Merge tag 'branch-0.13' into bugfix_gitdir

1 files changed, 84 insertions, 27 deletions

diff --git a/src/sync.cpp b/src/sync.cpp
index ef35c9d64..641ed2c8c 100644
--- a/src/sync.cpp
+++ b/src/sync.cpp
@@ -1,5 +1,5 @@
-// Copyright (c) 2011-2012 The Bitcoin developers
-// Distributed under the MIT/X11 software license, see the accompanying
+// Copyright (c) 2011-2015 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"
@@ -33,20 +33,22 @@ void PrintLockContention(const char* pszName, const char* pszFile, int nLine)
 //
 
 struct CLockLocation {
-    CLockLocation(const char* pszName, const char* pszFile, int nLine)
+    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);
+        return mutexName + "  " + sourceFile + ":" + itostr(sourceLine) + (fTry ? " (TRY)" : "");
     }
 
     std::string MutexName() const { return mutexName; }
 
+    bool fTry;
 private:
     std::string mutexName;
     std::string sourceFile;
@@ -54,31 +56,73 @@ private:
 };
 
 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;
 
-static boost::mutex dd_mutex;
-static std::map<std::pair<void*, void*>, LockStack> lockorders;
-static boost::thread_specific_ptr<LockStack> lockstack;
+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;
+    boost::mutex dd_mutex;
+} static lockdata;
+
+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)
+        if (i.first == mismatch.first) {
             LogPrintf(" (1)");
-        if (i.first == mismatch.second)
+            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)
+        if (i.first == mismatch.first) {
             LogPrintf(" (1)");
-        if (i.first == mismatch.second)
+            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)
@@ -86,8 +130,7 @@ static void push_lock(void* c, const CLockLocation& locklocation, bool fTry)
     if (lockstack.get() == NULL)
         lockstack.reset(new LockStack);
 
-    LogPrint("lock", "Locking: %s\n", locklocation.ToString());
-    dd_mutex.lock();
+    boost::unique_lock<boost::mutex> lock(lockdata.dd_mutex);
 
     (*lockstack).push_back(std::make_pair(c, locklocation));
 
@@ -97,34 +140,26 @@ static void push_lock(void* c, const CLockLocation& locklocation, bool fTry)
                 break;
 
             std::pair<void*, void*> p1 = std::make_pair(i.first, c);
-            if (lockorders.count(p1))
+            if (lockdata.lockorders.count(p1))
                 continue;
-            lockorders[p1] = (*lockstack);
+            lockdata.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]);
-                break;
-            }
+            lockdata.invlockorders.insert(p2);
+            if (lockdata.lockorders.count(p2))
+                potential_deadlock_detected(p1, lockdata.lockorders[p2], lockdata.lockorders[p1]);
         }
     }
-    dd_mutex.unlock();
 }
 
 static void pop_lock()
 {
-    if (fDebug) {
-        const CLockLocation& locklocation = (*lockstack).rbegin()->second;
-        LogPrint("lock", "Unlocked: %s\n", locklocation.ToString());
-    }
-    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);
+    push_lock(cs, CLockLocation(pszName, pszFile, nLine, fTry), fTry);
 }
 
 void LeaveCritical()
@@ -149,4 +184,26 @@ void AssertLockHeldInternal(const char* pszName, const char* pszFile, int nLine,
     abort();
 }
 
+void DeleteLock(void* cs)
+{
+    if (!lockdata.available) {
+        // We're already shutting down.
+        return;
+    }
+    boost::unique_lock<boost::mutex> lock(lockdata.dd_mutex);
+    std::pair<void*, void*> item = std::make_pair(cs, (void*)0);
+    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++);
+    }
+}
+
 #endif /* DEBUG_LOCKORDER */