text: //===----------------------------------------------------------------------===//
  //
  // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
  // See https://llvm.org/LICENSE.txt for license information.
  // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
  //
  //===----------------------------------------------------------------------===//
  //
  // UNSUPPORTED: libcpp-has-no-threads
  // UNSUPPORTED: c++03, c++11
  
  // dylib support for shared_mutex was added in macosx10.12
  // XFAIL: use_system_cxx_lib && target={{.+}}-apple-macosx10.{{9|10|11}}
  
  // TODO(ldionne): This test fails on Ubuntu Focal on our CI nodes (and only there), in 32 bit mode.
  // UNSUPPORTED: linux && 32bits-on-64bits
  
  // <shared_mutex>
  
  // class shared_timed_mutex;
  
  // template <class Clock, class Duration>
  //   shared_lock(mutex_type& m, const chrono::time_point<Clock, Duration>& abs_time);
  
  #include <thread>
  
  #include <atomic>
  #include <cassert>
  #include <cstdlib>
  #include <shared_mutex>
  #include <vector>
  
  #include "make_test_thread.h"
  #include "test_macros.h"
  
  std::shared_timed_mutex m;
  
  typedef std::chrono::steady_clock Clock;
  typedef Clock::time_point time_point;
  typedef Clock::duration duration;
  typedef std::chrono::milliseconds ms;
  typedef std::chrono::nanoseconds ns;
  
  ms LongTime = ms(5000);
  ms ShortTime = ms(50);
  
  static constexpr unsigned Threads = 5;
  
  std::atomic<unsigned> CountDown(Threads);
  
  void f1()
  {
    --CountDown;
    time_point t0 = Clock::now();
    std::shared_lock<std::shared_timed_mutex> lk(m, t0 + LongTime);
    time_point t1 = Clock::now();
    assert(lk.owns_lock() == true);
    assert(t1 - t0 <= LongTime);
  }
  
  void f2()
  {
    time_point t0 = Clock::now();
    std::shared_lock<std::shared_timed_mutex> lk(m, t0 + ShortTime);
    time_point t1 = Clock::now();
    assert(lk.owns_lock() == false);
    assert(t1 - t0 >= ShortTime);
  }
  
  int main(int, char**)
  {
    {
      m.lock();
      std::vector<std::thread> v;
      for (unsigned i = 0; i < Threads; ++i)
        v.push_back(support::make_test_thread(f1));
      while (CountDown > 0)
        std::this_thread::yield();
      std::this_thread::sleep_for(ShortTime);
      m.unlock();
      for (auto& t : v)
        t.join();
    }
    {
      m.lock();
      std::vector<std::thread> v;
      for (unsigned i = 0; i < Threads; ++i)
        v.push_back(support::make_test_thread(f2));
      for (auto& t : v)
        t.join();
      m.unlock();
    }
  
    return 0;
  }
  