src/sync.cpp

   1 // Copyright (c) 2011-2016 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 "util.h"
   8 #include "utilstrencodings.h"
   9
  10 #include <stdio.h>
  11
  12 #include <boost/thread.hpp>
  13
  14 #ifdef DEBUG_LOCKCONTENTION
  15 void PrintLockContention(const char* pszName, const char* pszFile, int nLine)
  16 {
  17     LogPrintf("LOCKCONTENTION: %s\n", pszName);
  18     LogPrintf("Locker: %s:%d\n", pszFile, nLine);
  19 }
  20 #endif /* DEBUG_LOCKCONTENTION */
  21
  22 #ifdef DEBUG_LOCKORDER
  23 //
  24 // Early deadlock detection.
  25 // Problem being solved:
  26 //    Thread 1 locks  A, then B, then C
  27 //    Thread 2 locks  D, then C, then A
  28 //     --> may result in deadlock between the two threads, depending on when they run.
  29 // Solution implemented here:
  30 // Keep track of pairs of locks: (A before B), (A before C), etc.
  31 // Complain if any thread tries to lock in a different order.
  32 //
  33
  34 struct CLockLocation {
  35     CLockLocation(const char* pszName, const char* pszFile, int nLine, bool fTryIn)
  36     {
  37         mutexName = pszName;
  38         sourceFile = pszFile;
  39         sourceLine = nLine;
  40         fTry = fTryIn;
  41     }
  42
  43     std::string ToString() const
  44     {
  45         return mutexName + "  " + sourceFile + ":" + itostr(sourceLine) + (fTry ? " (TRY)" : "");
  46     }
  47
  48     bool fTry;
  49 private:
  50     std::string mutexName;
  51     std::string sourceFile;
  52     int sourceLine;
  53 };
  54
  55 typedef std::vector<std::pair<void*, CLockLocation> > LockStack;
  56 typedef std::map<std::pair<void*, void*>, LockStack> LockOrders;
  57 typedef std::set<std::pair<void*, void*> > InvLockOrders;
  58
  59 struct LockData {
  60     // Very ugly hack: as the global constructs and destructors run single
  61     // threaded, we use this boolean to know whether LockData still exists,
  62     // as DeleteLock can get called by global CCriticalSection destructors
  63     // after LockData disappears.
  64     bool available;
  65     LockData() : available(true) {}
  66     ~LockData() { available = false; }
  67
  68     LockOrders lockorders;
  69     InvLockOrders invlockorders;
  70     boost::mutex dd_mutex;
  71 } static lockdata;
  72
  73 boost::thread_specific_ptr<LockStack> lockstack;
  74
  75 static void potential_deadlock_detected(const std::pair<void*, void*>& mismatch, const LockStack& s1, const LockStack& s2)
  76 {
  77     LogPrintf("POTENTIAL DEADLOCK DETECTED\n");
  78     LogPrintf("Previous lock order was:\n");
  79     for (const std::pair<void*, CLockLocation> & i : s2) {
  80         if (i.first == mismatch.first) {
  81             LogPrintf(" (1)");
  82         }
  83         if (i.first == mismatch.second) {
  84             LogPrintf(" (2)");
  85         }
  86         LogPrintf(" %s\n", i.second.ToString());
  87     }
  88     LogPrintf("Current lock order is:\n");
  89     for (const std::pair<void*, CLockLocation> & i : s1) {
  90         if (i.first == mismatch.first) {
  91             LogPrintf(" (1)");
  92         }
  93         if (i.first == mismatch.second) {
  94             LogPrintf(" (2)");
  95         }
  96         LogPrintf(" %s\n", i.second.ToString());
  97     }
  98     assert(false);
  99 }
 100
 101 static void push_lock(void* c, const CLockLocation& locklocation)
 102 {
 103     if (lockstack.get() == nullptr)
 104         lockstack.reset(new LockStack);
 105
 106     boost::unique_lock<boost::mutex> lock(lockdata.dd_mutex);
 107
 108     (*lockstack).push_back(std::make_pair(c, locklocation));
 109
 110     for (const std::pair<void*, CLockLocation> & i : (*lockstack)) {
 111         if (i.first == c)
 112             break;
 113
 114         std::pair<void*, void*> p1 = std::make_pair(i.first, c);
 115         if (lockdata.lockorders.count(p1))
 116             continue;
 117         lockdata.lockorders[p1] = (*lockstack);
 118
 119         std::pair<void*, void*> p2 = std::make_pair(c, i.first);
 120         lockdata.invlockorders.insert(p2);
 121         if (lockdata.lockorders.count(p2))
 122             potential_deadlock_detected(p1, lockdata.lockorders[p2], lockdata.lockorders[p1]);
 123     }
 124 }
 125
 126 static void pop_lock()
 127 {
 128     (*lockstack).pop_back();
 129 }
 130
 131 void EnterCritical(const char* pszName, const char* pszFile, int nLine, void* cs, bool fTry)
 132 {
 133     push_lock(cs, CLockLocation(pszName, pszFile, nLine, fTry));
 134 }
 135
 136 void LeaveCritical()
 137 {
 138     pop_lock();
 139 }
 140
 141 std::string LocksHeld()
 142 {
 143     std::string result;
 144     for (const std::pair<void*, CLockLocation> & i : *lockstack)
 145         result += i.second.ToString() + std::string("\n");
 146     return result;
 147 }
 148
 149 void AssertLockHeldInternal(const char* pszName, const char* pszFile, int nLine, void* cs)
 150 {
 151     for (const std::pair<void*, CLockLocation> & i : *lockstack)
 152         if (i.first == cs)
 153             return;
 154     fprintf(stderr, "Assertion failed: lock %s not held in %s:%i; locks held:\n%s", pszName, pszFile, nLine, LocksHeld().c_str());
 155     abort();
 156 }
 157
 158 void DeleteLock(void* cs)
 159 {
 160     if (!lockdata.available) {
 161         // We're already shutting down.
 162         return;
 163     }
 164     boost::unique_lock<boost::mutex> lock(lockdata.dd_mutex);
 165     std::pair<void*, void*> item = std::make_pair(cs, nullptr);
 166     LockOrders::iterator it = lockdata.lockorders.lower_bound(item);
 167     while (it != lockdata.lockorders.end() && it->first.first == cs) {
 168         std::pair<void*, void*> invitem = std::make_pair(it->first.second, it->first.first);
 169         lockdata.invlockorders.erase(invitem);
 170         lockdata.lockorders.erase(it++);
 171     }
 172     InvLockOrders::iterator invit = lockdata.invlockorders.lower_bound(item);
 173     while (invit != lockdata.invlockorders.end() && invit->first == cs) {
 174         std::pair<void*, void*> invinvitem = std::make_pair(invit->second, invit->first);
 175         lockdata.lockorders.erase(invinvitem);
 176         lockdata.invlockorders.erase(invit++);
 177     }
 178 }
 179
 180 #endif /* DEBUG_LOCKORDER */