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      1 //===----------------------------------------------------------------------===//
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is dual licensed under the MIT and the University of Illinois Open
      6 // Source Licenses. See LICENSE.TXT for details.
      7 //
      8 //===----------------------------------------------------------------------===//
      9 
     10 // <mutex>
     11 
     12 // class recursive_mutex;
     13 
     14 // bool try_lock();
     15 
     16 #include <mutex>
     17 #include <thread>
     18 #include <cstdlib>
     19 #include <cassert>
     20 
     21 std::recursive_mutex m;
     22 
     23 typedef std::chrono::system_clock Clock;
     24 typedef Clock::time_point time_point;
     25 typedef Clock::duration duration;
     26 typedef std::chrono::milliseconds ms;
     27 typedef std::chrono::nanoseconds ns;
     28 
     29 void f()
     30 {
     31     time_point t0 = Clock::now();
     32     assert(!m.try_lock());
     33     assert(!m.try_lock());
     34     assert(!m.try_lock());
     35     while(!m.try_lock())
     36         ;
     37     time_point t1 = Clock::now();
     38     assert(m.try_lock());
     39     m.unlock();
     40     m.unlock();
     41     ns d = t1 - t0 - ms(250);
     42     assert(d < ms(200));  // within 200ms
     43 }
     44 
     45 int main()
     46 {
     47     m.lock();
     48     std::thread t(f);
     49     std::this_thread::sleep_for(ms(250));
     50     m.unlock();
     51     t.join();
     52 }
     53