[release/8.0-staging] Move a lock to protect m_pDynamicStaticsInfo (#…

…97352)

* Move a lock to protect m_pDynamicStaticsInfo

* apply feedback

* cast to LONG

* Fix access to m_pDynamicStaticsInfo (#97353)

- Remove race condition where it is possible that an updated dynamic statics info pointer is published without ensuring that the data is also considered written.
- Use VolatileLoadWithoutBarrier at the read site (where locks are not taken) to ensure that there are no difficult to examine reads of this pointer.

---------

Co-authored-by: Hyungju Lee <[email protected]>
Co-authored-by: David Wrighton <[email protected]>

src/coreclr/vm/ceeload.cpp

@@ -1550,29 +1550,25 @@ DWORD Module::AllocateDynamicEntry(MethodTable *pMT)
     }
     CONTRACTL_END;
 
-    DWORD newId = InterlockedExchangeAdd((LONG*)&m_cDynamicEntries, 1);
+    CrstHolder ch(&m_Crst);
+    DWORD newId = (LONG)m_cDynamicEntries++;
 
-    if (newId >= VolatileLoad(&m_maxDynamicEntries))
+    if (newId >= m_maxDynamicEntries)
     {
-        CrstHolder ch(&m_Crst);
-
-        if (newId >= m_maxDynamicEntries)
+        SIZE_T maxDynamicEntries = max(16, m_maxDynamicEntries);
+        while (maxDynamicEntries <= newId)
         {
-            SIZE_T maxDynamicEntries = max(16, m_maxDynamicEntries);
-            while (maxDynamicEntries <= newId)
-            {
-                maxDynamicEntries *= 2;
-            }
+            maxDynamicEntries *= 2;
+        }
 
-            DynamicStaticsInfo* pNewDynamicStaticsInfo = (DynamicStaticsInfo*)
-                (void*)GetLoaderAllocator()->GetHighFrequencyHeap()->AllocMem(S_SIZE_T(sizeof(DynamicStaticsInfo)) * S_SIZE_T(maxDynamicEntries));
+        DynamicStaticsInfo* pNewDynamicStaticsInfo = (DynamicStaticsInfo*)
+            (void*)GetLoaderAllocator()->GetHighFrequencyHeap()->AllocMem(S_SIZE_T(sizeof(DynamicStaticsInfo)) * S_SIZE_T(maxDynamicEntries));
 
-            if (m_pDynamicStaticsInfo)
-                memcpy(pNewDynamicStaticsInfo, m_pDynamicStaticsInfo, sizeof(DynamicStaticsInfo) * m_maxDynamicEntries);
+        if (m_pDynamicStaticsInfo)
+            memcpy(pNewDynamicStaticsInfo, m_pDynamicStaticsInfo, sizeof(DynamicStaticsInfo) * m_maxDynamicEntries);
 
-            m_pDynamicStaticsInfo = pNewDynamicStaticsInfo;
-            VolatileStore(&m_maxDynamicEntries, maxDynamicEntries);
-        }
+        VolatileStore(&m_pDynamicStaticsInfo, pNewDynamicStaticsInfo);
+        m_maxDynamicEntries = maxDynamicEntries;
     }
 
     m_pDynamicStaticsInfo[newId].pEnclosingMT = pMT;

src/coreclr/vm/ceeload.inl

@@ -463,7 +463,7 @@ inline MethodTable* Module::GetDynamicClassMT(DWORD dynamicClassID)
 {
     LIMITED_METHOD_CONTRACT;
     _ASSERTE(m_cDynamicEntries > dynamicClassID);
-    return m_pDynamicStaticsInfo[dynamicClassID].pEnclosingMT;
+    return VolatileLoadWithoutBarrier(&m_pDynamicStaticsInfo)[dynamicClassID].pEnclosingMT;
 }
 
 #ifdef FEATURE_CODE_VERSIONING