Use -1 to report success and allow using element #1 in the SyncTable

VSadov · Dec 15, 2022 · 43a354d · 43a354d
1 parent 367acbb
commit 43a354d
Show file tree

Hide file tree

Showing 4 changed files with 17 additions and 17 deletions.
diff --git a/.../System.Private.CoreLib/src/Internal/Runtime/CompilerHelpers/SynchronizedMethodHelpers.cs b/.../System.Private.CoreLib/src/Internal/Runtime/CompilerHelpers/SynchronizedMethodHelpers.cs
@@ -15,7 +15,7 @@ private static void MonitorEnter(object obj, ref bool lockTaken)
         {
             // Inlined Monitor.Enter with a few tweaks
             int resultOrIndex = ObjectHeader.Acquire(obj);
-            if (resultOrIndex == 1)
+            if (resultOrIndex < 0)
             {
                 lockTaken = true;
                 return;
@@ -49,7 +49,7 @@ private static void MonitorEnterStatic(IntPtr pEEType, ref bool lockTaken)
             // Inlined Monitor.Enter with a few tweaks
             object obj = GetStaticLockObject(pEEType);
             int resultOrIndex = ObjectHeader.Acquire(obj);
-            if (resultOrIndex == 1)
+            if (resultOrIndex < 0)
             {
                 lockTaken = true;
                 return;

diff --git a/src/coreclr/nativeaot/System.Private.CoreLib/src/System/Threading/Monitor.NativeAot.cs b/src/coreclr/nativeaot/System.Private.CoreLib/src/System/Threading/Monitor.NativeAot.cs
@@ -42,7 +42,7 @@ private static Condition GetCondition(object obj)
         public static void Enter(object obj)
         {
             int resultOrIndex = ObjectHeader.Acquire(obj);
-            if (resultOrIndex == 1)
+            if (resultOrIndex < 0)
                 return;
 
             Lock lck = resultOrIndex == 0 ?
@@ -70,7 +70,7 @@ public static void Enter(object obj, ref bool lockTaken)
         public static bool TryEnter(object obj)
         {
             int resultOrIndex = ObjectHeader.TryAcquire(obj);
-            if (resultOrIndex == 1)
+            if (resultOrIndex < 0)
                 return true;
 
             if (resultOrIndex == 0)
@@ -97,7 +97,7 @@ public static bool TryEnter(object obj, int millisecondsTimeout)
                 throw new ArgumentOutOfRangeException(nameof(millisecondsTimeout), SR.ArgumentOutOfRange_NeedNonNegOrNegative1);
 
             int resultOrIndex = ObjectHeader.TryAcquire(obj);
-            if (resultOrIndex == 1)
+            if (resultOrIndex < 0)
                 return true;
 
             Lock lck = resultOrIndex == 0 ?

diff --git a/src/coreclr/nativeaot/System.Private.CoreLib/src/System/Threading/ObjectHeader.cs b/src/coreclr/nativeaot/System.Private.CoreLib/src/System/Threading/ObjectHeader.cs
@@ -248,16 +248,16 @@ public static unsafe void SetSyncEntryIndex(int* pHeader, int syncIndex)
         //
 
         // Returs:
-        //   1 - success
-        //   0 - failed
-        //   syncIndex - retry with the Lock
+        // -1 - success
+        // 0 - failed
+        // syncIndex - retry with the Lock
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static unsafe int Acquire(object obj)
         {
             return TryAcquire(obj, oneShot: false);
         }
 
-        // 1 - success
+        // -1 - success
         // 0 - failed
         // syncIndex - retry with the Lock
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
@@ -286,14 +286,14 @@ public static unsafe int TryAcquire(object obj, bool oneShot = true)
                     {
                         if (Interlocked.CompareExchange(ref *pHeader, oldBits | currentThreadID, oldBits) == oldBits)
                         {
-                            return 1;
+                            return -1;
                         }
                     }
                     else if (GetSyncEntryIndex(oldBits, out int syncIndex))
                     {
                         if (SyncTable.GetLockObject(syncIndex).TryAcquireOneShot(currentThreadID))
                         {
-                            return 1;
+                            return -1;
                         }
 
                         // has sync entry -> slow path
@@ -306,7 +306,7 @@ public static unsafe int TryAcquire(object obj, bool oneShot = true)
         }
 
         // handling uncommon cases here - recursive lock, contention, retries
-        // 1 - success
+        // -1 - success
         // 0 - failed
         // syncIndex - retry with the Lock
         private static unsafe int TryAcquireUncommon(object obj, bool oneShot)
@@ -341,7 +341,7 @@ private static unsafe int TryAcquireUncommon(object obj, bool oneShot)
                             int newBits = oldBits | currentThreadID;
                             if (Interlocked.CompareExchange(ref *pHeader, newBits, oldBits) == oldBits)
                             {
-                                return 1;
+                                return -1;
                             }
 
                             // contention on a lock that noone owned,
@@ -370,7 +370,7 @@ private static unsafe int TryAcquireUncommon(object obj, bool oneShot)
                             {
                                 if (Interlocked.CompareExchange(ref *pHeader, newBits, oldBits) == oldBits)
                                 {
-                                    return 1;
+                                    return -1;
                                 }
 
                                 // rare contention on owned lock,

diff --git a/src/coreclr/nativeaot/System.Private.CoreLib/src/System/Threading/SyncTable.cs b/src/coreclr/nativeaot/System.Private.CoreLib/src/System/Threading/SyncTable.cs
@@ -52,7 +52,7 @@ internal static class SyncTable
         /// </summary>
 #if DEBUG
         // Exercise table expansion more frequently in debug builds
-        private const int InitialSize = 2;
+        private const int InitialSize = 1;
 #else
         private const int InitialSize = 1 << 7;
 #endif
@@ -78,11 +78,11 @@ internal static class SyncTable
         private static int s_freeEntryList;
 
         /// <summary>
-        /// The index of the lowest never used entry.  We skip the 0th and 1st entries and start with 2.
+        /// The index of the lowest never used entry.  We skip the 0th entry and start with 1.
         /// If all entries have been used, s_unusedEntryIndex == s_entries.Length.  This counter
         /// never decreases.
         /// </summary>
-        private static int s_unusedEntryIndex = 2;
+        private static int s_unusedEntryIndex = 1;
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         private static ref Entry UnsafeEntryRef(int i)