1 files changed, 215 insertions, 0 deletions
diff --git a/src/sync.cpp b/src/sync.cpp
new file mode 100644
index 000000000..257093fad
--- /dev/null
+++ b/src/sync.cpp
@@ -0,0 +1,215 @@
+// Copyright (c) 2011-2018 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#if defined(HAVE_CONFIG_H)
+#include <config/bitcoin-config.h>
+#endif
+
+#include <sync.h>
+#include <tinyformat.h>
+
+#include <logging.h>
+#include <util/strencodings.h>
+#include <util/threadnames.h>
+
+
+#include <map>
+#include <set>
+
+#ifdef DEBUG_LOCKCONTENTION
+#if !defined(HAVE_THREAD_LOCAL)
+static_assert(false, "thread_local is not supported");
+#endif
+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,
+        const std::string& thread_name)
+        : fTry(fTryIn),
+          mutexName(pszName),
+          sourceFile(pszFile),
+          m_thread_name(thread_name),
+          sourceLine(nLine) {}
+
+    std::string ToString() const
+    {
+        return strprintf(
+            "%s %s:%s%s (in thread %s)",
+            mutexName, sourceFile, itostr(sourceLine), (fTry ? " (TRY)" : ""), m_thread_name);
+    }
+
+private:
+    bool fTry;
+    std::string mutexName;
+    std::string sourceFile;
+    const std::string& m_thread_name;
+    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;
+    std::mutex dd_mutex;
+};
+LockData& GetLockData() {
+    static LockData lockdata;
+    return lockdata;
+}
+
+static thread_local LockStack g_lockstack;
+
+static void potential_deadlock_detected(const std::pair<void*, void*>& mismatch, const LockStack& s1, const LockStack& s2)
+{
+    LogPrintf("POTENTIAL DEADLOCK DETECTED\n");
+    LogPrintf("Previous lock order was:\n");
+    for (const std::pair<void*, CLockLocation> & i : s2) {
+        if (i.first == mismatch.first) {
+            LogPrintf(" (1)"); /* Continued */
+        }
+        if (i.first == mismatch.second) {
+            LogPrintf(" (2)"); /* Continued */
+        }
+        LogPrintf(" %s\n", i.second.ToString());
+    }
+    LogPrintf("Current lock order is:\n");
+    for (const std::pair<void*, CLockLocation> & i : s1) {
+        if (i.first == mismatch.first) {
+            LogPrintf(" (1)"); /* Continued */
+        }
+        if (i.first == mismatch.second) {
+            LogPrintf(" (2)"); /* Continued */
+        }
+        LogPrintf(" %s\n", i.second.ToString());
+    }
+    if (g_debug_lockorder_abort) {
+        tfm::format(std::cerr, "Assertion failed: detected inconsistent lock order at %s:%i, details in debug log.\n", __FILE__, __LINE__);
+        abort();
+    }
+    throw std::logic_error("potential deadlock detected");
+}
+
+static void push_lock(void* c, const CLockLocation& locklocation)
+{
+    LockData& lockdata = GetLockData();
+    std::lock_guard<std::mutex> lock(lockdata.dd_mutex);
+
+    g_lockstack.push_back(std::make_pair(c, locklocation));
+
+    for (const std::pair<void*, CLockLocation>& i : g_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.emplace(p1, g_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()
+{
+    g_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, util::ThreadGetInternalName()));
+}
+
+void LeaveCritical()
+{
+    pop_lock();
+}
+
+std::string LocksHeld()
+{
+    std::string result;
+    for (const std::pair<void*, CLockLocation>& i : g_lockstack)
+        result += i.second.ToString() + std::string("\n");
+    return result;
+}
+
+void AssertLockHeldInternal(const char* pszName, const char* pszFile, int nLine, void* cs)
+{
+    for (const std::pair<void*, CLockLocation>& i : g_lockstack)
+        if (i.first == cs)
+            return;
+    tfm::format(std::cerr, "Assertion failed: lock %s not held in %s:%i; locks held:\n%s", pszName, pszFile, nLine, LocksHeld());
+    abort();
+}
+
+void AssertLockNotHeldInternal(const char* pszName, const char* pszFile, int nLine, void* cs)
+{
+    for (const std::pair<void*, CLockLocation>& i : g_lockstack) {
+        if (i.first == cs) {
+            tfm::format(std::cerr, "Assertion failed: lock %s held in %s:%i; locks held:\n%s", pszName, pszFile, nLine, LocksHeld());
+            abort();
+        }
+    }
+}
+
+void DeleteLock(void* cs)
+{
+    LockData& lockdata = GetLockData();
+    if (!lockdata.available) {
+        // We're already shutting down.
+        return;
+    }
+    std::lock_guard<std::mutex> lock(lockdata.dd_mutex);
+    std::pair<void*, void*> item = std::make_pair(cs, nullptr);
+    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++);
+    }
+}
+
+bool g_debug_lockorder_abort = true;
+
+#endif /* DEBUG_LOCKORDER */