libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.shared/thread.lock.shared.cons/mutex_duration.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 // <shared_mutex>
  13
  14 // class timed_mutex;
  15
  16 // template <class Rep, class Period>
  17 //   shared_lock(mutex_type& m, const chrono::duration<Rep, Period>& rel_time);
  18
  19 #include <thread>
  20
  21 #include <atomic>
  22 #include <cassert>
  23 #include <chrono>
  24 #include <cstdlib>
  25 #include <shared_mutex>
  26 #include <vector>
  27
  28 #include "make_test_thread.h"
  29 #include "test_macros.h"
  30
  31 std::shared_timed_mutex m;
  32
  33 typedef std::chrono::steady_clock Clock;
  34 typedef Clock::time_point time_point;
  35 typedef Clock::duration duration;
  36 typedef std::chrono::milliseconds ms;
  37 typedef std::chrono::nanoseconds ns;
  38
  39 ms LongTime = ms(5000);
  40 ms ShortTime = ms(50);
  41
  42 static const unsigned Threads = 5;
  43
  44 std::atomic<unsigned> CountDown(Threads);
  45
  46 void f1()
  47 {
  48   // Preemptive scheduling means that one cannot make assumptions about when
  49   // code executes and therefore we cannot assume anything about when the mutex
  50   // starts waiting relative to code in the main thread. We can however prove
  51   // that a timeout occurred and that implies that this code is waiting.
  52   // See f2() below.
  53   //
  54   // Nevertheless, we should at least try to ensure that the mutex waits and
  55   // therefore we use an atomic variable to signal to the main thread that this
  56   // code is just a few instructions away from waiting.
  57   --CountDown;
  58   std::shared_lock<std::shared_timed_mutex> lk(m, LongTime);
  59   assert(lk.owns_lock() == true);
  60 }
  61
  62 void f2()
  63 {
  64   time_point t0 = Clock::now();
  65   std::shared_lock<std::shared_timed_mutex> lk(m, ShortTime);
  66   time_point t1 = Clock::now();
  67   assert(lk.owns_lock() == false);
  68   assert(t1 - t0 >= ShortTime);
  69 }
  70
  71 int main(int, char**)
  72 {
  73   {
  74     m.lock();
  75     std::vector<std::thread> v;
  76     for (unsigned i = 0; i < Threads; ++i)
  77       v.push_back(support::make_test_thread(f1));
  78     while (CountDown > 0)
  79       std::this_thread::yield();
  80     // Give one more chance for threads to block and wait for the mutex.
  81     std::this_thread::yield();
  82     std::this_thread::sleep_for(ShortTime);
  83     m.unlock();
  84     for (auto& t : v)
  85       t.join();
  86   }
  87   {
  88     m.lock();
  89     std::vector<std::thread> v;
  90     for (unsigned i = 0; i < Threads; ++i)
  91       v.push_back(support::make_test_thread(f2));
  92     for (auto& t : v)
  93       t.join();
  94     m.unlock();
  95   }
  96
  97   return 0;
  98 }