#1545 state locking

skalenetwork · Jun 21, 2024 · d1aee99 · d1aee99
1 parent 71de8a5
commit d1aee99
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Showing 3 changed files with 25 additions and 12 deletions.
diff --git a/libdevcore/LevelDB.cpp b/libdevcore/LevelDB.cpp
@@ -172,15 +172,18 @@ std::string LevelDB::lookup( Slice _key, const std::shared_ptr<LevelDBSnap>& _sn
 
         auto readOptions = m_readOptions;
 
-        std::unique_ptr<std::shared_lock<std::shared_mutex>> snapshotUseLock;
         if (_snap) {
+
+            // read from snap
             readOptions.snapshot = _snap->getSnapHandle();
-            // create as shared lock on snap use mutex that will be unlocked on function exit
-            // this make sure snap is not concurrently closed while used
-            snapshotUseLock = _snap->lockToPreventConcurrentClose();
+            // this make sure snap is not concurrently closed while used in Get()
+            auto snapshotUseLock = _snap->lockToPreventConcurrentClose();
+            LDB_CHECK(!_snap->isClosed())
+            status = m_db->Get( readOptions, key, &value );
+        } else {
+            // read from live DB
+            status = m_db->Get( readOptions, key, &value );
         }
-
-        status = m_db->Get( readOptions, key, &value );
     }
     if ( status.IsNotFound() )
         return std::string();
@@ -203,15 +206,17 @@ bool LevelDB::exists( Slice _key, const std::shared_ptr<LevelDBSnap>& _snap  ) c
         SharedDBGuard lock( *this );
         auto readOptions = m_readOptions;
 
-        std::unique_ptr<std::shared_lock<std::shared_mutex>> snapshotClosePreventionLock;
         if (_snap) {
+            // read from snap
             readOptions.snapshot = _snap->getSnapHandle();
-            // create as shared lock on snap close mutex that will be unlocked on function exit
-            // this make sure snap is not concurrently closed while used
-            snapshotClosePreventionLock = _snap->lockToPreventConcurrentClose();
+            // this make sure snap is not concurrently closed while used in Get()
+            auto snapshotUseLock = _snap->lockToPreventConcurrentClose();
+            status = m_db->Get( readOptions, key, &value );
+        } else {
+            // read from live DB
+            status = m_db->Get( readOptions, key, &value );
         }
 
-        status = m_db->Get( readOptions, key, &value );
     }
     if ( status.IsNotFound() )
         return false;

diff --git a/libdevcore/LevelDBSnap.cpp b/libdevcore/LevelDBSnap.cpp
@@ -23,13 +23,18 @@
 #include "LevelDB.h"
 
 const leveldb::Snapshot* dev::db::LevelDBSnap::getSnapHandle() const {
+    LDB_CHECK(!m_isClosed)
     return m_snap;
 }
 
 using std::string, std::runtime_error;
 
 namespace dev::db {
 
+bool LevelDBSnap::isClosed() const {
+    return m_isClosed;
+}
+
 
 LevelDBSnap::LevelDBSnap(
     uint64_t _blockId, const leveldb::Snapshot* _snap, uint64_t _parentLevelDBIdentifier )
@@ -92,7 +97,9 @@ uint64_t LevelDBSnap::getCreationTimeMs() const {
     return m_creationTimeMs;
 }
 std::unique_ptr<std::shared_lock<std::shared_mutex>> LevelDBSnap::lockToPreventConcurrentClose()  {
-    return std::make_unique<std::shared_lock<std::shared_mutex>>( m_usageMutex );
+    // we are trying to use the snap, so it should not be closed
+    LDB_CHECK(!m_isClosed);
+    auto result =  std::make_unique<std::shared_lock<std::shared_mutex>>( m_usageMutex );
 }
 
 

diff --git a/libdevcore/LevelDBSnap.h b/libdevcore/LevelDBSnap.h
@@ -55,6 +55,7 @@ class LevelDBSnap {
     uint64_t getObjectId() const;
 
     const leveldb::Snapshot* getSnapHandle() const;
+    bool isClosed() const;
 
 private: