[PATCH] D55359: [clangd] Avoid emitting Queued status when we are able to acquire the Barrier.

[Haojian Wu via Phabricator via cfe-commits]

hokein created this revision.
hokein added a reviewer: ilya-biryukov.
Herald added subscribers: kadircet, arphaman, jkorous, MaskRay, ioeric, javed.absar.

Repository:
  rCTE Clang Tools Extra

https://reviews.llvm.org/D55359

Files:
  clangd/TUScheduler.cpp
  clangd/Threading.cpp
  clangd/Threading.h
  unittests/clangd/TUSchedulerTests.cpp


Index: unittests/clangd/TUSchedulerTests.cpp
===================================================================
--- unittests/clangd/TUSchedulerTests.cpp
+++ unittests/clangd/TUSchedulerTests.cpp
@@ -698,13 +698,11 @@
   EXPECT_THAT(CaptureTUStatus.AllStatus,
               ElementsAre(
                   // Statuses of "Update" action.
-                  TUState(TUAction::Queued, "Update"),
                   TUState(TUAction::RunningAction, "Update"),
                   TUState(TUAction::BuildingPreamble, "Update"),
                   TUState(TUAction::BuildingFile, "Update"),
 
                   // Statuses of "Definitions" action
-                  TUState(TUAction::Queued, "Definitions"),
                   TUState(TUAction::RunningAction, "Definitions"),
                   TUState(TUAction::Idle, /*No action*/ "")));
 }
Index: clangd/Threading.h
===================================================================
--- clangd/Threading.h
+++ clangd/Threading.h
@@ -42,6 +42,7 @@
 public:
   Semaphore(std::size_t MaxLocks);
 
+  bool try_lock();
   void lock();
   void unlock();
 
Index: clangd/Threading.cpp
===================================================================
--- clangd/Threading.cpp
+++ clangd/Threading.cpp
@@ -28,6 +28,15 @@
 
 Semaphore::Semaphore(std::size_t MaxLocks) : FreeSlots(MaxLocks) {}
 
+bool Semaphore::try_lock() {
+  std::unique_lock<std::mutex> Lock(Mutex);
+  if (FreeSlots > 0) {
+    --FreeSlots;
+    return true;
+  }
+  return false;
+}
+
 void Semaphore::lock() {
   trace::Span Span("WaitForFreeSemaphoreSlot");
   // trace::Span can also acquire locks in ctor and dtor, we make sure it
Index: clangd/TUScheduler.cpp
===================================================================
--- clangd/TUScheduler.cpp
+++ clangd/TUScheduler.cpp
@@ -634,13 +634,22 @@
     } // unlock Mutex
 
     {
-      // FIXME: only emit this status when the Barrier couldn't be acquired.
-      emitTUStatus({TUAction::Queued, Req.Name});
-      std::lock_guard<Semaphore> BarrierLock(Barrier);
-      WithContext Guard(std::move(Req.Ctx));
-      trace::Span Tracer(Req.Name);
-      emitTUStatus({TUAction::RunningAction, Req.Name});
-      Req.Action();
+      auto ExecuteAction = [&]() {
+        WithContext Guard(std::move(Req.Ctx));
+        trace::Span Tracer(Req.Name);
+        emitTUStatus({TUAction::RunningAction, Req.Name});
+        Req.Action();
+      };
+      std::unique_lock<Semaphore> Lock(Barrier, std::try_to_lock);
+      if (Lock.owns_lock()) {
+        ExecuteAction();
+      } else {
+        emitTUStatus({TUAction::Queued, Req.Name});
+        {
+          std::lock_guard<Semaphore> BarrierLock(Barrier);
+          ExecuteAction();
+        }
+      }
     }
 
     bool IsEmpty = false;


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