Make atomic value updates/reads if required. This is needed for struc…

…ts bigger than processor word size.
koculu · Jul 6, 2022 · daa0131 · daa0131
1 parent 6ffd7ae
commit daa0131
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Showing 3 changed files with 46 additions and 11 deletions.
diff --git a/src/ZoneTree/Collections/SkipList.cs b/src/ZoneTree/Collections/SkipList.cs
@@ -1,4 +1,5 @@
-using Tenray.Collections;
+using System.Runtime.CompilerServices;
+using Tenray.Collections;
 
 namespace ZoneTree.Collections;
 
@@ -300,9 +301,46 @@ public bool Remove(in TKey key)
 
     public class SkipListNode
     {
+        /// <summary>
+        /// A conforming CLI shall guarantee that read and write access 
+        /// to properly aligned memory locations no larger than the native word size
+        /// (the size of type native int) is atomic.
+        /// </summary>
+        private static bool IsValueAssignmentAtomic =
+            Unsafe.SizeOf<TValue>() <= IntPtr.Size;
+
         public SkipListNode[] Next;
+
         public TKey Key;
-        public TValue Value;
+
+        private TValue _value;
+
+        public TValue Value {
+            get
+            {
+                if (IsValueAssignmentAtomic)
+                    return _value;
+                else
+                {
+                    lock(this)
+                    {
+                        return _value;
+                    }
+                }
+            }
+            set
+            {
+                if(IsValueAssignmentAtomic)
+                    _value = value;
+                else
+                {
+                    lock(this)
+                    {
+                        _value = value;
+                    }
+                }
+            }
+        }
         public readonly int Level;
         public volatile bool isInserted;
         public SkipListNode NextNode => Next[0];
@@ -344,10 +382,5 @@ public void MarkInserted()
         {
             isInserted = true;
         }
-
-        public ref TValue GetValueRef()
-        {
-            return ref Value;
-        }
     }
 }
diff --git a/src/ZoneTree/Directory.Build.props b/src/ZoneTree/Directory.Build.props
@@ -5,8 +5,8 @@
     <Authors>Ahmed Yasin Koculu</Authors>
     <PackageId>Topaz</PackageId>
     <Title>Topaz</Title>
-    <ProductVersion>1.0.0.0</ProductVersion>
-    <Version>1.0.0.0</Version>
+    <ProductVersion>1.0.1.0</ProductVersion>
+    <Version>1.0.1.0</Version>
     <Authors>Ahmed Yasin Koculu</Authors>
     <AssemblyTitle>ZoneTree</AssemblyTitle>
     <Description>ZoneTree is a persistent, high-performance key-value database for .NET. It can operate in memory or on disk. (Optimized for SSDs)</Description>

diff --git a/src/ZoneTree/Segments/MutableSegment.cs b/src/ZoneTree/Segments/MutableSegment.cs
@@ -141,15 +141,17 @@ public AddOrUpdateResult Delete(TKey key)
             var status = SkipList.AddOrUpdate(key,
                 (x) =>
                 {
-                    ref var value = ref x.GetValueRef();
+                    var value = x.Value;
                     MarkValueDeleted(ref value);
+                    x.Value = value;
                     WriteAheadLog.Append(in key, in value);
                     return AddOrUpdateResult.ADDED;
                 },
                 (x) =>
                 {
-                    ref var value = ref x.GetValueRef();
+                    var value = x.Value;
                     MarkValueDeleted(ref value);
+                    x.Value = value;
                     WriteAheadLog.Append(in key, in value);
                     return AddOrUpdateResult.UPDATED;
                 });