sync.h

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// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2016 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
#ifndef BITCOIN_SYNC_H
#define BITCOIN_SYNC_H
 
#ifdef DEBUG_LOCKCONTENTION
#include <logging.h>
#include <logging/timer.h>
#endif
 
#include <threadsafety.h>
#include <util/macros.h>
 
#include <condition_variable>
#include <mutex>
#include <string>
#include <thread>
 
//                                             //
// THE SIMPLE DEFINITION, EXCLUDING DEBUG CODE //
//                                             //
 
/*
RecursiveMutex mutex;
    std::recursive_mutex mutex;
 
LOCK(mutex);
    std::unique_lock<std::recursive_mutex> criticalblock(mutex);
 
LOCK2(mutex1, mutex2);
    std::unique_lock<std::recursive_mutex> criticalblock1(mutex1);
    std::unique_lock<std::recursive_mutex> criticalblock2(mutex2);
 
TRY_LOCK(mutex, name);
    std::unique_lock<std::recursive_mutex> name(mutex, std::try_to_lock_t);
 
ENTER_CRITICAL_SECTION(mutex); // no RAII
    mutex.lock();
 
LEAVE_CRITICAL_SECTION(mutex); // no RAII
    mutex.unlock();
 */
 
//                           //
// THE ACTUAL IMPLEMENTATION //
//                           //
 
#ifdef DEBUG_LOCKORDER
template <typename MutexType>
void EnterCritical(const char *pszName, const char *pszFile, int nLine,
                   MutexType *cs, bool fTry = false);
void LeaveCritical();
void CheckLastCritical(void *cs, std::string &lockname, const char *guardname,
                       const char *file, int line);
std::string LocksHeld();
template <typename MutexType>
void AssertLockHeldInternal(const char *pszName, const char *pszFile, int nLine,
                            MutexType *cs) EXCLUSIVE_LOCKS_REQUIRED(cs);
template <typename MutexType>
void AssertLockNotHeldInternal(const char *pszName, const char *pszFile,
                               int nLine, MutexType *cs) LOCKS_EXCLUDED(cs);
void DeleteLock(void *cs);
bool LockStackEmpty();
 
extern bool g_debug_lockorder_abort;
#else
template <typename MutexType>
inline void EnterCritical(const char *pszName, const char *pszFile, int nLine,
                          MutexType *cs, bool fTry = false) {}
inline void LeaveCritical() {}
inline void CheckLastCritical(void *cs, std::string &lockname,
                              const char *guardname, const char *file,
                              int line) {}
template <typename MutexType>
inline void AssertLockHeldInternal(const char *pszName, const char *pszFile,
                                   int nLine, MutexType *cs)
    EXCLUSIVE_LOCKS_REQUIRED(cs) {}
template <typename MutexType>
void AssertLockNotHeldInternal(const char *pszName, const char *pszFile,
                               int nLine, MutexType *cs) LOCKS_EXCLUDED(cs) {}
inline void DeleteLock(void *cs) {}
inline bool LockStackEmpty() {
    return true;
}
#endif
 
template <typename PARENT> class LOCKABLE AnnotatedMixin : public PARENT {
public:
    ~AnnotatedMixin() { DeleteLock((void *)this); }
 
    void lock() EXCLUSIVE_LOCK_FUNCTION() { PARENT::lock(); }
 
    void unlock() UNLOCK_FUNCTION() { PARENT::unlock(); }
 
    bool try_lock() EXCLUSIVE_TRYLOCK_FUNCTION(true) {
        return PARENT::try_lock();
    }
 
    using UniqueLock = std::unique_lock<PARENT>;
#ifdef __clang__
    const AnnotatedMixin &operator!() const { return *this; }
#endif // __clang__
};
 
using RecursiveMutex = AnnotatedMixin<std::recursive_mutex>;
 
using Mutex = AnnotatedMixin<std::mutex>;
 
class GlobalMutex : public Mutex {};
 
#define AssertLockHeld(cs) AssertLockHeldInternal(#cs, __FILE__, __LINE__, &cs)
 
inline void AssertLockNotHeldInline(const char *name, const char *file,
                                    int line, Mutex *cs)
    EXCLUSIVE_LOCKS_REQUIRED(!cs) {
    AssertLockNotHeldInternal(name, file, line, cs);
}
inline void AssertLockNotHeldInline(const char *name, const char *file,
                                    int line, RecursiveMutex *cs)
    LOCKS_EXCLUDED(cs) {
    AssertLockNotHeldInternal(name, file, line, cs);
}
inline void AssertLockNotHeldInline(const char *name, const char *file,
                                    int line, GlobalMutex *cs)
    LOCKS_EXCLUDED(cs) {
    AssertLockNotHeldInternal(name, file, line, cs);
}
#define AssertLockNotHeld(cs)                                                  \
    AssertLockNotHeldInline(#cs, __FILE__, __LINE__, &cs)
 
template <typename Mutex, typename Base = typename Mutex::UniqueLock>
class SCOPED_LOCKABLE UniqueLock : public Base {
private:
    void Enter(const char *pszName, const char *pszFile, int nLine) {
        EnterCritical(pszName, pszFile, nLine, Base::mutex());
#ifdef DEBUG_LOCKCONTENTION
        if (Base::try_lock()) {
            return;
        }
        LOG_TIME_MICROS_WITH_CATEGORY(
            strprintf("lock contention %s, %s:%d", pszName, pszFile, nLine),
            BCLog::LOCK);
#endif
        Base::lock();
    }
 
    bool TryEnter(const char *pszName, const char *pszFile, int nLine) {
        EnterCritical(pszName, pszFile, nLine, Base::mutex(), true);
        if (Base::try_lock()) {
            return true;
        }
        LeaveCritical();
        return false;
    }
 
public:
    UniqueLock(Mutex &mutexIn, const char *pszName, const char *pszFile,
               int nLine, bool fTry = false) EXCLUSIVE_LOCK_FUNCTION(mutexIn)
        : Base(mutexIn, std::defer_lock) {
        if (fTry) {
            TryEnter(pszName, pszFile, nLine);
        } else {
            Enter(pszName, pszFile, nLine);
        }
    }
 
    UniqueLock(Mutex *pmutexIn, const char *pszName, const char *pszFile,
               int nLine, bool fTry = false) EXCLUSIVE_LOCK_FUNCTION(pmutexIn) {
        if (!pmutexIn) {
            return;
        }
 
        *static_cast<Base *>(this) = Base(*pmutexIn, std::defer_lock);
        if (fTry) {
            TryEnter(pszName, pszFile, nLine);
        } else {
            Enter(pszName, pszFile, nLine);
        }
    }
 
    ~UniqueLock() UNLOCK_FUNCTION() {
        if (Base::owns_lock()) {
            LeaveCritical();
        }
    }
 
    operator bool() { return Base::owns_lock(); }
 
protected:
    // needed for reverse_lock
    UniqueLock() {}
 
public:
    class reverse_lock {
    public:
        explicit reverse_lock(UniqueLock &_lock, const char *_guardname,
                              const char *_file, int _line)
            : lock(_lock), file(_file), line(_line) {
            CheckLastCritical((void *)lock.mutex(), lockname, _guardname, _file,
                              _line);
            lock.unlock();
            LeaveCritical();
            lock.swap(templock);
        }
 
        ~reverse_lock() {
            templock.swap(lock);
            EnterCritical(lockname.c_str(), file.c_str(), line, lock.mutex());
            lock.lock();
        }
 
    private:
        reverse_lock(reverse_lock const &);
        reverse_lock &operator=(reverse_lock const &);
 
        UniqueLock &lock;
        UniqueLock templock;
        std::string lockname;
        const std::string file;
        const int line;
    };
    friend class reverse_lock;
};
 
#define REVERSE_LOCK(g)                                                        \
    typename std::decay<decltype(g)>::type::reverse_lock UNIQUE_LOG_NAME(      \
        revlock)(g, #g, __FILE__, __LINE__)
 
template <typename MutexArg>
using DebugLock = UniqueLock<typename std::remove_reference<
    typename std::remove_pointer<MutexArg>::type>::type>;
 
// When locking a Mutex, require negative capability to ensure the lock
// is not already held
inline Mutex &MaybeCheckNotHeld(Mutex &cs) EXCLUSIVE_LOCKS_REQUIRED(!cs)
    LOCK_RETURNED(cs) {
    return cs;
}
inline Mutex *MaybeCheckNotHeld(Mutex *cs) EXCLUSIVE_LOCKS_REQUIRED(!cs)
    LOCK_RETURNED(cs) {
    return cs;
}
 
// When locking a GlobalMutex, just check it is not locked in the surrounding
// scope
inline GlobalMutex &MaybeCheckNotHeld(GlobalMutex &cs) LOCKS_EXCLUDED(cs)
    LOCK_RETURNED(cs) {
    return cs;
}
inline GlobalMutex *MaybeCheckNotHeld(GlobalMutex *cs) LOCKS_EXCLUDED(cs)
    LOCK_RETURNED(cs) {
    return cs;
}
 
// When locking a RecursiveMutex, it's okay to already hold the lock
// but check that it is not known to be locked in the surrounding scope anyway
inline RecursiveMutex &MaybeCheckNotHeld(RecursiveMutex &cs) LOCKS_EXCLUDED(cs)
    LOCK_RETURNED(cs) {
    return cs;
}
inline RecursiveMutex *MaybeCheckNotHeld(RecursiveMutex *cs) LOCKS_EXCLUDED(cs)
    LOCK_RETURNED(cs) {
    return cs;
}
 
#define LOCK(cs)                                                               \
    DebugLock<decltype(cs)> UNIQUE_LOG_NAME(criticalblock)(                    \
        MaybeCheckNotHeld(cs), #cs, __FILE__, __LINE__)
#define LOCK2(cs1, cs2)                                                        \
    DebugLock<decltype(cs1)> criticalblock1(MaybeCheckNotHeld(cs1), #cs1,      \
                                            __FILE__, __LINE__);               \
    DebugLock<decltype(cs2)> criticalblock2(MaybeCheckNotHeld(cs2), #cs2,      \
                                            __FILE__, __LINE__);
#define TRY_LOCK(cs, name)                                                     \
    DebugLock<decltype(cs)> name(MaybeCheckNotHeld(cs), #cs, __FILE__,         \
                                 __LINE__, true)
#define WAIT_LOCK(cs, name)                                                    \
    DebugLock<decltype(cs)> name(MaybeCheckNotHeld(cs), #cs, __FILE__, __LINE__)
 
#define ENTER_CRITICAL_SECTION(cs)                                             \
    {                                                                          \
        EnterCritical(#cs, __FILE__, __LINE__, &cs);                           \
        (cs).lock();                                                           \
    }
 
#define LEAVE_CRITICAL_SECTION(cs)                                             \
    {                                                                          \
        std::string lockname;                                                  \
        CheckLastCritical((void *)(&cs), lockname, #cs, __FILE__, __LINE__);   \
        (cs).unlock();                                                         \
        LeaveCritical();                                                       \
    }
 
#define WITH_LOCK(cs, code)                                                    \
    (MaybeCheckNotHeld(cs), [&]() -> decltype(auto) {                          \
        LOCK(cs);                                                              \
        code;                                                                  \
    }())
 
class CSemaphore {
private:
    std::condition_variable condition;
    std::mutex mutex;
    int value;
 
public:
    explicit CSemaphore(int init) : value(init) {}
 
    void wait() {
        std::unique_lock<std::mutex> lock(mutex);
        condition.wait(lock, [&]() { return value >= 1; });
        value--;
    }
 
    bool try_wait() {
        std::lock_guard<std::mutex> lock(mutex);
        if (value < 1) {
            return false;
        }
        value--;
        return true;
    }
 
    void post() {
        {
            std::lock_guard<std::mutex> lock(mutex);
            value++;
        }
        condition.notify_one();
    }
};
 
class CSemaphoreGrant {
private:
    CSemaphore *sem;
    bool fHaveGrant;
 
public:
    void Acquire() {
        if (fHaveGrant) {
            return;
        }
        sem->wait();
        fHaveGrant = true;
    }
 
    void Release() {
        if (!fHaveGrant) {
            return;
        }
        sem->post();
        fHaveGrant = false;
    }
 
    bool TryAcquire() {
        if (!fHaveGrant && sem->try_wait()) {
            fHaveGrant = true;
        }
        return fHaveGrant;
    }
 
    void MoveTo(CSemaphoreGrant &grant) {
        grant.Release();
        grant.sem = sem;
        grant.fHaveGrant = fHaveGrant;
        fHaveGrant = false;
    }
 
    CSemaphoreGrant() : sem(nullptr), fHaveGrant(false) {}
 
    explicit CSemaphoreGrant(CSemaphore &sema, bool fTry = false)
        : sem(&sema), fHaveGrant(false) {
        if (fTry) {
            TryAcquire();
        } else {
            Acquire();
        }
    }
 
    ~CSemaphoreGrant() { Release(); }
 
    operator bool() const { return fHaveGrant; }
};
 
#endif // BITCOIN_SYNC_H