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/locks.hpp>
  13 #include <boost/thread/mutex.hpp>
  14 #include <boost/thread/recursive_mutex.hpp>
  15
  16
  17 ////////////////////////////////////////////////
  18 //                                            //
  19 // THE SIMPLE DEFINITION, EXCLUDING DEBUG CODE //
  20 //                                            //
  21 ////////////////////////////////////////////////
  22
  23 /*
  24 CCriticalSection mutex;
  25     boost::recursive_mutex mutex;
  26
  27 LOCK(mutex);
  28     boost::unique_lock<boost::recursive_mutex> criticalblock(mutex);
  29
  30 LOCK2(mutex1, mutex2);
  31     boost::unique_lock<boost::recursive_mutex> criticalblock1(mutex1);
  32     boost::unique_lock<boost::recursive_mutex> criticalblock2(mutex2);
  33
  34 TRY_LOCK(mutex, name);
  35     boost::unique_lock<boost::recursive_mutex> name(mutex, boost::try_to_lock_t);
  36
  37 ENTER_CRITICAL_SECTION(mutex); // no RAII
  38     mutex.lock();
  39
  40 LEAVE_CRITICAL_SECTION(mutex); // no RAII
  41     mutex.unlock();
  42  */
  43
  44 ///////////////////////////////
  45 //                           //
  46 // THE ACTUAL IMPLEMENTATION //
  47 //                           //
  48 ///////////////////////////////
  49
  50 /**
  51  * Template mixin that adds -Wthread-safety locking
  52  * annotations to a subset of the mutex API.
  53  */
  54 template <typename PARENT>
  55 class LOCKABLE AnnotatedMixin : public PARENT
  56 {
  57 public:
  58     void lock() EXCLUSIVE_LOCK_FUNCTION()
  59     {
  60         PARENT::lock();
  61     }
  62
  63     void unlock() UNLOCK_FUNCTION()
  64     {
  65         PARENT::unlock();
  66     }
  67
  68     bool try_lock() EXCLUSIVE_TRYLOCK_FUNCTION(true)
  69     {
  70         return PARENT::try_lock();
  71     }
  72 };
  73
  74 #ifdef DEBUG_LOCKORDER
  75 void EnterCritical(const char* pszName, const char* pszFile, int nLine, void* cs, bool fTry = false);
  76 void LeaveCritical();
  77 std::string LocksHeld();
  78 void AssertLockHeldInternal(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 DeleteLock(void* cs) {}
  85 #endif
  86 #define AssertLockHeld(cs) AssertLockHeldInternal(#cs, __FILE__, __LINE__, &cs)
  87
  88 /**
  89  * Wrapped boost mutex: supports recursive locking, but no waiting
  90  * TODO: We should move away from using the recursive lock by default.
  91  */
  92 class CCriticalSection : public AnnotatedMixin<boost::recursive_mutex>
  93 {
  94 public:
  95     ~CCriticalSection() {
  96         DeleteLock((void*)this);
  97     }
  98 };
  99
 100 typedef CCriticalSection CDynamicCriticalSection;
 101 /** Wrapped boost mutex: supports waiting but not recursive locking */
 102 typedef AnnotatedMixin<boost::mutex> CWaitableCriticalSection;
 103
 104 /** Just a typedef for boost::condition_variable, can be wrapped later if desired */
 105 typedef boost::condition_variable CConditionVariable;
 106
 107 #ifdef DEBUG_LOCKCONTENTION
 108 void PrintLockContention(const char* pszName, const char* pszFile, int nLine);
 109 #endif
 110
 111 /** Wrapper around boost::unique_lock<Mutex> */
 112 template <typename Mutex>
 113 class SCOPED_LOCKABLE CMutexLock
 114 {
 115 private:
 116     boost::unique_lock<Mutex> lock;
 117
 118     void Enter(const char* pszName, const char* pszFile, int nLine)
 119     {
 120         EnterCritical(pszName, pszFile, nLine, (void*)(lock.mutex()));
 121 #ifdef DEBUG_LOCKCONTENTION
 122         if (!lock.try_lock()) {
 123             PrintLockContention(pszName, pszFile, nLine);
 124 #endif
 125             lock.lock();
 126 #ifdef DEBUG_LOCKCONTENTION
 127         }
 128 #endif
 129     }
 130
 131     bool TryEnter(const char* pszName, const char* pszFile, int nLine)
 132     {
 133         EnterCritical(pszName, pszFile, nLine, (void*)(lock.mutex()), true);
 134         lock.try_lock();
 135         if (!lock.owns_lock())
 136             LeaveCritical();
 137         return lock.owns_lock();
 138     }
 139
 140 public:
 141     CMutexLock(Mutex& mutexIn, const char* pszName, const char* pszFile, int nLine, bool fTry = false) EXCLUSIVE_LOCK_FUNCTION(mutexIn) : lock(mutexIn, boost::defer_lock)
 142     {
 143         if (fTry)
 144             TryEnter(pszName, pszFile, nLine);
 145         else
 146             Enter(pszName, pszFile, nLine);
 147     }
 148
 149     CMutexLock(Mutex* pmutexIn, const char* pszName, const char* pszFile, int nLine, bool fTry = false) EXCLUSIVE_LOCK_FUNCTION(pmutexIn)
 150     {
 151         if (!pmutexIn) return;
 152
 153         lock = boost::unique_lock<Mutex>(*pmutexIn, boost::defer_lock);
 154         if (fTry)
 155             TryEnter(pszName, pszFile, nLine);
 156         else
 157             Enter(pszName, pszFile, nLine);
 158     }
 159
 160     ~CMutexLock() UNLOCK_FUNCTION()
 161     {
 162         if (lock.owns_lock())
 163             LeaveCritical();
 164     }
 165
 166     operator bool()
 167     {
 168         return lock.owns_lock();
 169     }
 170 };
 171
 172 typedef CMutexLock<CCriticalSection> CCriticalBlock;
 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     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(NULL), fHaveGrant(false) {}
 271
 272     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()
 286     {
 287         return fHaveGrant;
 288     }
 289 };
 290
 291 #endif // BITCOIN_SYNC_H