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/foreach.hpp>
  13 #include <boost/thread.hpp>
  14
  15 #ifdef DEBUG_LOCKCONTENTION
  16 void PrintLockContention(const char* pszName, const char* pszFile, int nLine)
  17 {
  18     LogPrintf("LOCKCONTENTION: %s\n", pszName);
  19     LogPrintf("Locker: %s:%d\n", pszFile, nLine);
  20 }
  21 #endif /* DEBUG_LOCKCONTENTION */
  22
  23 #ifdef DEBUG_LOCKORDER
  24 //
  25 // Early deadlock detection.
  26 // Problem being solved:
  27 //    Thread 1 locks  A, then B, then C
  28 //    Thread 2 locks  D, then C, then A
  29 //     --> may result in deadlock between the two threads, depending on when they run.
  30 // Solution implemented here:
  31 // Keep track of pairs of locks: (A before B), (A before C), etc.
  32 // Complain if any thread tries to lock in a different order.
  33 //
  34
  35 struct CLockLocation {
  36     CLockLocation(const char* pszName, const char* pszFile, int nLine, bool fTryIn)
  37     {
  38         mutexName = pszName;
  39         sourceFile = pszFile;
  40         sourceLine = nLine;
  41         fTry = fTryIn;
  42     }
  43
  44     std::string ToString() const
  45     {
  46         return mutexName + "  " + sourceFile + ":" + itostr(sourceLine) + (fTry ? " (TRY)" : "");
  47     }
  48
  49     bool fTry;
  50 private:
  51     std::string mutexName;
  52     std::string sourceFile;
  53     int sourceLine;
  54 };
  55
  56 typedef std::vector<std::pair<void*, CLockLocation> > LockStack;
  57 typedef std::map<std::pair<void*, void*>, LockStack> LockOrders;
  58 typedef std::set<std::pair<void*, void*> > InvLockOrders;
  59
  60 struct LockData {
  61     // Very ugly hack: as the global constructs and destructors run single
  62     // threaded, we use this boolean to know whether LockData still exists,
  63     // as DeleteLock can get called by global CCriticalSection destructors
  64     // after LockData disappears.
  65     bool available;
  66     LockData() : available(true) {}
  67     ~LockData() { available = false; }
  68
  69     LockOrders lockorders;
  70     InvLockOrders invlockorders;
  71     boost::mutex dd_mutex;
  72 } static lockdata;
  73
  74 boost::thread_specific_ptr<LockStack> lockstack;
  75
  76 static void potential_deadlock_detected(const std::pair<void*, void*>& mismatch, const LockStack& s1, const LockStack& s2)
  77 {
  78     LogPrintf("POTENTIAL DEADLOCK DETECTED\n");
  79     LogPrintf("Previous lock order was:\n");
  80     for (const std::pair<void*, CLockLocation> & i : s2) {
  81         if (i.first == mismatch.first) {
  82             LogPrintf(" (1)");
  83         }
  84         if (i.first == mismatch.second) {
  85             LogPrintf(" (2)");
  86         }
  87         LogPrintf(" %s\n", i.second.ToString());
  88     }
  89     LogPrintf("Current lock order is:\n");
  90     for (const std::pair<void*, CLockLocation> & i : s1) {
  91         if (i.first == mismatch.first) {
  92             LogPrintf(" (1)");
  93         }
  94         if (i.first == mismatch.second) {
  95             LogPrintf(" (2)");
  96         }
  97         LogPrintf(" %s\n", i.second.ToString());
  98     }
  99     assert(false);
 100 }
 101
 102 static void push_lock(void* c, const CLockLocation& locklocation, bool fTry)
 103 {
 104     if (lockstack.get() == NULL)
 105         lockstack.reset(new LockStack);
 106
 107     boost::unique_lock<boost::mutex> lock(lockdata.dd_mutex);
 108
 109     (*lockstack).push_back(std::make_pair(c, locklocation));
 110
 111     for (const std::pair<void*, CLockLocation> & i : (*lockstack)) {
 112         if (i.first == c)
 113             break;
 114
 115         std::pair<void*, void*> p1 = std::make_pair(i.first, c);
 116         if (lockdata.lockorders.count(p1))
 117             continue;
 118         lockdata.lockorders[p1] = (*lockstack);
 119
 120         std::pair<void*, void*> p2 = std::make_pair(c, i.first);
 121         lockdata.invlockorders.insert(p2);
 122         if (lockdata.lockorders.count(p2))
 123             potential_deadlock_detected(p1, lockdata.lockorders[p2], lockdata.lockorders[p1]);
 124     }
 125 }
 126
 127 static void pop_lock()
 128 {
 129     (*lockstack).pop_back();
 130 }
 131
 132 void EnterCritical(const char* pszName, const char* pszFile, int nLine, void* cs, bool fTry)
 133 {
 134     push_lock(cs, CLockLocation(pszName, pszFile, nLine, fTry), fTry);
 135 }
 136
 137 void LeaveCritical()
 138 {
 139     pop_lock();
 140 }
 141
 142 std::string LocksHeld()
 143 {
 144     std::string result;
 145     for (const std::pair<void*, CLockLocation> & i : *lockstack)
 146         result += i.second.ToString() + std::string("\n");
 147     return result;
 148 }
 149
 150 void AssertLockHeldInternal(const char* pszName, const char* pszFile, int nLine, void* cs)
 151 {
 152     for (const std::pair<void*, CLockLocation> & i : *lockstack)
 153         if (i.first == cs)
 154             return;
 155     fprintf(stderr, "Assertion failed: lock %s not held in %s:%i; locks held:\n%s", pszName, pszFile, nLine, LocksHeld().c_str());
 156     abort();
 157 }
 158
 159 void DeleteLock(void* cs)
 160 {
 161     if (!lockdata.available) {
 162         // We're already shutting down.
 163         return;
 164     }
 165     boost::unique_lock<boost::mutex> lock(lockdata.dd_mutex);
 166     std::pair<void*, void*> item = std::make_pair(cs, (void*)0);
 167     LockOrders::iterator it = lockdata.lockorders.lower_bound(item);
 168     while (it != lockdata.lockorders.end() && it->first.first == cs) {
 169         std::pair<void*, void*> invitem = std::make_pair(it->first.second, it->first.first);
 170         lockdata.invlockorders.erase(invitem);
 171         lockdata.lockorders.erase(it++);
 172     }
 173     InvLockOrders::iterator invit = lockdata.invlockorders.lower_bound(item);
 174     while (invit != lockdata.invlockorders.end() && invit->first == cs) {
 175         std::pair<void*, void*> invinvitem = std::make_pair(invit->second, invit->first);
 176         lockdata.lockorders.erase(invinvitem);
 177         lockdata.invlockorders.erase(invit++);
 178     }
 179 }
 180
 181 #endif /* DEBUG_LOCKORDER */