1 files changed, 131 insertions, 40 deletions

diff --git a/contrib/llvm-project/llvm/lib/Support/ThreadPool.cpp b/contrib/llvm-project/llvm/lib/Support/ThreadPool.cpp
index 9f92ae1c7a7c..31461e31c65c 100644
--- a/contrib/llvm-project/llvm/lib/Support/ThreadPool.cpp
+++ b/contrib/llvm-project/llvm/lib/Support/ThreadPool.cpp
@@ -24,11 +24,19 @@ using namespace llvm;
 
 #if LLVM_ENABLE_THREADS
 
+// A note on thread groups: Tasks are by default in no group (represented
+// by nullptr ThreadPoolTaskGroup pointer in the Tasks queue) and functionality
+// here normally works on all tasks regardless of their group (functions
+// in that case receive nullptr ThreadPoolTaskGroup pointer as argument).
+// A task in a group has a pointer to that ThreadPoolTaskGroup in the Tasks
+// queue, and functions called to work only on tasks from one group take that
+// pointer.
+
 ThreadPool::ThreadPool(ThreadPoolStrategy S)
     : Strategy(S), MaxThreadCount(S.compute_thread_count()) {}
 
 void ThreadPool::grow(int requested) {
-  std::unique_lock<std::mutex> LockGuard(ThreadsLock);
+  llvm::sys::ScopedWriter LockGuard(ThreadsLock);
   if (Threads.size() >= MaxThreadCount)
     return; // Already hit the max thread pool size.
   int newThreadCount = std::min<int>(requested, MaxThreadCount);
@@ -36,52 +44,129 @@ void ThreadPool::grow(int requested) {
     int ThreadID = Threads.size();
     Threads.emplace_back([this, ThreadID] {
       Strategy.apply_thread_strategy(ThreadID);
-      while (true) {
-        std::function<void()> Task;
-        {
-          std::unique_lock<std::mutex> LockGuard(QueueLock);
-          // Wait for tasks to be pushed in the queue
-          QueueCondition.wait(LockGuard,
-                              [&] { return !EnableFlag || !Tasks.empty(); });
-          // Exit condition
-          if (!EnableFlag && Tasks.empty())
-            return;
-          // Yeah, we have a task, grab it and release the lock on the queue
-
-          // 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.
-          ++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::lock_guard<std::mutex> LockGuard(QueueLock);
-          --ActiveThreads;
-          Notify = workCompletedUnlocked();
-        }
-        // Notify task completion if this is the last active thread, in case
-        // someone waits on ThreadPool::wait().
-        if (Notify)
-          CompletionCondition.notify_all();
-      }
+      processTasks(nullptr);
     });
   }
 }
 
+#ifndef NDEBUG
+// The group of the tasks run by the current thread.
+static LLVM_THREAD_LOCAL std::vector<ThreadPoolTaskGroup *>
+    *CurrentThreadTaskGroups = nullptr;
+#endif
+
+// WaitingForGroup == nullptr means all tasks regardless of their group.
+void ThreadPool::processTasks(ThreadPoolTaskGroup *WaitingForGroup) {
+  while (true) {
+    std::function<void()> Task;
+    ThreadPoolTaskGroup *GroupOfTask;
+    {
+      std::unique_lock<std::mutex> LockGuard(QueueLock);
+      bool workCompletedForGroup = false; // Result of workCompletedUnlocked()
+      // Wait for tasks to be pushed in the queue
+      QueueCondition.wait(LockGuard, [&] {
+        return !EnableFlag || !Tasks.empty() ||
+               (WaitingForGroup != nullptr &&
+                (workCompletedForGroup =
+                     workCompletedUnlocked(WaitingForGroup)));
+      });
+      // Exit condition
+      if (!EnableFlag && Tasks.empty())
+        return;
+      if (WaitingForGroup != nullptr && workCompletedForGroup)
+        return;
+      // Yeah, we have a task, grab it and release the lock on the queue
+
+      // 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.
+      ++ActiveThreads;
+      Task = std::move(Tasks.front().first);
+      GroupOfTask = Tasks.front().second;
+      // Need to count active threads in each group separately, ActiveThreads
+      // would never be 0 if waiting for another group inside a wait.
+      if (GroupOfTask != nullptr)
+        ++ActiveGroups[GroupOfTask]; // Increment or set to 1 if new item
+      Tasks.pop_front();
+    }
+#ifndef NDEBUG
+    if (CurrentThreadTaskGroups == nullptr)
+      CurrentThreadTaskGroups = new std::vector<ThreadPoolTaskGroup *>;
+    CurrentThreadTaskGroups->push_back(GroupOfTask);
+#endif
+
+    // Run the task we just grabbed
+    Task();
+
+#ifndef NDEBUG
+    CurrentThreadTaskGroups->pop_back();
+    if (CurrentThreadTaskGroups->empty()) {
+      delete CurrentThreadTaskGroups;
+      CurrentThreadTaskGroups = nullptr;
+    }
+#endif
+
+    bool Notify;
+    bool NotifyGroup;
+    {
+      // Adjust `ActiveThreads`, in case someone waits on ThreadPool::wait()
+      std::lock_guard<std::mutex> LockGuard(QueueLock);
+      --ActiveThreads;
+      if (GroupOfTask != nullptr) {
+        auto A = ActiveGroups.find(GroupOfTask);
+        if (--(A->second) == 0)
+          ActiveGroups.erase(A);
+      }
+      Notify = workCompletedUnlocked(GroupOfTask);
+      NotifyGroup = GroupOfTask != nullptr && Notify;
+    }
+    // Notify task completion if this is the last active thread, in case
+    // someone waits on ThreadPool::wait().
+    if (Notify)
+      CompletionCondition.notify_all();
+    // If this was a task in a group, notify also threads waiting for tasks
+    // in this function on QueueCondition, to make a recursive wait() return
+    // after the group it's been waiting for has finished.
+    if (NotifyGroup)
+      QueueCondition.notify_all();
+  }
+}
+
+bool ThreadPool::workCompletedUnlocked(ThreadPoolTaskGroup *Group) const {
+  if (Group == nullptr)
+    return !ActiveThreads && Tasks.empty();
+  return ActiveGroups.count(Group) == 0 &&
+         !llvm::any_of(Tasks,
+                       [Group](const auto &T) { return T.second == Group; });
+}
+
 void ThreadPool::wait() {
+  assert(!isWorkerThread()); // Would deadlock waiting for itself.
   // Wait for all threads to complete and the queue to be empty
   std::unique_lock<std::mutex> LockGuard(QueueLock);
-  CompletionCondition.wait(LockGuard, [&] { return workCompletedUnlocked(); });
+  CompletionCondition.wait(LockGuard,
+                           [&] { return workCompletedUnlocked(nullptr); });
+}
+
+void ThreadPool::wait(ThreadPoolTaskGroup &Group) {
+  // Wait for all threads in the group to complete.
+  if (!isWorkerThread()) {
+    std::unique_lock<std::mutex> LockGuard(QueueLock);
+    CompletionCondition.wait(LockGuard,
+                             [&] { return workCompletedUnlocked(&Group); });
+    return;
+  }
+  // Make sure to not deadlock waiting for oneself.
+  assert(CurrentThreadTaskGroups == nullptr ||
+         !llvm::is_contained(*CurrentThreadTaskGroups, &Group));
+  // Handle the case of recursive call from another task in a different group,
+  // in which case process tasks while waiting to keep the thread busy and avoid
+  // possible deadlock.
+  processTasks(&Group);
 }
 
 bool ThreadPool::isWorkerThread() const {
-  std::unique_lock<std::mutex> LockGuard(ThreadsLock);
+  llvm::sys::ScopedReader LockGuard(ThreadsLock);
   llvm::thread::id CurrentThreadId = llvm::this_thread::get_id();
   for (const llvm::thread &Thread : Threads)
     if (CurrentThreadId == Thread.get_id())
@@ -96,7 +181,7 @@ ThreadPool::~ThreadPool() {
     EnableFlag = false;
   }
   QueueCondition.notify_all();
-  std::unique_lock<std::mutex> LockGuard(ThreadsLock);
+  llvm::sys::ScopedReader LockGuard(ThreadsLock);
   for (auto &Worker : Threads)
     Worker.join();
 }
@@ -115,12 +200,18 @@ ThreadPool::ThreadPool(ThreadPoolStrategy S) : MaxThreadCount(1) {
 void ThreadPool::wait() {
   // Sequential implementation running the tasks
   while (!Tasks.empty()) {
-    auto Task = std::move(Tasks.front());
-    Tasks.pop();
+    auto Task = std::move(Tasks.front().first);
+    Tasks.pop_front();
     Task();
   }
 }
 
+void ThreadPool::wait(ThreadPoolTaskGroup &) {
+  // Simply wait for all, this works even if recursive (the running task
+  // is already removed from the queue).
+  wait();
+}
+
 bool ThreadPool::isWorkerThread() const {
   report_fatal_error("LLVM compiled without multithreading");
 }