vendor/llvm-project/llvmorg-11-init-20887-g2e10b7a39b9vendor/llvm-project/master

1 files changed, 18 insertions, 28 deletions

diff --git a/llvm/lib/Support/ThreadPool.cpp b/llvm/lib/Support/ThreadPool.cpp
index 40982d777914..46a1990cd719 100644
--- a/llvm/lib/Support/ThreadPool.cpp
+++ b/llvm/lib/Support/ThreadPool.cpp
@@ -20,16 +20,14 @@ using namespace llvm;
 
 #if LLVM_ENABLE_THREADS
 
-// Default to hardware_concurrency
-ThreadPool::ThreadPool() : ThreadPool(hardware_concurrency()) {}
-
-ThreadPool::ThreadPool(unsigned ThreadCount)
-    : ActiveThreads(0), EnableFlag(true) {
+ThreadPool::ThreadPool(ThreadPoolStrategy S)
+    : ThreadCount(S.compute_thread_count()) {
   // Create ThreadCount threads that will loop forever, wait on QueueCondition
   // for tasks to be queued or the Pool to be destroyed.
   Threads.reserve(ThreadCount);
   for (unsigned ThreadID = 0; ThreadID < ThreadCount; ++ThreadID) {
-    Threads.emplace_back([&] {
+    Threads.emplace_back([S, ThreadID, this] {
+      S.apply_thread_strategy(ThreadID);
       while (true) {
         PackagedTaskTy Task;
         {
@@ -45,24 +43,24 @@ ThreadPool::ThreadPool(unsigned ThreadCount)
           // We first need to signal that we are active before popping the queue
           // in order for wait() to properly detect that even if the queue is
           // empty, there is still a task in flight.
-          {
-            std::unique_lock<std::mutex> LockGuard(CompletionLock);
-            ++ActiveThreads;
-          }
+          ++ActiveThreads;
           Task = std::move(Tasks.front());
           Tasks.pop();
         }
         // Run the task we just grabbed
         Task();
 
+        bool Notify;
         {
           // Adjust `ActiveThreads`, in case someone waits on ThreadPool::wait()
-          std::unique_lock<std::mutex> LockGuard(CompletionLock);
+          std::lock_guard<std::mutex> LockGuard(QueueLock);
           --ActiveThreads;
+          Notify = workCompletedUnlocked();
         }
-
-        // Notify task completion, in case someone waits on ThreadPool::wait()
-        CompletionCondition.notify_all();
+        // Notify task completion if this is the last active thread, in case
+        // someone waits on ThreadPool::wait().
+        if (Notify)
+          CompletionCondition.notify_all();
       }
     });
   }
@@ -70,12 +68,8 @@ ThreadPool::ThreadPool(unsigned ThreadCount)
 
 void ThreadPool::wait() {
   // Wait for all threads to complete and the queue to be empty
-  std::unique_lock<std::mutex> LockGuard(CompletionLock);
-  // The order of the checks for ActiveThreads and Tasks.empty() matters because
-  // any active threads might be modifying the Tasks queue, and this would be a
-  // race.
-  CompletionCondition.wait(LockGuard,
-                           [&] { return !ActiveThreads && Tasks.empty(); });
+  std::unique_lock<std::mutex> LockGuard(QueueLock);
+  CompletionCondition.wait(LockGuard, [&] { return workCompletedUnlocked(); });
 }
 
 std::shared_future<void> ThreadPool::asyncImpl(TaskTy Task) {
@@ -108,12 +102,10 @@ ThreadPool::~ThreadPool() {
 
 #else // LLVM_ENABLE_THREADS Disabled
 
-ThreadPool::ThreadPool() : ThreadPool(0) {}
-
 // No threads are launched, issue a warning if ThreadCount is not 0
-ThreadPool::ThreadPool(unsigned ThreadCount)
-    : ActiveThreads(0) {
-  if (ThreadCount) {
+ThreadPool::ThreadPool(ThreadPoolStrategy S)
+    : ThreadCount(S.compute_thread_count()) {
+  if (ThreadCount != 1) {
     errs() << "Warning: request a ThreadPool with " << ThreadCount
            << " threads, but LLVM_ENABLE_THREADS has been turned off\n";
   }
@@ -138,8 +130,6 @@ std::shared_future<void> ThreadPool::asyncImpl(TaskTy Task) {
   return Future;
 }
 
-ThreadPool::~ThreadPool() {
-  wait();
-}
+ThreadPool::~ThreadPool() { wait(); }
 
 #endif