1 files changed, 176 insertions, 0 deletions
diff --git a/src/sync.cpp b/src/sync.cpp
new file mode 100644
index 000000000..1837e8d53
--- /dev/null
+++ b/src/sync.cpp
@@ -0,0 +1,176 @@
+// Copyright (c) 2011-2012 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;
+
+static boost::mutex dd_mutex;
+static std::map<std::pair<void*, void*>, LockStack> lockorders;
+static 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);
+
+    dd_mutex.lock();
+
+    (*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 (lockorders.count(p1))
+                continue;
+            lockorders[p1] = (*lockstack);
+
+            std::pair<void*, void*> p2 = std::make_pair(c, i.first);
+            if (lockorders.count(p2))
+                potential_deadlock_detected(p1, lockorders[p2], lockorders[p1]);
+        }
+    }
+    dd_mutex.unlock();
+}
+
+static void pop_lock()
+{
+    dd_mutex.lock();
+    (*lockstack).pop_back();
+    dd_mutex.unlock();
+}
+
+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();
+}
+
+#endif /* DEBUG_LOCKORDER */