+++ b/src/mongo/db/process_health/fault_manager_test.cpp
@@ -48,7 +48,7 @@ TEST(FaultManagerTest, Registration) {
 
 // Tests the default health observer intensity of non-critical
 TEST_F(FaultManagerTest, GetHealthObserverIntensity) {
-    auto config = manager().getConfig();
+    auto& config = manager().getConfig();
     ASSERT(config.getHealthObserverIntensity(FaultFacetType::kLdap) ==
            HealthObserverIntensityEnum::kOff);
     ASSERT(config.getHealthObserverIntensity(FaultFacetType::kDns) ==
diff --git a/src/mongo/db/process_health/fault_manager_test_suite.h b/src/mongo/db/process_health/fault_manager_test_suite.h
index 62332ffb235..d8320e4249b 100644
--- a/src/mongo/db/process_health/fault_manager_test_suite.h
+++ b/src/mongo/db/process_health/fault_manager_test_suite.h
@@ -106,7 +106,7 @@ public:
         progressMonitorCheckForTests(crashCb);
     }
 
-    FaultManagerConfig getConfigTest() {
+    const FaultManagerConfig& getConfigTest() {
         return getConfig();
     }
 
diff --git a/src/mongo/db/process_health/health_observer_test.cpp b/src/mongo/db/process_health/health_observer_test.cpp
index 6937f5a70c1..5725fb5b8c0 100644
--- a/src/mongo/db/process_health/health_observer_test.cpp
+++ b/src/mongo/db/process_health/health_observer_test.cpp
@@ -144,15 +144,15 @@ TEST_F(FaultManagerTest, HealthCheckRunsPeriodically) {
                                          << "interval" << 1)))};
     RAIIServerParameterControllerForTest _controller{"featureFlagHealthMonitoring", true};
     auto faultFacetType = FaultFacetType::kMock1;
-    auto severity = Severity::kOk;
-    registerMockHealthObserver(faultFacetType, [&severity] { return severity; });
+    AtomicWord<Severity> severity{Severity::kOk};
+    registerMockHealthObserver(faultFacetType, [&severity] { return severity.load(); });
 
     assertSoon([this] { return (manager().getFaultState() == FaultState::kStartupCheck); });
 
     auto initialHealthCheckFuture = manager().startPeriodicHealthChecks();
     assertSoon([this] { return (manager().getFaultState() == FaultState::kOk); });
 
-    severity = Severity::kFailure;
+    severity.store(Severity::kFailure);
     assertSoon([this] { return (manager().getFaultState() == FaultState::kTransientFault); });
     resetManager();  // Before fields above go out of scope.
 }