src/sync.h

   1 // Copyright (c) 2009-2010 Satoshi Nakamoto
   2 // Copyright (c) 2009-2017 The Bitcoin Core developers
   3 // Distributed under the MIT software license, see the accompanying
   4 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
   5
   6 #ifndef BITCOIN_SYNC_H
   7 #define BITCOIN_SYNC_H
   8
   9 #include <threadsafety.h>
  10
  11 #include <condition_variable>
  12 #include <thread>
  13 #include <mutex>
  14
  15
  16 ////////////////////////////////////////////////
  17 //                                            //
  18 // THE SIMPLE DEFINITION, EXCLUDING DEBUG CODE //
  19 //                                            //
  20 ////////////////////////////////////////////////
  21
  22 /*
  23 CCriticalSection mutex;
  24     std::recursive_mutex mutex;
  25
  26 LOCK(mutex);
  27     std::unique_lock<std::recursive_mutex> criticalblock(mutex);
  28
  29 LOCK2(mutex1, mutex2);
  30     std::unique_lock<std::recursive_mutex> criticalblock1(mutex1);
  31     std::unique_lock<std::recursive_mutex> criticalblock2(mutex2);
  32
  33 TRY_LOCK(mutex, name);
  34     std::unique_lock<std::recursive_mutex> name(mutex, std::try_to_lock_t);
  35
  36 ENTER_CRITICAL_SECTION(mutex); // no RAII
  37     mutex.lock();
  38
  39 LEAVE_CRITICAL_SECTION(mutex); // no RAII
  40     mutex.unlock();
  41  */
  42
  43 ///////////////////////////////
  44 //                           //
  45 // THE ACTUAL IMPLEMENTATION //
  46 //                           //
  47 ///////////////////////////////
  48
  49 /**
  50  * Template mixin that adds -Wthread-safety locking
  51  * annotations to a subset of the mutex API.
  52  */
  53 template <typename PARENT>
  54 class LOCKABLE AnnotatedMixin : public PARENT
  55 {
  56 public:
  57     void lock() EXCLUSIVE_LOCK_FUNCTION()
  58     {
  59         PARENT::lock();
  60     }
  61
  62     void unlock() UNLOCK_FUNCTION()
  63     {
  64         PARENT::unlock();
  65     }
  66
  67     bool try_lock() EXCLUSIVE_TRYLOCK_FUNCTION(true)
  68     {
  69         return PARENT::try_lock();
  70     }
  71 };
  72
  73 #ifdef DEBUG_LOCKORDER
  74 void EnterCritical(const char* pszName, const char* pszFile, int nLine, void* cs, bool fTry = false);
  75 void LeaveCritical();
  76 std::string LocksHeld();
  77 void AssertLockHeldInternal(const char* pszName, const char* pszFile, int nLine, void* cs);
  78 void AssertLockNotHeldInternal(const char* pszName, const char* pszFile, int nLine, void* cs);
  79 void DeleteLock(void* cs);
  80 #else
  81 void static inline EnterCritical(const char* pszName, const char* pszFile, int nLine, void* cs, bool fTry = false) {}
  82 void static inline LeaveCritical() {}
  83 void static inline AssertLockHeldInternal(const char* pszName, const char* pszFile, int nLine, void* cs) {}
  84 void static inline AssertLockNotHeldInternal(const char* pszName, const char* pszFile, int nLine, void* cs) {}
  85 void static inline DeleteLock(void* cs) {}
  86 #endif
  87 #define AssertLockHeld(cs) AssertLockHeldInternal(#cs, __FILE__, __LINE__, &cs)
  88 #define AssertLockNotHeld(cs) AssertLockNotHeldInternal(#cs, __FILE__, __LINE__, &cs)
  89
  90 /**
  91  * Wrapped mutex: supports recursive locking, but no waiting
  92  * TODO: We should move away from using the recursive lock by default.
  93  */
  94 class CCriticalSection : public AnnotatedMixin<std::recursive_mutex>
  95 {
  96 public:
  97     ~CCriticalSection() {
  98         DeleteLock((void*)this);
  99     }
 100 };
 101
 102 /** Wrapped mutex: supports waiting but not recursive locking */
 103 typedef AnnotatedMixin<std::mutex> CWaitableCriticalSection;
 104
 105 /** Just a typedef for std::condition_variable, can be wrapped later if desired */
 106 typedef std::condition_variable CConditionVariable;
 107
 108 /** Just a typedef for std::unique_lock, can be wrapped later if desired */
 109 typedef std::unique_lock<std::mutex> WaitableLock;
 110
 111 #ifdef DEBUG_LOCKCONTENTION
 112 void PrintLockContention(const char* pszName, const char* pszFile, int nLine);
 113 #endif
 114
 115 /** Wrapper around std::unique_lock<CCriticalSection> */
 116 class SCOPED_LOCKABLE CCriticalBlock
 117 {
 118 private:
 119     std::unique_lock<CCriticalSection> lock;
 120
 121     void Enter(const char* pszName, const char* pszFile, int nLine)
 122     {
 123         EnterCritical(pszName, pszFile, nLine, (void*)(lock.mutex()));
 124 #ifdef DEBUG_LOCKCONTENTION
 125         if (!lock.try_lock()) {
 126             PrintLockContention(pszName, pszFile, nLine);
 127 #endif
 128             lock.lock();
 129 #ifdef DEBUG_LOCKCONTENTION
 130         }
 131 #endif
 132     }
 133
 134     bool TryEnter(const char* pszName, const char* pszFile, int nLine)
 135     {
 136         EnterCritical(pszName, pszFile, nLine, (void*)(lock.mutex()), true);
 137         lock.try_lock();
 138         if (!lock.owns_lock())
 139             LeaveCritical();
 140         return lock.owns_lock();
 141     }
 142
 143 public:
 144     CCriticalBlock(CCriticalSection& mutexIn, const char* pszName, const char* pszFile, int nLine, bool fTry = false) EXCLUSIVE_LOCK_FUNCTION(mutexIn) : lock(mutexIn, std::defer_lock)
 145     {
 146         if (fTry)
 147             TryEnter(pszName, pszFile, nLine);
 148         else
 149             Enter(pszName, pszFile, nLine);
 150     }
 151
 152     CCriticalBlock(CCriticalSection* pmutexIn, const char* pszName, const char* pszFile, int nLine, bool fTry = false) EXCLUSIVE_LOCK_FUNCTION(pmutexIn)
 153     {
 154         if (!pmutexIn) return;
 155
 156         lock = std::unique_lock<CCriticalSection>(*pmutexIn, std::defer_lock);
 157         if (fTry)
 158             TryEnter(pszName, pszFile, nLine);
 159         else
 160             Enter(pszName, pszFile, nLine);
 161     }
 162
 163     ~CCriticalBlock() UNLOCK_FUNCTION()
 164     {
 165         if (lock.owns_lock())
 166             LeaveCritical();
 167     }
 168
 169     operator bool()
 170     {
 171         return lock.owns_lock();
 172     }
 173 };
 174
 175 #define PASTE(x, y) x ## y
 176 #define PASTE2(x, y) PASTE(x, y)
 177
 178 #define LOCK(cs) CCriticalBlock PASTE2(criticalblock, __COUNTER__)(cs, #cs, __FILE__, __LINE__)
 179 #define LOCK2(cs1, cs2) CCriticalBlock criticalblock1(cs1, #cs1, __FILE__, __LINE__), criticalblock2(cs2, #cs2, __FILE__, __LINE__)
 180 #define TRY_LOCK(cs, name) CCriticalBlock name(cs, #cs, __FILE__, __LINE__, true)
 181
 182 #define ENTER_CRITICAL_SECTION(cs)                            \
 183     {                                                         \
 184         EnterCritical(#cs, __FILE__, __LINE__, (void*)(&cs)); \
 185         (cs).lock();                                          \
 186     }
 187
 188 #define LEAVE_CRITICAL_SECTION(cs) \
 189     {                              \
 190         (cs).unlock();             \
 191         LeaveCritical();           \
 192     }
 193
 194 class CSemaphore
 195 {
 196 private:
 197     std::condition_variable condition;
 198     std::mutex mutex;
 199     int value;
 200
 201 public:
 202     explicit CSemaphore(int init) : value(init) {}
 203
 204     void wait()
 205     {
 206         std::unique_lock<std::mutex> lock(mutex);
 207         condition.wait(lock, [&]() { return value >= 1; });
 208         value--;
 209     }
 210
 211     bool try_wait()
 212     {
 213         std::lock_guard<std::mutex> lock(mutex);
 214         if (value < 1)
 215             return false;
 216         value--;
 217         return true;
 218     }
 219
 220     void post()
 221     {
 222         {
 223             std::lock_guard<std::mutex> lock(mutex);
 224             value++;
 225         }
 226         condition.notify_one();
 227     }
 228 };
 229
 230 /** RAII-style semaphore lock */
 231 class CSemaphoreGrant
 232 {
 233 private:
 234     CSemaphore* sem;
 235     bool fHaveGrant;
 236
 237 public:
 238     void Acquire()
 239     {
 240         if (fHaveGrant)
 241             return;
 242         sem->wait();
 243         fHaveGrant = true;
 244     }
 245
 246     void Release()
 247     {
 248         if (!fHaveGrant)
 249             return;
 250         sem->post();
 251         fHaveGrant = false;
 252     }
 253
 254     bool TryAcquire()
 255     {
 256         if (!fHaveGrant && sem->try_wait())
 257             fHaveGrant = true;
 258         return fHaveGrant;
 259     }
 260
 261     void MoveTo(CSemaphoreGrant& grant)
 262     {
 263         grant.Release();
 264         grant.sem = sem;
 265         grant.fHaveGrant = fHaveGrant;
 266         fHaveGrant = false;
 267     }
 268
 269     CSemaphoreGrant() : sem(nullptr), fHaveGrant(false) {}
 270
 271     explicit CSemaphoreGrant(CSemaphore& sema, bool fTry = false) : sem(&sema), fHaveGrant(false)
 272     {
 273         if (fTry)
 274             TryAcquire();
 275         else
 276             Acquire();
 277     }
 278
 279     ~CSemaphoreGrant()
 280     {
 281         Release();
 282     }
 283
 284     operator bool() const
 285     {
 286         return fHaveGrant;
 287     }
 288 };
 289
 290 #endif // BITCOIN_SYNC_H