1 files changed, 39 insertions, 0 deletions
diff --git a/src/sync.h b/src/sync.h
index 0cdbb59c70..204734c273 100644
--- a/src/sync.h
+++ b/src/sync.h
@@ -50,6 +50,7 @@ LEAVE_CRITICAL_SECTION(mutex); // no RAII
 #ifdef DEBUG_LOCKORDER
 void EnterCritical(const char* pszName, const char* pszFile, int nLine, void* cs, bool fTry = false);
 void LeaveCritical();
+void CheckLastCritical(void* cs, std::string& lockname, const char* guardname, const char* file, int line);
 std::string LocksHeld();
 void AssertLockHeldInternal(const char* pszName, const char* pszFile, int nLine, void* cs) ASSERT_EXCLUSIVE_LOCK(cs);
 void AssertLockNotHeldInternal(const char* pszName, const char* pszFile, int nLine, void* cs);
@@ -64,6 +65,7 @@ extern bool g_debug_lockorder_abort;
 #else
 void static inline EnterCritical(const char* pszName, const char* pszFile, int nLine, void* cs, bool fTry = false) {}
 void static inline LeaveCritical() {}
+void static inline CheckLastCritical(void* cs, std::string& lockname, const char* guardname, const char* file, int line) {}
 void static inline AssertLockHeldInternal(const char* pszName, const char* pszFile, int nLine, void* cs) ASSERT_EXCLUSIVE_LOCK(cs) {}
 void static inline AssertLockNotHeldInternal(const char* pszName, const char* pszFile, int nLine, void* cs) {}
 void static inline DeleteLock(void* cs) {}
@@ -171,8 +173,45 @@ public:
     {
         return Base::owns_lock();
     }
+
+protected:
+    // needed for reverse_lock
+    UniqueLock() { }
+
+public:
+    /**
+     * An RAII-style reverse lock. Unlocks on construction and locks on destruction.
+     */
+    class reverse_lock {
+    public:
+        explicit reverse_lock(UniqueLock& _lock, const char* _guardname, const char* _file, int _line) : lock(_lock), file(_file), line(_line) {
+            CheckLastCritical((void*)lock.mutex(), lockname, _guardname, _file, _line);
+            lock.unlock();
+            LeaveCritical();
+            lock.swap(templock);
+        }
+
+        ~reverse_lock() {
+            templock.swap(lock);
+            EnterCritical(lockname.c_str(), file.c_str(), line, (void*)lock.mutex());
+            lock.lock();
+        }
+
+     private:
+        reverse_lock(reverse_lock const&);
+        reverse_lock& operator=(reverse_lock const&);
+
+        UniqueLock& lock;
+        UniqueLock templock;
+        std::string lockname;
+        const std::string file;
+        const int line;
+     };
+     friend class reverse_lock;
 };
 
+#define REVERSE_LOCK(g) decltype(g)::reverse_lock PASTE2(revlock, __COUNTER__)(g, #g, __FILE__, __LINE__)
+
 template<typename MutexArg>
 using DebugLock = UniqueLock<typename std::remove_reference<typename std::remove_pointer<MutexArg>::type>::type>;