From 4fe8b13a8e604bb232bb3ce7b4be045d94b81d44 Mon Sep 17 00:00:00 2001
From: Niels Dekker <N.Dekker@lumc.nl>
Date: Wed, 23 Aug 2023 13:50:33 +0200
Subject: [PATCH] STYLE: Replace `std::unique_lock` with `std::lock_guard` in
 ThreadPool

A `std::lock_guard` is more lightweight than a `std::unique_lock`, so for
simple use cases, `std::lock_guard` appears preferable.
---
 Modules/Core/Common/include/itkThreadPool.h | 4 ++--
 Modules/Core/Common/src/itkThreadPool.cxx   | 6 +++---
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/Modules/Core/Common/include/itkThreadPool.h b/Modules/Core/Common/include/itkThreadPool.h
index ca0be924e8b..821fbd257d8 100644
--- a/Modules/Core/Common/include/itkThreadPool.h
+++ b/Modules/Core/Common/include/itkThreadPool.h
@@ -93,7 +93,7 @@ auto result = pool->AddWork([](int param) { return param; }, 7);
 
     std::future<return_type> res = task->get_future();
     {
-      std::unique_lock<std::mutex> lock(this->GetMutex());
+      const std::lock_guard<std::mutex> lockGuard(this->GetMutex());
       m_WorkQueue.emplace_back([task]() { (*task)(); });
     }
     m_Condition.notify_one();
@@ -107,7 +107,7 @@ auto result = pool->AddWork([](int param) { return param; }, 7);
   ThreadIdType
   GetMaximumNumberOfThreads() const
   {
-    std::unique_lock<std::mutex> lock(this->GetMutex());
+    const std::lock_guard<std::mutex> lockGuard(this->GetMutex());
     return static_cast<ThreadIdType>(m_Threads.size());
   }
 
diff --git a/Modules/Core/Common/src/itkThreadPool.cxx b/Modules/Core/Common/src/itkThreadPool.cxx
index dfcfc6164ca..57065659fa3 100644
--- a/Modules/Core/Common/src/itkThreadPool.cxx
+++ b/Modules/Core/Common/src/itkThreadPool.cxx
@@ -122,7 +122,7 @@ ThreadPool::ThreadPool()
 void
 ThreadPool::AddThreads(ThreadIdType count)
 {
-  std::unique_lock<std::mutex> mutexHolder(m_PimplGlobals->m_Mutex);
+  const std::lock_guard<std::mutex> lockGuard(m_PimplGlobals->m_Mutex);
   m_Threads.reserve(m_Threads.size() + count);
   for (ThreadIdType i = 0; i < count; ++i)
   {
@@ -139,7 +139,7 @@ ThreadPool::GetMutex() const
 int
 ThreadPool::GetNumberOfCurrentlyIdleThreads() const
 {
-  std::unique_lock<std::mutex> mutexHolder(m_PimplGlobals->m_Mutex);
+  const std::lock_guard<std::mutex> lockGuard(m_PimplGlobals->m_Mutex);
   return static_cast<int>(m_Threads.size()) - static_cast<int>(m_WorkQueue.size()); // lousy approximation
 }
 
@@ -148,7 +148,7 @@ ThreadPool::CleanUp()
 {
   bool shouldNotify;
   {
-    std::unique_lock<std::mutex> mutexHolder(m_PimplGlobals->m_Mutex);
+    const std::lock_guard<std::mutex> lockGuard(m_PimplGlobals->m_Mutex);
 
     this->m_Stopping = true;