c++/src/kj/mutex-test.c++

// Copyright (c) 2013, Kenton Varda <temporal@gmail.com>
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
// 1. Redistributions of source code must retain the above copyright notice, this
//    list of conditions and the following disclaimer.
// 2. Redistributions in binary form must reproduce the above copyright notice,
//    this list of conditions and the following disclaimer in the documentation
//    and/or other materials provided with the distribution.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
// ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
// WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
// ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
// (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
// LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
// ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
// SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

#include "mutex.h"
#include "debug.h"
#include "thread.h"
#include <pthread.h>
#include <unistd.h>
#include <gtest/gtest.h>

namespace kj {
namespace {

inline void delay() { usleep(10000); }

#if KJ_NO_EXCEPTIONS
#undef EXPECT_ANY_THROW
#define EXPECT_ANY_THROW(code) EXPECT_DEATH(code, ".")
#define EXPECT_NONFATAL_FAILURE(code) code
#else
#define EXPECT_NONFATAL_FAILURE EXPECT_ANY_THROW
#endif

#ifdef KJ_DEBUG
#define EXPECT_DEBUG_ANY_THROW EXPECT_ANY_THROW
#else
#define EXPECT_DEBUG_ANY_THROW(EXP)
#endif

TEST(Mutex, MutexGuarded) {
  MutexGuarded<uint> value(123);

  {
    Locked<uint> lock = value.lockExclusive();
    EXPECT_EQ(123u, *lock);
    EXPECT_EQ(123u, value.getAlreadyLockedExclusive());

    Thread thread([&]() {
      Locked<uint> threadLock = value.lockExclusive();
      EXPECT_EQ(456u, *threadLock);
      *threadLock = 789;
    });

    delay();
    EXPECT_EQ(123u, *lock);
    *lock = 456;
    auto earlyRelease = kj::mv(lock);
  }

  EXPECT_EQ(789u, *value.lockExclusive());

  {
    auto rlock1 = value.lockShared();
    EXPECT_EQ(789u, *rlock1);
    EXPECT_EQ(789u, value.getAlreadyLockedShared());

    {
      auto rlock2 = value.lockShared();
      EXPECT_EQ(789u, *rlock2);
      auto rlock3 = value.lockShared();
      EXPECT_EQ(789u, *rlock3);
      auto rlock4 = value.lockShared();
      EXPECT_EQ(789u, *rlock4);
    }

    Thread thread2([&]() {
      Locked<uint> threadLock = value.lockExclusive();
      *threadLock = 321;
    });

#if KJ_USE_FUTEX
    // So, it turns out that pthread_rwlock on BSD "prioritizes" readers over writers.  The result
    // is that if one thread tries to take multiple read locks, but another thread happens to
    // request a write lock it between, you get a deadlock.  This seems to contradict the man pages
    // and common sense, but this is how it is.  The futex-based implementation doesn't currently
    // have this problem because it does not prioritize writers.  Perhaps it will in the future,
    // but we'll leave this test here until then to make sure we notice the change.

    delay();
    EXPECT_EQ(789u, *rlock1);

    {
      auto rlock2 = value.lockShared();
      EXPECT_EQ(789u, *rlock2);
      auto rlock3 = value.lockShared();
      EXPECT_EQ(789u, *rlock3);
      auto rlock4 = value.lockShared();
      EXPECT_EQ(789u, *rlock4);
    }
#endif

    delay();
    EXPECT_EQ(789u, *rlock1);
    auto earlyRelease = kj::mv(rlock1);
  }

  EXPECT_EQ(321u, *value.lockExclusive());

  EXPECT_DEBUG_ANY_THROW(value.getAlreadyLockedExclusive());
  EXPECT_DEBUG_ANY_THROW(value.getAlreadyLockedShared());
  EXPECT_EQ(321u, value.getWithoutLock());
}

TEST(Mutex, Lazy) {
  Lazy<uint> lazy;
  bool initStarted = false;

  Thread thread([&]() {
    EXPECT_EQ(123u, lazy.get([&](SpaceFor<uint>& space) -> Own<uint> {
      __atomic_store_n(&initStarted, true, __ATOMIC_RELAXED);
      delay();
      return space.construct(123);
    }));
  });

  // Spin until the initializer has been entered in the thread.
  while (!__atomic_load_n(&initStarted, __ATOMIC_RELAXED)) {
    sched_yield();
  }

  EXPECT_EQ(123u, lazy.get([](SpaceFor<uint>& space) { return space.construct(456); }));
  EXPECT_EQ(123u, lazy.get([](SpaceFor<uint>& space) { return space.construct(789); }));
}

}  // namespace
}  // namespace kj