libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.sharedtimedmutex.requirements/thread.sharedtimedmutex.class/try_lock_shared.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
  11
  12 // ALLOW_RETRIES: 2
  13
  14 // <shared_mutex>
  15
  16 // class shared_timed_mutex;
  17
  18 // bool try_lock_shared();
  19
  20 #include <cassert>
  21 #include <chrono>
  22 #include <cstdlib>
  23 #include <shared_mutex>
  24 #include <thread>
  25 #include <vector>
  26
  27 #include "make_test_thread.h"
  28 #include "test_macros.h"
  29
  30 std::shared_timed_mutex m;
  31
  32 typedef std::chrono::system_clock Clock;
  33 typedef Clock::time_point time_point;
  34 typedef Clock::duration duration;
  35 typedef std::chrono::milliseconds ms;
  36 typedef std::chrono::nanoseconds ns;
  37
  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(200);
  44 #else
  45 ms Tolerance = ms(200 * 5);
  46 #endif
  47
  48 void f()
  49 {
  50     time_point t0 = Clock::now();
  51     assert(!m.try_lock_shared());
  52     assert(!m.try_lock_shared());
  53     assert(!m.try_lock_shared());
  54     while(!m.try_lock_shared())
  55         std::this_thread::yield();
  56     time_point t1 = Clock::now();
  57     m.unlock_shared();
  58     ns d = t1 - t0 - ms(250);
  59     assert(d < Tolerance);  // within tolerance
  60 }
  61
  62 int main(int, char**)
  63 {
  64     m.lock();
  65     std::vector<std::thread> v;
  66     for (int i = 0; i < 5; ++i)
  67         v.push_back(support::make_test_thread(f));
  68     std::this_thread::sleep_for(ms(250));
  69     m.unlock();
  70     for (auto& t : v)
  71         t.join();
  72
  73   return 0;
  74 }