libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.shared_mutex.requirements/thread.shared_mutex.class/lock.pass.cpp

   1 //===----------------------------------------------------------------------===//
   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 // UNSUPPORTED: no-threads
  10 // UNSUPPORTED: c++03, c++11, c++14
  11
  12 // ALLOW_RETRIES: 2
  13
  14 // <shared_mutex>
  15
  16 // class shared_mutex;
  17
  18 // void lock();
  19
  20 #include <cassert>
  21 #include <chrono>
  22 #include <cstdlib>
  23 #include <shared_mutex>
  24 #include <thread>
  25
  26 #include "make_test_thread.h"
  27 #include "test_macros.h"
  28
  29 std::shared_mutex m;
  30
  31 typedef std::chrono::system_clock Clock;
  32 typedef Clock::time_point time_point;
  33 typedef Clock::duration duration;
  34 typedef std::chrono::milliseconds ms;
  35 typedef std::chrono::nanoseconds ns;
  36
  37 ms WaitTime = ms(250);
  38
  39 // Thread sanitizer causes more overhead and will sometimes cause this test
  40 // to fail. To prevent this we give Thread sanitizer more time to complete the
  41 // test.
  42 #if !defined(TEST_IS_EXECUTED_IN_A_SLOW_ENVIRONMENT)
  43 ms Tolerance = ms(50);
  44 #else
  45 ms Tolerance = ms(50 * 5);
  46 #endif
  47
  48 void f()
  49 {
  50     time_point t0 = Clock::now();
  51     m.lock();
  52     time_point t1 = Clock::now();
  53     m.unlock();
  54     ns d = t1 - t0 - WaitTime;
  55     assert(d < Tolerance);  // within tolerance
  56 }
  57
  58 int main(int, char**)
  59 {
  60     m.lock();
  61     std::thread t = support::make_test_thread(f);
  62     std::this_thread::sleep_for(WaitTime);
  63     m.unlock();
  64     t.join();
  65
  66   return 0;
  67 }