text: // Copyright (c) 2012-2018 The Bitcoin Core developers
  // Copyright (c) 2017 The Raven Core developers
  // Copyright (c) 2018 The Rito Core developers
  // Copyright (c) 2020 The KringleProjectCoin Core developers
  // Distributed under the MIT software license, see the accompanying
  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
  
  #include "sync.h"
  
  #include "util.h"
  #include "utilstrencodings.h"
  
  #include <stdio.h>
  
  #include <boost/thread.hpp>
  
  #ifdef DEBUG_LOCKCONTENTION
  void PrintLockContention(const char* pszName, const char* pszFile, int nLine)
  {
      LogPrintf("LOCKCONTENTION: %s\n", pszName);
      LogPrintf("Locker: %s:%d\n", pszFile, nLine);
  }
  #endif /* DEBUG_LOCKCONTENTION */
  
  #ifdef DEBUG_LOCKORDER
  //
  // Early deadlock detection.
  // Problem being solved:
  //    Thread 1 locks  A, then B, then C
  //    Thread 2 locks  D, then C, then A
  //     --> may result in deadlock between the two threads, depending on when they run.
  // Solution implemented here:
  // Keep track of pairs of locks: (A before B), (A before C), etc.
  // Complain if any thread tries to lock in a different order.
  //
  
  struct CLockLocation {
      CLockLocation(const char* pszName, const char* pszFile, int nLine, bool fTryIn)
      {
          mutexName = pszName;
          sourceFile = pszFile;
          sourceLine = nLine;
          fTry = fTryIn;
      }
  
      std::string ToString() const
      {
          return mutexName + "  " + sourceFile + ":" + itostr(sourceLine) + (fTry ? " (TRY)" : "");
      }
  
      bool fTry;
  private:
      std::string mutexName;
      std::string sourceFile;
      int sourceLine;
  };
  
  typedef std::vector<std::pair<void*, CLockLocation> > LockStack;
  typedef std::map<std::pair<void*, void*>, LockStack> LockOrders;
  typedef std::set<std::pair<void*, void*> > InvLockOrders;
  
  struct LockData {
      // Very ugly hack: as the global constructs and destructors run single
      // threaded, we use this boolean to know whether LockData still exists,
      // as DeleteLock can get called by global CCriticalSection destructors
      // after LockData disappears.
      bool available;
      LockData() : available(true) {}
      ~LockData() { available = false; }
  
      LockOrders lockorders;
      InvLockOrders invlockorders;
      boost::mutex dd_mutex;
  } static lockdata;
  
  boost::thread_specific_ptr<LockStack> lockstack;
  
  static void potential_deadlock_detected(const std::pair<void*, void*>& mismatch, const LockStack& s1, const LockStack& s2)
  {
      LogPrintf("POTENTIAL DEADLOCK DETECTED\n");
      LogPrintf("Previous lock order was:\n");
      for (const std::pair<void*, CLockLocation> & i : s2) {
          if (i.first == mismatch.first) {
              LogPrintf(" (1)");
          }
          if (i.first == mismatch.second) {
              LogPrintf(" (2)");
          }
          LogPrintf(" %s\n", i.second.ToString());
      }
      LogPrintf("Current lock order is:\n");
      for (const std::pair<void*, CLockLocation> & i : s1) {
          if (i.first == mismatch.first) {
              LogPrintf(" (1)");
          }
          if (i.first == mismatch.second) {
              LogPrintf(" (2)");
          }
          LogPrintf(" %s\n", i.second.ToString());
      }
      assert(false);
  }
  
  static void push_lock(void* c, const CLockLocation& locklocation)
  {
      if (lockstack.get() == nullptr)
          lockstack.reset(new LockStack);
  
      boost::unique_lock<boost::mutex> lock(lockdata.dd_mutex);
  
      (*lockstack).push_back(std::make_pair(c, locklocation));
  
      for (const std::pair<void*, CLockLocation> & i : (*lockstack)) {
          if (i.first == c)
              break;
  
          std::pair<void*, void*> p1 = std::make_pair(i.first, c);
          if (lockdata.lockorders.count(p1))
              continue;
          lockdata.lockorders[p1] = (*lockstack);
  
          std::pair<void*, void*> p2 = std::make_pair(c, i.first);
          lockdata.invlockorders.insert(p2);
          if (lockdata.lockorders.count(p2))
              potential_deadlock_detected(p1, lockdata.lockorders[p2], lockdata.lockorders[p1]);
      }
  }
  
  static void pop_lock()
  {
      (*lockstack).pop_back();
  }
  
  void EnterCritical(const char* pszName, const char* pszFile, int nLine, void* cs, bool fTry)
  {
      push_lock(cs, CLockLocation(pszName, pszFile, nLine, fTry));
  }
  
  void LeaveCritical()
  {
      pop_lock();
  }
  
  std::string LocksHeld()
  {
      std::string result;
      for (const std::pair<void*, CLockLocation> & i : *lockstack)
          result += i.second.ToString() + std::string("\n");
      return result;
  }
  
  void AssertLockHeldInternal(const char* pszName, const char* pszFile, int nLine, void* cs)
  {
      for (const std::pair<void*, CLockLocation> & i : *lockstack)
          if (i.first == cs)
              return;
      fprintf(stderr, "Assertion failed: lock %s not held in %s:%i; locks held:\n%s", pszName, pszFile, nLine, LocksHeld().c_str());
      abort();
  }
  
  void DeleteLock(void* cs)
  {
      if (!lockdata.available) {
          // We're already shutting down.
          return;
      }
      boost::unique_lock<boost::mutex> lock(lockdata.dd_mutex);
      std::pair<void*, void*> item = std::make_pair(cs, nullptr);
      LockOrders::iterator it = lockdata.lockorders.lower_bound(item);
      while (it != lockdata.lockorders.end() && it->first.first == cs) {
          std::pair<void*, void*> invitem = std::make_pair(it->first.second, it->first.first);
          lockdata.invlockorders.erase(invitem);
          lockdata.lockorders.erase(it++);
      }
      InvLockOrders::iterator invit = lockdata.invlockorders.lower_bound(item);
      while (invit != lockdata.invlockorders.end() && invit->first == cs) {
          std::pair<void*, void*> invinvitem = std::make_pair(invit->second, invit->first);
          lockdata.lockorders.erase(invinvitem);
          lockdata.invlockorders.erase(invit++);
      }
  }
  
  #endif /* DEBUG_LOCKORDER */
  