path: root/include/lldb/Host/Mutex.h

//===-- Mutex.h -------------------------------------------------*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#ifndef liblldb_Mutex_h_
#define liblldb_Mutex_h_

// C Includes
// C++ Includes
#ifdef LLDB_CONFIGURATION_DEBUG
#include <string>
#endif

// Other libraries and framework includes
// Project includes
#include "lldb/lldb-types.h"

namespace lldb_private {

//----------------------------------------------------------------------
/// @class Mutex Mutex.h "lldb/Host/Mutex.h"
/// @brief A C++ wrapper class for pthread mutexes.
//----------------------------------------------------------------------
class Mutex
{
public:
    friend class Locker;
    friend class Condition;
    
    enum Type
    {
        eMutexTypeNormal,       ///< Mutex that can't recursively entered by the same thread
        eMutexTypeRecursive     ///< Mutex can be recursively entered by the same thread
    };

    //------------------------------------------------------------------
    /// @class Mutex::Locker
    ///
    /// A scoped locking class that allows a variety of pthread mutex
    /// objects to have a mutex locked when an Mutex::Locker
    /// object is created, and unlocked when it goes out of scope or
    /// when the Mutex::Locker::Reset(pthread_mutex_t *)
    /// is called. This provides an exception safe way to lock a mutex
    /// in a scope.
    //------------------------------------------------------------------
    class Locker
    {
    public:
        //--------------------------------------------------------------
        /// Default constructor.
        ///
        /// This will create a scoped mutex locking object that doesn't
        /// have a mutex to lock. One will need to be provided using the
        /// Mutex::Locker::Reset(pthread_mutex_t *) method.
        ///
        /// @see Mutex::Locker::Reset(pthread_mutex_t *)
        //--------------------------------------------------------------
        Locker();

        //--------------------------------------------------------------
        /// Constructor with a Mutex object.
        ///
        /// This will create a scoped mutex locking object that extracts
        /// the mutex owned by \a m and locks it.
        ///
        /// @param[in] m
        ///     An instance of a Mutex object that contains a
        ///     valid mutex object.
        //--------------------------------------------------------------
        Locker(Mutex& m);

        //--------------------------------------------------------------
        /// Constructor with a Mutex object pointer.
        ///
        /// This will create a scoped mutex locking object that extracts
        /// the mutex owned by a m and locks it.
        ///
        /// @param[in] m
        ///     A pointer to instance of a Mutex object that
        ///     contains a valid mutex object.
        //--------------------------------------------------------------
        Locker(Mutex* m);

        //--------------------------------------------------------------
        /// Destructor
        ///
        /// Unlocks any valid pthread_mutex_t that this object may
        /// contain.
        //--------------------------------------------------------------
        ~Locker();

        //--------------------------------------------------------------
        /// Change the contained mutex.
        ///
        /// Unlock the current mutex in this object (if it contains a
        /// valid mutex) and lock the new \a mutex object if it is
        /// non-nullptr.
        //--------------------------------------------------------------
        void
        Lock (Mutex &mutex);
        
        void
        Lock (Mutex *mutex)
        {
            if (mutex)
                Lock(*mutex);
        }

        //--------------------------------------------------------------
        /// Change the contained mutex only if the mutex can be locked.
        ///
        /// Unlock the current mutex in this object (if it contains a
        /// valid mutex) and try to lock \a mutex. If \a mutex can be 
        /// locked this object will take ownership of the lock and will
        /// unlock it when it goes out of scope or Reset or TryLock are
        /// called again. If the mutex is already locked, this object
        /// will not take ownership of the mutex.
        ///
        /// @return
        ///     Returns \b true if the lock was acquired and the this
        ///     object will unlock the mutex when it goes out of scope,
        ///     returns \b false otherwise.
        //--------------------------------------------------------------
        bool
        TryLock(Mutex &mutex, const char *failure_message = nullptr);
        
        bool
        TryLock(Mutex *mutex, const char *failure_message = nullptr)
        {
            if (mutex)
                return TryLock(*mutex, failure_message);
            else
                return false;
        }

        void
        Unlock ();

    protected:
        //--------------------------------------------------------------
        /// Member variables
        //--------------------------------------------------------------
        Mutex *m_mutex_ptr;

    private:
        Locker(const Locker&);
        const Locker& operator=(const Locker&);
    };

    //------------------------------------------------------------------
    /// Default constructor.
    ///
    /// Creates a pthread mutex with no attributes.
    //------------------------------------------------------------------
    Mutex();

    //------------------------------------------------------------------
    /// Default constructor.
    ///
    /// Creates a pthread mutex with \a type as the mutex type.
    /// Valid values for \a type include:
    ///     @li Mutex::Type::eMutexTypeNormal
    ///     @li Mutex::Type::eMutexTypeRecursive
    ///
    /// @param[in] type
    ///     The type of the mutex.
    ///
    /// @see ::pthread_mutexattr_settype()
    //------------------------------------------------------------------
    Mutex(Mutex::Type type);

    //------------------------------------------------------------------
    /// Destructor.
    ///
    /// Destroys the mutex owned by this object.
    //------------------------------------------------------------------
#ifdef LLDB_CONFIGURATION_DEBUG
    virtual
#endif
    ~Mutex();

    //------------------------------------------------------------------
    /// Lock the mutex.
    ///
    /// Locks the mutex owned by this object. If the mutex is already
    /// locked, the calling thread will block until the mutex becomes
    /// available.
    ///
    /// @return
    ///     The error code from \c pthread_mutex_lock().
    //------------------------------------------------------------------
#ifdef LLDB_CONFIGURATION_DEBUG
    virtual
#endif
    int
    Lock();

    //------------------------------------------------------------------
    /// Try to lock the mutex.
    ///
    /// Attempts to lock the mutex owned by this object without blocking.
    /// If the mutex is already locked, TryLock() will not block waiting
    /// for the mutex, but will return an error condition.
    ///
    /// @return
    ///     The error code from \c pthread_mutex_trylock().
    //------------------------------------------------------------------
#ifdef LLDB_CONFIGURATION_DEBUG
    virtual
#endif
    int
    TryLock(const char *failure_message = nullptr);

    //------------------------------------------------------------------
    /// Unlock the mutex.
    ///
    /// If the current thread holds the lock on the owned mutex, then
    /// Unlock() will unlock the mutex. Calling Unlock() on this object
    /// when the calling thread does not hold the lock will result in
    /// undefined behavior.
    ///
    /// @return
    ///     The error code from \c pthread_mutex_unlock().
    //------------------------------------------------------------------
#ifdef LLDB_CONFIGURATION_DEBUG
    virtual
#endif
    int
    Unlock();

protected:
    //------------------------------------------------------------------
    // Member variables
    //------------------------------------------------------------------
    // TODO: Hide the mutex in the implementation file in case we ever need to port to an
    // architecture that doesn't have pthread mutexes.
    lldb::mutex_t m_mutex; ///< The OS mutex object.

private:
    //------------------------------------------------------------------
    /// Mutex get accessor.
    ///
    /// @return
    ///     A pointer to the pthread mutex object owned by this object.
    //------------------------------------------------------------------
    lldb::mutex_t *
    GetMutex();

    Mutex(const Mutex&);
    const Mutex& operator=(const Mutex&);
};

#ifdef LLDB_CONFIGURATION_DEBUG
class TrackingMutex : public Mutex
{
public:
    TrackingMutex() : Mutex()  {}
    TrackingMutex(Mutex::Type type) : Mutex (type) {}
    
    virtual
    ~TrackingMutex() = default;
    
    virtual int
    Unlock ();

    virtual int
    TryLock(const char *failure_message = nullptr)
    {
        int return_value = Mutex::TryLock();
        if (return_value != 0 && failure_message != nullptr)
        {
            m_failure_message.assign(failure_message);
            m_thread_that_tried = pthread_self();
        }
        return return_value;
    }
    
protected:
    pthread_t m_thread_that_tried;
    std::string m_failure_message;
};

class LoggingMutex : public Mutex
{
public:
    LoggingMutex() : Mutex(),m_locked(false)  {}
    LoggingMutex(Mutex::Type type) : Mutex (type),m_locked(false) {}
    
    virtual
    ~LoggingMutex() = default;
    
    virtual int
    Lock ();
    
    virtual int
    Unlock ();
    
    virtual int
    TryLock(const char *failure_message = nullptr);

protected:
    bool m_locked;
};
#endif // LLDB_CONFIGURATION_DEBUG

} // namespace lldb_private

#endif // liblldb_Mutex_h_