// Copyright (c) 2011-2015 The Bitcoin 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/foreach.hpp> #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)" : ""); } std::string MutexName() const { return mutexName; } 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) { // We attempt to not assert on probably-not deadlocks by assuming that // a try lock will immediately have otherwise bailed if it had // failed to get the lock // We do this by, for the locks which triggered the potential deadlock, // in either lockorder, checking that the second of the two which is locked // is only a TRY_LOCK, ignoring locks if they are reentrant. bool firstLocked = false; bool secondLocked = false; bool onlyMaybeDeadlock = false; LogPrintf("POTENTIAL DEADLOCK DETECTED\n"); LogPrintf("Previous lock order was:\n"); BOOST_FOREACH (const PAIRTYPE(void*, CLockLocation) & i, s2) { if (i.first == mismatch.first) { LogPrintf(" (1)"); if (!firstLocked && secondLocked && i.second.fTry) onlyMaybeDeadlock = true; firstLocked = true; } if (i.first == mismatch.second) { LogPrintf(" (2)"); if (!secondLocked && firstLocked && i.second.fTry) onlyMaybeDeadlock = true; secondLocked = true; } LogPrintf(" %s\n", i.second.ToString()); } firstLocked = false; secondLocked = false; LogPrintf("Current lock order is:\n"); BOOST_FOREACH (const PAIRTYPE(void*, CLockLocation) & i, s1) { if (i.first == mismatch.first) { LogPrintf(" (1)"); if (!firstLocked && secondLocked && i.second.fTry) onlyMaybeDeadlock = true; firstLocked = true; } if (i.first == mismatch.second) { LogPrintf(" (2)"); if (!secondLocked && firstLocked && i.second.fTry) onlyMaybeDeadlock = true; secondLocked = true; } LogPrintf(" %s\n", i.second.ToString()); } assert(onlyMaybeDeadlock); } static void push_lock(void* c, const CLockLocation& locklocation, bool fTry) { if (lockstack.get() == NULL) lockstack.reset(new LockStack); boost::unique_lock<boost::mutex> lock(lockdata.dd_mutex); (*lockstack).push_back(std::make_pair(c, locklocation)); if (!fTry) { BOOST_FOREACH (const PAIRTYPE(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), fTry); } void LeaveCritical() { pop_lock(); } std::string LocksHeld() { std::string result; BOOST_FOREACH (const PAIRTYPE(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) { BOOST_FOREACH (const PAIRTYPE(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, (void*)0); 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 */