clang-tools  12.0.0git
BackgroundQueue.cpp
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1 //===-- BackgroundQueue.cpp - Task queue for background index -------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
9 #include "index/Background.h"
10 #include "support/Logger.h"
11 
12 namespace clang {
13 namespace clangd {
14 
15 static std::atomic<bool> PreventStarvation = {false};
16 
18  PreventStarvation.store(true);
19 }
20 
21 void BackgroundQueue::work(std::function<void()> OnIdle) {
22  while (true) {
23  llvm::Optional<Task> Task;
24  {
25  std::unique_lock<std::mutex> Lock(Mu);
26  CV.wait(Lock, [&] { return ShouldStop || !Queue.empty(); });
27  if (ShouldStop) {
28  Queue.clear();
29  CV.notify_all();
30  return;
31  }
32  ++Stat.Active;
33  std::pop_heap(Queue.begin(), Queue.end());
34  Task = std::move(Queue.back());
35  Queue.pop_back();
36  notifyProgress();
37  }
38 
39  if (Task->ThreadPri != llvm::ThreadPriority::Default &&
40  !PreventStarvation.load())
41  llvm::set_thread_priority(Task->ThreadPri);
42  Task->Run();
43  if (Task->ThreadPri != llvm::ThreadPriority::Default)
44  llvm::set_thread_priority(llvm::ThreadPriority::Default);
45 
46  {
47  std::unique_lock<std::mutex> Lock(Mu);
48  ++Stat.Completed;
49  if (Stat.Active == 1 && Queue.empty()) {
50  // We just finished the last item, the queue is going idle.
51  assert(ShouldStop || Stat.Completed == Stat.Enqueued);
52  Stat.LastIdle = Stat.Completed;
53  if (OnIdle) {
54  Lock.unlock();
55  OnIdle();
56  Lock.lock();
57  }
58  }
59  assert(Stat.Active > 0 && "before decrementing");
60  --Stat.Active;
61  notifyProgress();
62  }
63  CV.notify_all();
64  }
65 }
66 
68  {
69  std::lock_guard<std::mutex> QueueLock(Mu);
70  ShouldStop = true;
71  }
72  CV.notify_all();
73 }
74 
76  {
77  std::lock_guard<std::mutex> Lock(Mu);
78  T.QueuePri = std::max(T.QueuePri, Boosts.lookup(T.Tag));
79  Queue.push_back(std::move(T));
80  std::push_heap(Queue.begin(), Queue.end());
81  ++Stat.Enqueued;
82  notifyProgress();
83  }
84  CV.notify_all();
85 }
86 
87 void BackgroundQueue::append(std::vector<Task> Tasks) {
88  {
89  std::lock_guard<std::mutex> Lock(Mu);
90  for (Task &T : Tasks)
91  T.QueuePri = std::max(T.QueuePri, Boosts.lookup(T.Tag));
92  std::move(Tasks.begin(), Tasks.end(), std::back_inserter(Queue));
93  std::make_heap(Queue.begin(), Queue.end());
94  Stat.Enqueued += Tasks.size();
95  notifyProgress();
96  }
97  CV.notify_all();
98 }
99 
100 void BackgroundQueue::boost(llvm::StringRef Tag, unsigned NewPriority) {
101  std::lock_guard<std::mutex> Lock(Mu);
102  unsigned &Boost = Boosts[Tag];
103  bool Increase = NewPriority > Boost;
104  Boost = NewPriority;
105  if (!Increase)
106  return; // existing tasks unaffected
107 
108  unsigned Changes = 0;
109  for (Task &T : Queue)
110  if (Tag == T.Tag && NewPriority > T.QueuePri) {
111  T.QueuePri = NewPriority;
112  ++Changes;
113  }
114  if (Changes)
115  std::make_heap(Queue.begin(), Queue.end());
116  // No need to signal, only rearranged items in the queue.
117 }
118 
120  llvm::Optional<double> TimeoutSeconds) {
121  std::unique_lock<std::mutex> Lock(Mu);
122  return wait(Lock, CV, timeoutSeconds(TimeoutSeconds),
123  [&] { return Queue.empty() && Stat.Active == 0; });
124 }
125 
126 void BackgroundQueue::notifyProgress() const {
127  dlog("Queue: {0}/{1} ({2} active). Last idle at {3}", Stat.Completed,
128  Stat.Enqueued, Stat.Active, Stat.LastIdle);
129  if (OnProgress)
130  OnProgress(Stat);
131 }
132 
133 } // namespace clangd
134 } // namespace clang
static std::atomic< bool > PreventStarvation
tooling::Replacements Changes
Definition: Format.cpp:109
HTMLTag Tag
void boost(llvm::StringRef Tag, unsigned NewPriority)
static void preventThreadStarvationInTests()
#define dlog(...)
Definition: Logger.h:72
void wait(std::unique_lock< std::mutex > &Lock, std::condition_variable &CV, Deadline D)
Wait once on CV for the specified duration.
Definition: Threading.cpp:110
LLVM_NODISCARD bool blockUntilIdleForTest(llvm::Optional< double > TimeoutSeconds)
===– Representation.cpp - ClangDoc Representation --------—*- C++ -*-===//
Deadline timeoutSeconds(llvm::Optional< double > Seconds)
Makes a deadline from a timeout in seconds. None means wait forever.
Definition: Threading.cpp:102
void append(std::vector< Task >)
A work item on the thread pool&#39;s queue.
Definition: Background.h:70
void work(std::function< void()> OnIdle=nullptr)