1 #include "support/Threading.h"
2 #include "support/Trace.h"
3 #include "llvm/ADT/ScopeExit.h"
4 #include "llvm/Support/FormatVariadic.h"
5 #include "llvm/Support/Threading.h"
6 #include <atomic>
7 #include <thread>
8 #ifdef __USE_POSIX
9 #include <pthread.h>
10 #elif defined(__APPLE__)
11 #include <sys/resource.h>
12 #elif defined(_WIN32)
13 #include <windows.h>
14 #endif
15
16 namespace clang {
17 namespace clangd {
18
notify()19 void Notification::notify() {
20 {
21 std::lock_guard<std::mutex> Lock(Mu);
22 Notified = true;
23 // Broadcast with the lock held. This ensures that it's safe to destroy
24 // a Notification after wait() returns, even from another thread.
25 CV.notify_all();
26 }
27 }
28
wait() const29 void Notification::wait() const {
30 std::unique_lock<std::mutex> Lock(Mu);
31 CV.wait(Lock, [this] { return Notified; });
32 }
33
Semaphore(std::size_t MaxLocks)34 Semaphore::Semaphore(std::size_t MaxLocks) : FreeSlots(MaxLocks) {}
35
try_lock()36 bool Semaphore::try_lock() {
37 std::unique_lock<std::mutex> Lock(Mutex);
38 if (FreeSlots > 0) {
39 --FreeSlots;
40 return true;
41 }
42 return false;
43 }
44
lock()45 void Semaphore::lock() {
46 trace::Span Span("WaitForFreeSemaphoreSlot");
47 // trace::Span can also acquire locks in ctor and dtor, we make sure it
48 // happens when Semaphore's own lock is not held.
49 {
50 std::unique_lock<std::mutex> Lock(Mutex);
51 SlotsChanged.wait(Lock, [&]() { return FreeSlots > 0; });
52 --FreeSlots;
53 }
54 }
55
unlock()56 void Semaphore::unlock() {
57 std::unique_lock<std::mutex> Lock(Mutex);
58 ++FreeSlots;
59 Lock.unlock();
60
61 SlotsChanged.notify_one();
62 }
63
~AsyncTaskRunner()64 AsyncTaskRunner::~AsyncTaskRunner() { wait(); }
65
wait(Deadline D) const66 bool AsyncTaskRunner::wait(Deadline D) const {
67 std::unique_lock<std::mutex> Lock(Mutex);
68 return clangd::wait(Lock, TasksReachedZero, D,
69 [&] { return InFlightTasks == 0; });
70 }
71
runAsync(const llvm::Twine & Name,llvm::unique_function<void ()> Action)72 void AsyncTaskRunner::runAsync(const llvm::Twine &Name,
73 llvm::unique_function<void()> Action) {
74 {
75 std::lock_guard<std::mutex> Lock(Mutex);
76 ++InFlightTasks;
77 }
78
79 auto CleanupTask = llvm::make_scope_exit([this]() {
80 std::lock_guard<std::mutex> Lock(Mutex);
81 int NewTasksCnt = --InFlightTasks;
82 if (NewTasksCnt == 0) {
83 // Note: we can't unlock here because we don't want the object to be
84 // destroyed before we notify.
85 TasksReachedZero.notify_one();
86 }
87 });
88
89 auto Task = [Name = Name.str(), Action = std::move(Action),
90 Cleanup = std::move(CleanupTask)]() mutable {
91 llvm::set_thread_name(Name);
92 Action();
93 // Make sure function stored by ThreadFunc is destroyed before Cleanup runs.
94 Action = nullptr;
95 };
96
97 // Ensure our worker threads have big enough stacks to run clang.
98 llvm::llvm_execute_on_thread_async(std::move(Task),
99 /*clang::DesiredStackSize*/ 8 << 20);
100 }
101
timeoutSeconds(llvm::Optional<double> Seconds)102 Deadline timeoutSeconds(llvm::Optional<double> Seconds) {
103 using namespace std::chrono;
104 if (!Seconds)
105 return Deadline::infinity();
106 return steady_clock::now() +
107 duration_cast<steady_clock::duration>(duration<double>(*Seconds));
108 }
109
wait(std::unique_lock<std::mutex> & Lock,std::condition_variable & CV,Deadline D)110 void wait(std::unique_lock<std::mutex> &Lock, std::condition_variable &CV,
111 Deadline D) {
112 if (D == Deadline::zero())
113 return;
114 if (D == Deadline::infinity())
115 return CV.wait(Lock);
116 CV.wait_until(Lock, D.time());
117 }
118
operator ()()119 bool PeriodicThrottler::operator()() {
120 Rep Now = Stopwatch::now().time_since_epoch().count();
121 Rep OldNext = Next.load(std::memory_order_acquire);
122 if (Now < OldNext)
123 return false;
124 // We're ready to run (but may be racing other threads).
125 // Work out the updated target time, and run if we successfully bump it.
126 Rep NewNext = Now + Period;
127 return Next.compare_exchange_strong(OldNext, NewNext,
128 std::memory_order_acq_rel);
129 }
130
131 } // namespace clangd
132 } // namespace clang
133