3 files changed, 8 insertions, 7 deletions
diff --git a/openjdkjvmti/events-inl.h b/openjdkjvmti/events-inl.h
index 007669b50f..74ffb84579 100644
--- a/openjdkjvmti/events-inl.h
+++ b/openjdkjvmti/events-inl.h
@@ -187,7 +187,7 @@ FORALL_EVENT_TYPES(MAKE_EVENT_HANDLER_FUNC)
 template <ArtJvmtiEvent kEvent, typename ...Args>
 inline std::vector<impl::EventHandlerFunc<kEvent>> EventHandler::CollectEvents(art::Thread* thread,
                                                                                Args... args) const {
-  art::MutexLock mu(thread, envs_lock_);
+  art::ReaderMutexLock mu(thread, envs_lock_);
   std::vector<impl::EventHandlerFunc<kEvent>> handlers;
   for (ArtJvmTiEnv* env : envs) {
     if (ShouldDispatch<kEvent>(env, thread, args...)) {
@@ -527,7 +527,7 @@ inline bool EventHandler::ShouldDispatch(ArtJvmTiEnv* env,
 }
 
 inline void EventHandler::RecalculateGlobalEventMask(ArtJvmtiEvent event) {
-  art::MutexLock mu(art::Thread::Current(), envs_lock_);
+  art::WriterMutexLock mu(art::Thread::Current(), envs_lock_);
   RecalculateGlobalEventMaskLocked(event);
 }
 
diff --git a/openjdkjvmti/events.cc b/openjdkjvmti/events.cc
index d98fda5f9c..62b73c08c0 100644
--- a/openjdkjvmti/events.cc
+++ b/openjdkjvmti/events.cc
@@ -196,12 +196,12 @@ void EventMasks::HandleChangedCapabilities(const jvmtiCapabilities& caps, bool c
 }
 
 void EventHandler::RegisterArtJvmTiEnv(ArtJvmTiEnv* env) {
-  art::MutexLock mu(art::Thread::Current(), envs_lock_);
+  art::WriterMutexLock mu(art::Thread::Current(), envs_lock_);
   envs.push_back(env);
 }
 
 void EventHandler::RemoveArtJvmTiEnv(ArtJvmTiEnv* env) {
-  art::MutexLock mu(art::Thread::Current(), envs_lock_);
+  art::WriterMutexLock mu(art::Thread::Current(), envs_lock_);
   // Since we might be currently iterating over the envs list we cannot actually erase elements.
   // Instead we will simply replace them with 'nullptr' and skip them manually.
   auto it = std::find(envs.begin(), envs.end(), env);
@@ -1143,7 +1143,7 @@ jvmtiError EventHandler::SetEvent(ArtJvmTiEnv* env,
   {
     // Change the event masks atomically.
     art::Thread* self = art::Thread::Current();
-    art::MutexLock mu(self, envs_lock_);
+    art::WriterMutexLock mu(self, envs_lock_);
     art::WriterMutexLock mu_env_info(self, env->event_info_mutex_);
     old_state = global_mask.Test(event);
     if (mode == JVMTI_ENABLE) {
diff --git a/openjdkjvmti/events.h b/openjdkjvmti/events.h
index 81edb931cd..8141eff88c 100644
--- a/openjdkjvmti/events.h
+++ b/openjdkjvmti/events.h
@@ -283,7 +283,7 @@ class EventHandler {
   ALWAYS_INLINE
   inline void RecalculateGlobalEventMask(ArtJvmtiEvent event) REQUIRES(!envs_lock_);
   ALWAYS_INLINE
-  inline void RecalculateGlobalEventMaskLocked(ArtJvmtiEvent event) REQUIRES(envs_lock_);
+  inline void RecalculateGlobalEventMaskLocked(ArtJvmtiEvent event) REQUIRES_SHARED(envs_lock_);
 
   template <ArtJvmtiEvent kEvent>
   ALWAYS_INLINE inline void DispatchClassFileLoadHookEvent(art::Thread* thread,
@@ -310,7 +310,8 @@ class EventHandler {
   std::list<ArtJvmTiEnv*> envs GUARDED_BY(envs_lock_);
 
   // Top level lock. Nothing at all should be held when we lock this.
-  mutable art::Mutex envs_lock_ ACQUIRED_BEFORE(art::Locks::instrument_entrypoints_lock_);
+  mutable art::ReaderWriterMutex envs_lock_
+      ACQUIRED_BEFORE(art::Locks::instrument_entrypoints_lock_);
 
   // A union of all enabled events, anywhere.
   EventMask global_mask;