Compile with DEBUG_LOCKORDER to detect inconsistent lock orderings that can cause deadlocks

src/net.h

@@ -677,7 +677,7 @@ public:
 
     void BeginMessage(const char* pszCommand)
     {
-        cs_vSend.Enter();
+        cs_vSend.Enter("cs_vSend", __FILE__, __LINE__);
         if (nHeaderStart != -1)
             AbortMessage();
         nHeaderStart = vSend.size();

src/util.cpp

@@ -909,4 +909,122 @@ string FormatFullVersion()
 
 
 
+#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 trys to lock in a different order.
+//
+
+struct CLockLocation
+{
+    std::string mutexName;
+    std::string sourceFile;
+    int sourceLine;
+
+    CLockLocation(const char* pszName, const char* pszFile, int nLine)
+    {
+        mutexName = pszName;
+        sourceFile = pszFile;
+        sourceLine = nLine;
+    }
+};
+
+typedef std::vector< std::pair<CCriticalSection*, CLockLocation> > LockStack;
+
+static boost::interprocess::interprocess_mutex dd_mutex;
+static std::map<std::pair<CCriticalSection*, CCriticalSection*>, LockStack> lockorders;
+static boost::thread_specific_ptr<LockStack> lockstack;
+
+
+static void potential_deadlock_detected(const LockStack& s1, const LockStack& s2)
+{
+    printf("POTENTIAL DEADLOCK DETECTED\n");
+    printf("Previous lock order was:\n");
+    BOOST_FOREACH(const PAIRTYPE(CCriticalSection*, CLockLocation)& i, s2)
+    {
+        printf(" %s  %s:%d\n", i.second.mutexName.c_str(), i.second.sourceFile.c_str(), i.second.sourceLine);
+    }
+    printf("Current lock order is:\n");
+    BOOST_FOREACH(const PAIRTYPE(CCriticalSection*, CLockLocation)& i, s1)
+    {
+        printf(" %s  %s:%d\n", i.second.mutexName.c_str(), i.second.sourceFile.c_str(), i.second.sourceLine);
+    }
+}
+
+static void push_lock(CCriticalSection* c, const CLockLocation& locklocation)
+{
+    bool fOrderOK = true;
+    if (lockstack.get() == NULL)
+        lockstack.reset(new LockStack);
+
+    dd_mutex.lock();
+
+    (*lockstack).push_back(std::make_pair(c, locklocation));
+
+    BOOST_FOREACH(const PAIRTYPE(CCriticalSection*, CLockLocation)& i, (*lockstack))
+    {
+        if (i.first == c) break;
+
+        std::pair<CCriticalSection*, CCriticalSection*> p1 = std::make_pair(i.first, c);
+        if (lockorders.count(p1))
+            continue;
+        lockorders[p1] = (*lockstack);
+
+        std::pair<CCriticalSection*, CCriticalSection*> p2 = std::make_pair(c, i.first);
+        if (lockorders.count(p2))
+        {
+            potential_deadlock_detected(lockorders[p2], lockorders[p1]);
+            break;
+        }
+    }
+    dd_mutex.unlock();
+}
+
+static void pop_lock()
+{
+    (*lockstack).pop_back();
+}
+
+void CCriticalSection::Enter(const char* pszName, const char* pszFile, int nLine)
+{
+    push_lock(this, CLockLocation(pszName, pszFile, nLine));
+    mutex.lock();
+}
+void CCriticalSection::Leave()
+{
+    mutex.unlock();
+    pop_lock();
+}
+bool CCriticalSection::TryEnter(const char* pszName, const char* pszFile, int nLine)
+{
+    push_lock(this, CLockLocation(pszName, pszFile, nLine));
+    bool result = mutex.try_lock();
+    if (!result) pop_lock();
+    return result;
+}
+
+#else
+
+void CCriticalSection::Enter(const char*, const char*, int)
+{
+    mutex.lock();
+}
+
+void CCriticalSection::Leave()
+{
+    mutex.unlock();
+}
+
+bool CCriticalSection::TryEnter(const char*, const char*, int)
+{
+    bool result = mutex.try_lock();
+    return result;
+}
 
+#endif /* DEBUG_LOCKORDER */

src/util.h

@@ -223,31 +223,17 @@ std::string FormatFullVersion();
 
 
 
-// Wrapper to automatically initialize critical sections
+// Wrapper to automatically initialize mutex
 class CCriticalSection
 {
-#ifdef __WXMSW__
-protected:
-    CRITICAL_SECTION cs;
-public:
-    explicit CCriticalSection() { InitializeCriticalSection(&cs); }
-    ~CCriticalSection() { DeleteCriticalSection(&cs); }
-    void Enter() { EnterCriticalSection(&cs); }
-    void Leave() { LeaveCriticalSection(&cs); }
-    bool TryEnter() { return TryEnterCriticalSection(&cs); }
-#else
 protected:
     boost::interprocess::interprocess_recursive_mutex mutex;
 public:
     explicit CCriticalSection() { }
     ~CCriticalSection() { }
-    void Enter() { mutex.lock(); }
-    void Leave() { mutex.unlock(); }
-    bool TryEnter() { return mutex.try_lock(); }
-#endif
-public:
-    const char* pszFile;
-    int nLine;
+    void Enter(const char* pszName, const char* pszFile, int nLine);
+    void Leave();
+    bool TryEnter(const char* pszName, const char* pszFile, int nLine);
 };
 
 // Automatically leave critical section when leaving block, needed for exception safety
@@ -255,9 +241,17 @@ class CCriticalBlock
 {
 protected:
     CCriticalSection* pcs;
+
 public:
-    CCriticalBlock(CCriticalSection& csIn) { pcs = &csIn; pcs->Enter(); }
-    ~CCriticalBlock() { pcs->Leave(); }
+    CCriticalBlock(CCriticalSection& csIn, const char* pszName, const char* pszFile, int nLine)
+    {
+        pcs = &csIn;
+        pcs->Enter(pszName, pszFile, nLine);
+    }
+    ~CCriticalBlock()
+    {
+        pcs->Leave();
+    }
 };
 
 // WARNING: This will catch continue and break!
@@ -265,22 +259,32 @@ public:
 // I'd rather be careful than suffer the other more error prone syntax.
 // The compiler will optimise away all this loop junk.
 #define CRITICAL_BLOCK(cs)     \
-    for (bool fcriticalblockonce=true; fcriticalblockonce; assert("break caught by CRITICAL_BLOCK!" && !fcriticalblockonce), fcriticalblockonce=false)  \
-    for (CCriticalBlock criticalblock(cs); fcriticalblockonce && (cs.pszFile=__FILE__, cs.nLine=__LINE__, true); fcriticalblockonce=false, cs.pszFile=NULL, cs.nLine=0)
+    for (bool fcriticalblockonce=true; fcriticalblockonce; assert(("break caught by CRITICAL_BLOCK!" && !fcriticalblockonce)), fcriticalblockonce=false) \
+        for (CCriticalBlock criticalblock(cs, #cs, __FILE__, __LINE__); fcriticalblockonce; fcriticalblockonce=false)
 
 class CTryCriticalBlock
 {
 protected:
     CCriticalSection* pcs;
+
 public:
-    CTryCriticalBlock(CCriticalSection& csIn) { pcs = (csIn.TryEnter() ? &csIn : NULL); }
-    ~CTryCriticalBlock() { if (pcs) pcs->Leave(); }
+    CTryCriticalBlock(CCriticalSection& csIn, const char* pszName, const char* pszFile, int nLine)
+    {
+        pcs = (csIn.TryEnter(pszName, pszFile, nLine) ? &csIn : NULL);
+    }
+    ~CTryCriticalBlock()
+    {
+        if (pcs)
+        {
+            pcs->Leave();
+        }
+    }
     bool Entered() { return pcs != NULL; }
 };
 
 #define TRY_CRITICAL_BLOCK(cs)     \
-    for (bool fcriticalblockonce=true; fcriticalblockonce; assert("break caught by TRY_CRITICAL_BLOCK!" && !fcriticalblockonce), fcriticalblockonce=false)  \
-    for (CTryCriticalBlock criticalblock(cs); fcriticalblockonce && (fcriticalblockonce = criticalblock.Entered()) && (cs.pszFile=__FILE__, cs.nLine=__LINE__, true); fcriticalblockonce=false, cs.pszFile=NULL, cs.nLine=0)
+    for (bool fcriticalblockonce=true; fcriticalblockonce; assert(("break caught by TRY_CRITICAL_BLOCK!" && !fcriticalblockonce)), fcriticalblockonce=false) \
+        for (CTryCriticalBlock criticalblock(cs, #cs, __FILE__, __LINE__); fcriticalblockonce && (fcriticalblockonce = criticalblock.Entered()); fcriticalblockonce=false)