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// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2022 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();
/**
* Call abort() if a potential lock order deadlock bug is detected, instead of
* just logging information and throwing a logic_error. Defaults to true, and
* set to false in DEBUG_LOCKORDER unit tests.
*/
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 mixin that adds -Wthread-safety locking annotations and lock order
* checking to a subset of the mutex API.
*/
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 unique_lock = std::unique_lock<PARENT>;
#ifdef __clang__
//! For negative capabilities in the Clang Thread Safety Analysis.
//! A negative requirement uses the EXCLUSIVE_LOCKS_REQUIRED attribute, in conjunction
//! with the ! operator, to indicate that a mutex should not be held.
const AnnotatedMixin& operator!() const { return *this; }
#endif // __clang__
};
/**
* Wrapped mutex: supports recursive locking, but no waiting
* TODO: We should move away from using the recursive lock by default.
*/
using RecursiveMutex = AnnotatedMixin<std::recursive_mutex>;
/** Wrapped mutex: supports waiting but not recursive locking */
using Mutex = AnnotatedMixin<std::mutex>;
/** Different type to mark Mutex at global scope
*
* Thread safety analysis can't handle negative assertions about mutexes
* with global scope well, so mark them with a separate type, and
* eventually move all the mutexes into classes so they are not globally
* visible.
*
* See: https://github.com/bitcoin/bitcoin/pull/20272#issuecomment-720755781
*/
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)
/** Wrapper around std::unique_lock style lock for MutexType. */
template <typename MutexType>
class SCOPED_LOCKABLE UniqueLock : public MutexType::unique_lock
{
private:
using Base = typename MutexType::unique_lock;
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(MutexType& 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(MutexType* 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:
/**
* An RAII-style reverse lock. Unlocks on construction and locks on destruction.
*/
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_NAME(revlock)(g, #g, __FILE__, __LINE__)
// 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 or RecursiveMutex, just check it is not
// locked in the surrounding scope.
template <typename MutexType>
inline MutexType& MaybeCheckNotHeld(MutexType& m) LOCKS_EXCLUDED(m) LOCK_RETURNED(m) { return m; }
template <typename MutexType>
inline MutexType* MaybeCheckNotHeld(MutexType* m) LOCKS_EXCLUDED(m) LOCK_RETURNED(m) { return m; }
#define LOCK(cs) UniqueLock UNIQUE_NAME(criticalblock)(MaybeCheckNotHeld(cs), #cs, __FILE__, __LINE__)
#define LOCK2(cs1, cs2) \
UniqueLock criticalblock1(MaybeCheckNotHeld(cs1), #cs1, __FILE__, __LINE__); \
UniqueLock criticalblock2(MaybeCheckNotHeld(cs2), #cs2, __FILE__, __LINE__)
#define TRY_LOCK(cs, name) UniqueLock name(MaybeCheckNotHeld(cs), #cs, __FILE__, __LINE__, true)
#define WAIT_LOCK(cs, name) UniqueLock 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(); \
}
//! Run code while locking a mutex.
//!
//! Examples:
//!
//! WITH_LOCK(cs, shared_val = shared_val + 1);
//!
//! int val = WITH_LOCK(cs, return shared_val);
//!
//! Note:
//!
//! Since the return type deduction follows that of decltype(auto), while the
//! deduced type of:
//!
//! WITH_LOCK(cs, return {int i = 1; return i;});
//!
//! is int, the deduced type of:
//!
//! WITH_LOCK(cs, return {int j = 1; return (j);});
//!
//! is &int, a reference to a local variable
//!
//! The above is detectable at compile-time with the -Wreturn-local-addr flag in
//! gcc and the -Wreturn-stack-address flag in clang, both enabled by default.
#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();
}
};
/** RAII-style semaphore lock */
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
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