/*
* Copyright 2016-2018, Intel Corporation
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* * 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.
*
* * Neither the name of the copyright holder nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* 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.
*/
/**
* @file
* Pmem-resident shared mutex.
*/
#ifndef LIBPMEMOBJ_CPP_SHARED_MUTEX_HPP
#define LIBPMEMOBJ_CPP_SHARED_MUTEX_HPP
#include <libpmemobj/thread.h>
#include <libpmemobj/tx_base.h>
namespace pmem
{
namespace obj
{
/**
* Persistent memory resident shared_mutex implementation.
*
* This class is an implementation of a PMEM-resident share_mutex
* which mimics in behavior the C++11 std::mutex. This class
* satisfies all requirements of the SharedMutex and StandardLayoutType
* concepts. The typical usage would be:
* @snippet doc_snippets/mutex.cpp shared_mutex_example
*/
class shared_mutex {
public:
/** Implementation defined handle to the native type. */
typedef PMEMrwlock *native_handle_type;
/**
* Default constructor.
*
* @throw lock_error when the shared_mutex is not from persistent
* memory.
*/
shared_mutex()
{
PMEMobjpool *pop;
if ((pop = pmemobj_pool_by_ptr(&plock)) == nullptr)
throw lock_error(
1, std::generic_category(),
"Persistent shared mutex not from persistent memory.");
pmemobj_rwlock_zero(pop, &plock);
}
/**
* Defaulted destructor.
*/
~shared_mutex() = default;
/**
* Lock the mutex for exclusive access.
*
* If a different thread already locked this mutex, the calling
* thread will block. If the same thread tries to lock a mutex
* it already owns, either in exclusive or shared mode,
* the behavior is undefined.
*
* @throw lock_error when an error occurs, this includes all
* system related errors with the underlying implementation of
* the mutex.
*/
void
lock()
{
PMEMobjpool *pop = pmemobj_pool_by_ptr(this);
if (int ret = pmemobj_rwlock_wrlock(pop, &this->plock))
throw lock_error(ret, std::system_category(),
"Failed to lock a shared mutex.");
}
/**
* Lock the mutex for shared access.
*
* If a different thread already locked this mutex for exclusive
* access, the calling thread will block. If it was locked for
* shared access by a different thread, the lock will succeed.
*
* The mutex can be locked for shared access multiple times
* by the same thread. If so, the same number of unlocks must be
* made to unlock the mutex.
*
* @throw lock_error when an error occurs, this includes all
* system related errors with the underlying implementation of
* the mutex.
*/
void
lock_shared()
{
PMEMobjpool *pop = pmemobj_pool_by_ptr(this);
if (int ret = pmemobj_rwlock_rdlock(pop, &this->plock))
throw lock_error(
ret, std::system_category(),
"Failed to shared lock a shared mutex.");
}
/**
* Try to lock the mutex for exclusive access, returns
* regardless if the lock succeeds.
*
* If the same thread tries to lock a mutex it already owns
* either in exclusive or shared mode, the behavior is undefined.
*
* @return `true` on successful lock acquisition, `false`
* otherwise.
*
* @throw lock_error when an error occurs, this includes all
* system related errors with the underlying implementation of
* the mutex.
*/
bool
try_lock()
{
PMEMobjpool *pop = pmemobj_pool_by_ptr(this);
int ret = pmemobj_rwlock_trywrlock(pop, &this->plock);
if (ret == 0)
return true;
else if (ret == EBUSY)
return false;
else
throw lock_error(ret, std::system_category(),
"Failed to lock a shared mutex.");
}
/**
* Try to lock the mutex for shared access, returns
* regardless if the lock succeeds.
*
* The mutex can be locked for shared access multiple times
* by the same thread. If so, the same number of unlocks must be
* made to unlock the mutex. If the calling thread already owns
* the mutex in any mode, the behavior is undefined.
*
* @return `false` if a different thread already locked the
* mutex for exclusive access, `true` otherwise.
*
* @throw lock_error when an error occurs, this includes all
* system related errors with the underlying implementation of
* the mutex.
*/
bool
try_lock_shared()
{
PMEMobjpool *pop = pmemobj_pool_by_ptr(this);
int ret = pmemobj_rwlock_tryrdlock(pop, &this->plock);
if (ret == 0)
return true;
else if (ret == EBUSY)
return false;
else
throw lock_error(ret, std::system_category(),
"Failed to lock a shared mutex.");
}
/**
* Unlocks the mutex.
*
* The mutex must be locked for exclusive access by the calling
* thread, otherwise results in undefined behavior.
*/
void
unlock()
{
PMEMobjpool *pop = pmemobj_pool_by_ptr(this);
int ret = pmemobj_rwlock_unlock(pop, &this->plock);
if (ret)
throw lock_error(ret, std::system_category(),
"Failed to unlock a shared mutex.");
}
/**
* Unlocks the mutex.
*
* The mutex must be locked for shared access by the calling
* thread, otherwise results in undefined behavior.
*/
void
unlock_shared()
{
this->unlock();
}
/**
* Access a native handle to this shared mutex.
*
* @return a pointer to PMEMmutex.
*/
native_handle_type
native_handle() noexcept
{
return &this->plock;
}
/**
* The type of lock needed for the transaction API.
*
* @return TX_PARAM_RWLOCK
*/
enum pobj_tx_param
lock_type() const noexcept
{
return TX_PARAM_RWLOCK;
}
/**
* Deleted assignment operator.
*/
shared_mutex &operator=(const shared_mutex &) = delete;
/**
* Deleted copy constructor.
*/
shared_mutex(const shared_mutex &) = delete;
private:
/** A POSIX style PMEM-resident shared_mutex.*/
PMEMrwlock plock;
};
} /* namespace obj */
} /* namespace pmem */
#endif /* LIBPMEMOBJ_CPP_SHARED_MUTEX_HPP */