Merge #19340: Preserve the LockData initial state if "potential deadlock detected" exception thrown

63e9e40 test: Add LockStackEmpty() (Hennadii Stepanov)
42b2a95 test: Repeat deadlock tests (Hennadii Stepanov)
1f96be2 Preserve initial state if push_lock() throws exception (Hennadii Stepanov)

Pull request description:

  On master (e3fa3c7) if the `push_lock()` throws the "potential deadlock detected" exception (via the `potential_deadlock_detected()` call), the `LockData` instance internal state differs from one when the `push_lock()` was called. This non-well behaviour makes (at least) testing brittle.

  This PR preserves the `LockData` instance initial state if `push_lock()` throws an exception, and improves the `sync_tests` unit test.

ACKs for top commit:
  MarcoFalke:
    re-ACK 63e9e40
  vasild:
    ACK 63e9e40

Tree-SHA512: 7679182154ce5f079b44b790faf76eb5f553328dea70a326ff6b600db70e2f9ae015a33a104ca070cb660318280cb79b6b42e37ea5166f26f9e627ba721fcdec

Author: MarcoFalke

src/sync.cpp

@@ -149,12 +149,17 @@ static void push_lock(void* c, const CLockLocation& locklocation)
         const LockPair p1 = std::make_pair(i.first, c);
         if (lockdata.lockorders.count(p1))
             continue;
-        lockdata.lockorders.emplace(p1, lock_stack);
 
         const LockPair p2 = std::make_pair(c, i.first);
+        if (lockdata.lockorders.count(p2)) {
+            auto lock_stack_copy = lock_stack;
+            lock_stack.pop_back();
+            potential_deadlock_detected(p1, lockdata.lockorders[p2], lock_stack_copy);
+            // potential_deadlock_detected() does not return.
+        }
+
+        lockdata.lockorders.emplace(p1, lock_stack);
         lockdata.invlockorders.insert(p2);
-        if (lockdata.lockorders.count(p2))
-            potential_deadlock_detected(p1, lockdata.lockorders[p2], lockdata.lockorders[p1]);
     }
 }
 
@@ -259,6 +264,17 @@ void DeleteLock(void* cs)
     }
 }
 
+bool LockStackEmpty()
+{
+    LockData& lockdata = GetLockData();
+    std::lock_guard<std::mutex> lock(lockdata.dd_mutex);
+    const auto it = lockdata.m_lock_stacks.find(std::this_thread::get_id());
+    if (it == lockdata.m_lock_stacks.end()) {
+        return true;
+    }
+    return it->second.empty();
+}
+
 bool g_debug_lockorder_abort = true;
 
 #endif /* DEBUG_LOCKORDER */

src/sync.h

@@ -56,6 +56,7 @@ template <typename MutexType>
 void AssertLockHeldInternal(const char* pszName, const char* pszFile, int nLine, MutexType* cs) ASSERT_EXCLUSIVE_LOCK(cs);
 void AssertLockNotHeldInternal(const char* pszName, const char* pszFile, int nLine, void* cs);
 void DeleteLock(void* cs);
+bool LockStackEmpty();
 
 /**
  * Call abort() if a potential lock order deadlock bug is detected, instead of
@@ -64,13 +65,14 @@ void DeleteLock(void* cs);
  */
 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) {}
+inline void EnterCritical(const char* pszName, const char* pszFile, int nLine, void* cs, bool fTry = false) {}
+inline void LeaveCritical() {}
+inline void CheckLastCritical(void* cs, std::string& lockname, const char* guardname, const char* file, int line) {}
 template <typename MutexType>
-void static inline AssertLockHeldInternal(const char* pszName, const char* pszFile, int nLine, MutexType* 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) {}
+inline void AssertLockHeldInternal(const char* pszName, const char* pszFile, int nLine, MutexType* cs) ASSERT_EXCLUSIVE_LOCK(cs) {}
+inline void AssertLockNotHeldInternal(const char* pszName, const char* pszFile, int nLine, void* cs) {}
+inline void DeleteLock(void* cs) {}
+inline bool LockStackEmpty() { return true; }
 #endif
 #define AssertLockHeld(cs) AssertLockHeldInternal(#cs, __FILE__, __LINE__, &cs)
 #define AssertLockNotHeld(cs) AssertLockNotHeldInternal(#cs, __FILE__, __LINE__, &cs)

src/test/sync_tests.cpp

@@ -14,13 +14,15 @@ void TestPotentialDeadLockDetected(MutexType& mutex1, MutexType& mutex2)
     {
         LOCK2(mutex1, mutex2);
     }
+    BOOST_CHECK(LockStackEmpty());
     bool error_thrown = false;
     try {
         LOCK2(mutex2, mutex1);
     } catch (const std::logic_error& e) {
         BOOST_CHECK_EQUAL(e.what(), "potential deadlock detected: mutex1 -> mutex2 -> mutex1");
         error_thrown = true;
     }
+    BOOST_CHECK(LockStackEmpty());
     #ifdef DEBUG_LOCKORDER
     BOOST_CHECK(error_thrown);
     #else
@@ -40,9 +42,13 @@ BOOST_AUTO_TEST_CASE(potential_deadlock_detected)
 
     RecursiveMutex rmutex1, rmutex2;
     TestPotentialDeadLockDetected(rmutex1, rmutex2);
+    // The second test ensures that lock tracking data have not been broken by exception.
+    TestPotentialDeadLockDetected(rmutex1, rmutex2);
 
     Mutex mutex1, mutex2;
     TestPotentialDeadLockDetected(mutex1, mutex2);
+    // The second test ensures that lock tracking data have not been broken by exception.
+    TestPotentialDeadLockDetected(mutex1, mutex2);
 
     #ifdef DEBUG_LOCKORDER
     g_debug_lockorder_abort = prev;