src/sync.cpp

   1 // Copyright (c) 2011-2017 The Bitcoin Core developers
   2 // Distributed under the MIT software license, see the accompanying
   3 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
   4
   5 #include <sync.h>
   6
   7 #include <set>
   8 #include <util.h>
   9 #include <utilstrencodings.h>
  10
  11 #include <stdio.h>
  12
  13 #ifdef DEBUG_LOCKCONTENTION
  14 #if !defined(HAVE_THREAD_LOCAL)
  15 static_assert(false, "thread_local is not supported");
  16 #endif
  17 void PrintLockContention(const char* pszName, const char* pszFile, int nLine)
  18 {
  19     LogPrintf("LOCKCONTENTION: %s\n", pszName);
  20     LogPrintf("Locker: %s:%d\n", pszFile, nLine);
  21 }
  22 #endif /* DEBUG_LOCKCONTENTION */
  23
  24 #ifdef DEBUG_LOCKORDER
  25 //
  26 // Early deadlock detection.
  27 // Problem being solved:
  28 //    Thread 1 locks  A, then B, then C
  29 //    Thread 2 locks  D, then C, then A
  30 //     --> may result in deadlock between the two threads, depending on when they run.
  31 // Solution implemented here:
  32 // Keep track of pairs of locks: (A before B), (A before C), etc.
  33 // Complain if any thread tries to lock in a different order.
  34 //
  35
  36 struct CLockLocation {
  37     CLockLocation(const char* pszName, const char* pszFile, int nLine, bool fTryIn)
  38     {
  39         mutexName = pszName;
  40         sourceFile = pszFile;
  41         sourceLine = nLine;
  42         fTry = fTryIn;
  43     }
  44
  45     std::string ToString() const
  46     {
  47         return mutexName + "  " + sourceFile + ":" + itostr(sourceLine) + (fTry ? " (TRY)" : "");
  48     }
  49
  50 private:
  51     bool fTry;
  52     std::string mutexName;
  53     std::string sourceFile;
  54     int sourceLine;
  55 };
  56
  57 typedef std::vector<std::pair<void*, CLockLocation> > LockStack;
  58 typedef std::map<std::pair<void*, void*>, LockStack> LockOrders;
  59 typedef std::set<std::pair<void*, void*> > InvLockOrders;
  60
  61 struct LockData {
  62     // Very ugly hack: as the global constructs and destructors run single
  63     // threaded, we use this boolean to know whether LockData still exists,
  64     // as DeleteLock can get called by global CCriticalSection destructors
  65     // after LockData disappears.
  66     bool available;
  67     LockData() : available(true) {}
  68     ~LockData() { available = false; }
  69
  70     LockOrders lockorders;
  71     InvLockOrders invlockorders;
  72     std::mutex dd_mutex;
  73 } static lockdata;
  74
  75 static thread_local std::unique_ptr<LockStack> lockstack;
  76
  77 static void potential_deadlock_detected(const std::pair<void*, void*>& mismatch, const LockStack& s1, const LockStack& s2)
  78 {
  79     LogPrintf("POTENTIAL DEADLOCK DETECTED\n");
  80     LogPrintf("Previous lock order was:\n");
  81     for (const std::pair<void*, CLockLocation> & i : s2) {
  82         if (i.first == mismatch.first) {
  83             LogPrintf(" (1)");
  84         }
  85         if (i.first == mismatch.second) {
  86             LogPrintf(" (2)");
  87         }
  88         LogPrintf(" %s\n", i.second.ToString());
  89     }
  90     LogPrintf("Current lock order is:\n");
  91     for (const std::pair<void*, CLockLocation> & i : s1) {
  92         if (i.first == mismatch.first) {
  93             LogPrintf(" (1)");
  94         }
  95         if (i.first == mismatch.second) {
  96             LogPrintf(" (2)");
  97         }
  98         LogPrintf(" %s\n", i.second.ToString());
  99     }
 100     assert(false);
 101 }
 102
 103 static void push_lock(void* c, const CLockLocation& locklocation)
 104 {
 105     if (!lockstack)
 106         lockstack.reset(new LockStack);
 107
 108     std::lock_guard<std::mutex> lock(lockdata.dd_mutex);
 109
 110     lockstack->push_back(std::make_pair(c, locklocation));
 111
 112     for (const std::pair<void*, CLockLocation> & i : (*lockstack)) {
 113         if (i.first == c)
 114             break;
 115
 116         std::pair<void*, void*> p1 = std::make_pair(i.first, c);
 117         if (lockdata.lockorders.count(p1))
 118             continue;
 119         lockdata.lockorders[p1] = (*lockstack);
 120
 121         std::pair<void*, void*> p2 = std::make_pair(c, i.first);
 122         lockdata.invlockorders.insert(p2);
 123         if (lockdata.lockorders.count(p2))
 124             potential_deadlock_detected(p1, lockdata.lockorders[p2], lockdata.lockorders[p1]);
 125     }
 126 }
 127
 128 static void pop_lock()
 129 {
 130     (*lockstack).pop_back();
 131 }
 132
 133 void EnterCritical(const char* pszName, const char* pszFile, int nLine, void* cs, bool fTry)
 134 {
 135     push_lock(cs, CLockLocation(pszName, pszFile, nLine, fTry));
 136 }
 137
 138 void LeaveCritical()
 139 {
 140     pop_lock();
 141 }
 142
 143 std::string LocksHeld()
 144 {
 145     std::string result;
 146     for (const std::pair<void*, CLockLocation> & i : *lockstack)
 147         result += i.second.ToString() + std::string("\n");
 148     return result;
 149 }
 150
 151 void AssertLockHeldInternal(const char* pszName, const char* pszFile, int nLine, void* cs)
 152 {
 153     for (const std::pair<void*, CLockLocation> & i : *lockstack)
 154         if (i.first == cs)
 155             return;
 156     fprintf(stderr, "Assertion failed: lock %s not held in %s:%i; locks held:\n%s", pszName, pszFile, nLine, LocksHeld().c_str());
 157     abort();
 158 }
 159
 160 void AssertLockNotHeldInternal(const char* pszName, const char* pszFile, int nLine, void* cs)
 161 {
 162     for (const std::pair<void*, CLockLocation>& i : *lockstack) {
 163         if (i.first == cs) {
 164             fprintf(stderr, "Assertion failed: lock %s held in %s:%i; locks held:\n%s", pszName, pszFile, nLine, LocksHeld().c_str());
 165             abort();
 166         }
 167     }
 168 }
 169
 170 void DeleteLock(void* cs)
 171 {
 172     if (!lockdata.available) {
 173         // We're already shutting down.
 174         return;
 175     }
 176     std::lock_guard<std::mutex> lock(lockdata.dd_mutex);
 177     std::pair<void*, void*> item = std::make_pair(cs, nullptr);
 178     LockOrders::iterator it = lockdata.lockorders.lower_bound(item);
 179     while (it != lockdata.lockorders.end() && it->first.first == cs) {
 180         std::pair<void*, void*> invitem = std::make_pair(it->first.second, it->first.first);
 181         lockdata.invlockorders.erase(invitem);
 182         lockdata.lockorders.erase(it++);
 183     }
 184     InvLockOrders::iterator invit = lockdata.invlockorders.lower_bound(item);
 185     while (invit != lockdata.invlockorders.end() && invit->first == cs) {
 186         std::pair<void*, void*> invinvitem = std::make_pair(invit->second, invit->first);
 187         lockdata.lockorders.erase(invinvitem);
 188         lockdata.invlockorders.erase(invit++);
 189     }
 190 }
 191
 192 #endif /* DEBUG_LOCKORDER */