worker: use rwlock for sibling group

Since it is much more common to send messages than to add or remove ports from a sibling group, using a rwlock is appropriate here. Refs: #38780 (comment) PR-URL: #38783 Reviewed-By: James M Snell <[email protected]> Reviewed-By: Joyee Cheung <[email protected]>

Author: addaleax

src/node_messaging.cc

@@ -1331,7 +1331,7 @@ Maybe<bool> SiblingGroup::Dispatch(
  std::shared_ptr<Message> message,
  std::string* error){
 
-Mutex::ScopedLocklock(group_mutex_);
+RwLock::ScopedReadLocklock(group_mutex_);
 
 // The source MessagePortData is not part of this group.
 if (ports_.find(source) == ports_.end()){
@@ -1376,7 +1376,7 @@ void SiblingGroup::Entangle(MessagePortData* port){
 }
 
 voidSiblingGroup::Entangle(std::initializer_list<MessagePortData*> ports){
-Mutex::ScopedLocklock(group_mutex_);
+RwLock::ScopedWriteLocklock(group_mutex_);
 for (MessagePortData* data : ports){
  ports_.insert(data);
 CHECK(!data->group_);
@@ -1386,7 +1386,7 @@ void SiblingGroup::Entangle(std::initializer_list<MessagePortData*> ports){
 
 voidSiblingGroup::Disentangle(MessagePortData* data){
 auto self = shared_from_this(); // Keep alive until end of function.
-Mutex::ScopedLocklock(group_mutex_);
+RwLock::ScopedWriteLocklock(group_mutex_);
  ports_.erase(data);
  data->group_.reset();
 

src/node_messaging.h

@@ -150,9 +150,9 @@ class SiblingGroup final : public std::enable_shared_from_this<SiblingGroup>{
 size_tsize() const{return ports_.size()}
 
 private:
- std::string name_;
+const std::string name_;
+ RwLock group_mutex_; // Protects ports_.
  std::set<MessagePortData*> ports_;
- Mutex group_mutex_;
 
 staticvoidCheckSiblingGroup(const std::string& name);
 

src/node_mutex.h

@@ -14,9 +14,11 @@ namespace node{
 template <typename Traits> classConditionVariableBase;
 template <typename Traits> classMutexBase;
 structLibuvMutexTraits;
+structLibuvRwlockTraits;
 
 using ConditionVariable = ConditionVariableBase<LibuvMutexTraits>
 using Mutex = MutexBase<LibuvMutexTraits>
+using RwLock = MutexBase<LibuvRwlockTraits>
 
 template <typename T, typename MutexT = Mutex>
 classExclusiveAccess{
@@ -70,6 +72,8 @@ class MutexBase{
 inline~MutexBase();
 inlinevoidLock();
 inlinevoidUnlock();
+inlinevoidRdLock();
+inlinevoidRdUnlock();
 
 MutexBase(const MutexBase&) = delete;
  MutexBase& operator=(const MutexBase&) = delete;
@@ -92,6 +96,21 @@ class MutexBase{
 const MutexBase& mutex_;
  };
 
+classScopedReadLock{
+public:
+inlineexplicitScopedReadLock(const MutexBase& mutex);
+inline~ScopedReadLock();
+
+ScopedReadLock(const ScopedReadLock&) = delete;
+ ScopedReadLock& operator=(const ScopedReadLock&) = delete;
+
+private:
+template <typename> friendclassConditionVariableBase;
+const MutexBase& mutex_;
+ };
+
+using ScopedWriteLock = ScopedLock;
+
 classScopedUnlock{
 public:
 inlineexplicitScopedUnlock(const ScopedLock& scoped_lock);
@@ -167,6 +186,42 @@ struct LibuvMutexTraits{
 staticinlinevoidmutex_unlock(MutexT* mutex){
 uv_mutex_unlock(mutex);
  }
+
+staticinlinevoidmutex_rdlock(MutexT* mutex){
+uv_mutex_lock(mutex);
+ }
+
+staticinlinevoidmutex_rdunlock(MutexT* mutex){
+uv_mutex_unlock(mutex);
+ }
+};
+
+structLibuvRwlockTraits{
+using MutexT = uv_rwlock_t;
+
+staticinlineintmutex_init(MutexT* mutex){
+returnuv_rwlock_init(mutex);
+ }
+
+staticinlinevoidmutex_destroy(MutexT* mutex){
+uv_rwlock_destroy(mutex);
+ }
+
+staticinlinevoidmutex_lock(MutexT* mutex){
+uv_rwlock_wrlock(mutex);
+ }
+
+staticinlinevoidmutex_unlock(MutexT* mutex){
+uv_rwlock_wrunlock(mutex);
+ }
+
+staticinlinevoidmutex_rdlock(MutexT* mutex){
+uv_rwlock_rdlock(mutex);
+ }
+
+staticinlinevoidmutex_rdunlock(MutexT* mutex){
+uv_rwlock_rdunlock(mutex);
+ }
 };
 
 template <typename Traits>
@@ -214,6 +269,16 @@ void MutexBase<Traits>::Unlock(){
 Traits::mutex_unlock(&mutex_);
 }
 
+template <typename Traits>
+void MutexBase<Traits>::RdLock(){
+Traits::mutex_rdlock(&mutex_);
+}
+
+template <typename Traits>
+void MutexBase<Traits>::RdUnlock(){
+Traits::mutex_rdunlock(&mutex_);
+}
+
 template <typename Traits>
 MutexBase<Traits>::ScopedLock::ScopedLock(const MutexBase& mutex)
  : mutex_(mutex){
@@ -229,6 +294,17 @@ MutexBase<Traits>::ScopedLock::~ScopedLock(){
 Traits::mutex_unlock(&mutex_.mutex_);
 }
 
+template <typename Traits>
+MutexBase<Traits>::ScopedReadLock::ScopedReadLock(const MutexBase& mutex)
+ : mutex_(mutex){
+Traits::mutex_rdlock(&mutex_.mutex_);
+}
+
+template <typename Traits>
+MutexBase<Traits>::ScopedReadLock::~ScopedReadLock(){
+Traits::mutex_rdunlock(&mutex_.mutex_);
+}
+
 template <typename Traits>
 MutexBase<Traits>::ScopedUnlock::ScopedUnlock(const ScopedLock& scoped_lock)
  : mutex_(scoped_lock.mutex_){