src/sync.h

   1 // Copyright (c) 2009-2010 Satoshi Nakamoto
   2 // Copyright (c) 2009-2016 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 <boost/thread/condition_variable.hpp>
  12 #include <boost/thread/mutex.hpp>
  13 #include <condition_variable>
  14 #include <thread>
  15 #include <mutex>
  16
  17
  18 ////////////////////////////////////////////////
  19 //                                            //
  20 // THE SIMPLE DEFINITION, EXCLUDING DEBUG CODE //
  21 //                                            //
  22 ////////////////////////////////////////////////
  23
  24 /*
  25 CCriticalSection mutex;
  26     std::recursive_mutex mutex;
  27
  28 LOCK(mutex);
  29     std::unique_lock<std::recursive_mutex> criticalblock(mutex);
  30
  31 LOCK2(mutex1, mutex2);
  32     std::unique_lock<std::recursive_mutex> criticalblock1(mutex1);
  33     std::unique_lock<std::recursive_mutex> criticalblock2(mutex2);
  34
  35 TRY_LOCK(mutex, name);
  36     std::unique_lock<std::recursive_mutex> name(mutex, std::try_to_lock_t);
  37
  38 ENTER_CRITICAL_SECTION(mutex); // no RAII
  39     mutex.lock();
  40
  41 LEAVE_CRITICAL_SECTION(mutex); // no RAII
  42     mutex.unlock();
  43  */
  44
  45 ///////////////////////////////
  46 //                           //
  47 // THE ACTUAL IMPLEMENTATION //
  48 //                           //
  49 ///////////////////////////////
  50
  51 /**
  52  * Template mixin that adds -Wthread-safety locking
  53  * annotations to a subset of the mutex API.
  54  */
  55 template <typename PARENT>
  56 class LOCKABLE AnnotatedMixin : public PARENT
  57 {
  58 public:
  59     void lock() EXCLUSIVE_LOCK_FUNCTION()
  60     {
  61         PARENT::lock();
  62     }
  63
  64     void unlock() UNLOCK_FUNCTION()
  65     {
  66         PARENT::unlock();
  67     }
  68
  69     bool try_lock() EXCLUSIVE_TRYLOCK_FUNCTION(true)
  70     {
  71         return PARENT::try_lock();
  72     }
  73 };
  74
  75 #ifdef DEBUG_LOCKORDER
  76 void EnterCritical(const char* pszName, const char* pszFile, int nLine, void* cs, bool fTry = false);
  77 void LeaveCritical();
  78 std::string LocksHeld();
  79 void AssertLockHeldInternal(const char* pszName, const char* pszFile, int nLine, void* cs);
  80 void DeleteLock(void* cs);
  81 #else
  82 void static inline EnterCritical(const char* pszName, const char* pszFile, int nLine, void* cs, bool fTry = false) {}
  83 void static inline LeaveCritical() {}
  84 void static inline AssertLockHeldInternal(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
  89 /**
  90  * Wrapped mutex: supports recursive locking, but no waiting
  91  * TODO: We should move away from using the recursive lock by default.
  92  */
  93 class CCriticalSection : public AnnotatedMixin<std::recursive_mutex>
  94 {
  95 public:
  96     ~CCriticalSection() {
  97         DeleteLock((void*)this);
  98     }
  99 };
 100
 101 /** Wrapped mutex: supports waiting but not recursive locking */
 102 typedef AnnotatedMixin<std::mutex> CWaitableCriticalSection;
 103
 104 /** Just a typedef for std::condition_variable, can be wrapped later if desired */
 105 typedef std::condition_variable CConditionVariable;
 106
 107 /** Just a typedef for std::unique_lock, can be wrapped later if desired */
 108 typedef std::unique_lock<std::mutex> WaitableLock;
 109
 110 #ifdef DEBUG_LOCKCONTENTION
 111 void PrintLockContention(const char* pszName, const char* pszFile, int nLine);
 112 #endif
 113
 114 /** Wrapper around std::unique_lock<CCriticalSection> */
 115 class SCOPED_LOCKABLE CCriticalBlock
 116 {
 117 private:
 118     std::unique_lock<CCriticalSection> lock;
 119
 120     void Enter(const char* pszName, const char* pszFile, int nLine)
 121     {
 122         EnterCritical(pszName, pszFile, nLine, (void*)(lock.mutex()));
 123 #ifdef DEBUG_LOCKCONTENTION
 124         if (!lock.try_lock()) {
 125             PrintLockContention(pszName, pszFile, nLine);
 126 #endif
 127             lock.lock();
 128 #ifdef DEBUG_LOCKCONTENTION
 129         }
 130 #endif
 131     }
 132
 133     bool TryEnter(const char* pszName, const char* pszFile, int nLine)
 134     {
 135         EnterCritical(pszName, pszFile, nLine, (void*)(lock.mutex()), true);
 136         lock.try_lock();
 137         if (!lock.owns_lock())
 138             LeaveCritical();
 139         return lock.owns_lock();
 140     }
 141
 142 public:
 143     CCriticalBlock(CCriticalSection& mutexIn, const char* pszName, const char* pszFile, int nLine, bool fTry = false) EXCLUSIVE_LOCK_FUNCTION(mutexIn) : lock(mutexIn, std::defer_lock)
 144     {
 145         if (fTry)
 146             TryEnter(pszName, pszFile, nLine);
 147         else
 148             Enter(pszName, pszFile, nLine);
 149     }
 150
 151     CCriticalBlock(CCriticalSection* pmutexIn, const char* pszName, const char* pszFile, int nLine, bool fTry = false) EXCLUSIVE_LOCK_FUNCTION(pmutexIn)
 152     {
 153         if (!pmutexIn) return;
 154
 155         lock = std::unique_lock<CCriticalSection>(*pmutexIn, std::defer_lock);
 156         if (fTry)
 157             TryEnter(pszName, pszFile, nLine);
 158         else
 159             Enter(pszName, pszFile, nLine);
 160     }
 161
 162     ~CCriticalBlock() UNLOCK_FUNCTION()
 163     {
 164         if (lock.owns_lock())
 165             LeaveCritical();
 166     }
 167
 168     operator bool()
 169     {
 170         return lock.owns_lock();
 171     }
 172 };
 173
 174 #define PASTE(x, y) x ## y
 175 #define PASTE2(x, y) PASTE(x, y)
 176
 177 #define LOCK(cs) CCriticalBlock PASTE2(criticalblock, __COUNTER__)(cs, #cs, __FILE__, __LINE__)
 178 #define LOCK2(cs1, cs2) CCriticalBlock criticalblock1(cs1, #cs1, __FILE__, __LINE__), criticalblock2(cs2, #cs2, __FILE__, __LINE__)
 179 #define TRY_LOCK(cs, name) CCriticalBlock name(cs, #cs, __FILE__, __LINE__, true)
 180
 181 #define ENTER_CRITICAL_SECTION(cs)                            \
 182     {                                                         \
 183         EnterCritical(#cs, __FILE__, __LINE__, (void*)(&cs)); \
 184         (cs).lock();                                          \
 185     }
 186
 187 #define LEAVE_CRITICAL_SECTION(cs) \
 188     {                              \
 189         (cs).unlock();             \
 190         LeaveCritical();           \
 191     }
 192
 193 class CSemaphore
 194 {
 195 private:
 196     boost::condition_variable condition;
 197     boost::mutex mutex;
 198     int value;
 199
 200 public:
 201     explicit CSemaphore(int init) : value(init) {}
 202
 203     void wait()
 204     {
 205         boost::unique_lock<boost::mutex> lock(mutex);
 206         while (value < 1) {
 207             condition.wait(lock);
 208         }
 209         value--;
 210     }
 211
 212     bool try_wait()
 213     {
 214         boost::unique_lock<boost::mutex> lock(mutex);
 215         if (value < 1)
 216             return false;
 217         value--;
 218         return true;
 219     }
 220
 221     void post()
 222     {
 223         {
 224             boost::unique_lock<boost::mutex> lock(mutex);
 225             value++;
 226         }
 227         condition.notify_one();
 228     }
 229 };
 230
 231 /** RAII-style semaphore lock */
 232 class CSemaphoreGrant
 233 {
 234 private:
 235     CSemaphore* sem;
 236     bool fHaveGrant;
 237
 238 public:
 239     void Acquire()
 240     {
 241         if (fHaveGrant)
 242             return;
 243         sem->wait();
 244         fHaveGrant = true;
 245     }
 246
 247     void Release()
 248     {
 249         if (!fHaveGrant)
 250             return;
 251         sem->post();
 252         fHaveGrant = false;
 253     }
 254
 255     bool TryAcquire()
 256     {
 257         if (!fHaveGrant && sem->try_wait())
 258             fHaveGrant = true;
 259         return fHaveGrant;
 260     }
 261
 262     void MoveTo(CSemaphoreGrant& grant)
 263     {
 264         grant.Release();
 265         grant.sem = sem;
 266         grant.fHaveGrant = fHaveGrant;
 267         fHaveGrant = false;
 268     }
 269
 270     CSemaphoreGrant() : sem(nullptr), fHaveGrant(false) {}
 271
 272     explicit CSemaphoreGrant(CSemaphore& sema, bool fTry = false) : sem(&sema), fHaveGrant(false)
 273     {
 274         if (fTry)
 275             TryAcquire();
 276         else
 277             Acquire();
 278     }
 279
 280     ~CSemaphoreGrant()
 281     {
 282         Release();
 283     }
 284
 285     operator bool() const
 286     {
 287         return fHaveGrant;
 288     }
 289 };
 290
 291 #endif // BITCOIN_SYNC_H