diff --git a/src/lib/homestore/heap_chunk_selector.cpp b/src/lib/homestore/heap_chunk_selector.cpp
index 6e2db4e1..75a5a020 100644
--- a/src/lib/homestore/heap_chunk_selector.cpp
+++ b/src/lib/homestore/heap_chunk_selector.cpp
@@ -49,6 +49,7 @@ csharedChunk HeapChunkSelector::select_chunk(homestore::blk_count_t count, const
     it->second->first.lock();
     if(it->second->second.empty()) {
         LOGINFO("No more available chunks found for pdev {}", pdevID);
+        it->second->first.unlock();
         return nullptr;
     }
     
diff --git a/src/lib/homestore/heap_chunk_selector.h b/src/lib/homestore/heap_chunk_selector.h
index ebe55627..861fdf82 100644
--- a/src/lib/homestore/heap_chunk_selector.h
+++ b/src/lib/homestore/heap_chunk_selector.h
@@ -44,7 +44,9 @@ class HeapChunkSelector : public homestore::ChunkSelector {
     csharedChunk select_chunk([[maybe_unused]]homestore::blk_count_t nblks, const homestore::blk_alloc_hints& hints);
 
 private:
+    //this holds all the chunks for each pdev, they are all unselected.
     folly::ConcurrentHashMap< uint32_t, std::shared_ptr< std::pair< std::mutex, VChunkHeap > > > m_pdev_heap_map;
+
     //for now, uint32_t is enough for the sum of all the available blocks of a pdev.
     //if necessary , we can change this to uint64_t to hold a larger sum.
     std::unordered_map< uint32_t, uint32_t> m_pdev_avalable_blk_map;
@@ -52,6 +54,5 @@ class HeapChunkSelector : public homestore::ChunkSelector {
     //hold all the chunks , selected or not
     std::unordered_set< VChunk > m_chunks;
     std::mutex lock;
-    
 };
 } // namespace homeobject
\ No newline at end of file