Fix an issue where GCStress allocated objects using the Gen 0 alloc context (#10322)

* Fix an issue where GCStress allocated objects using the Gen 0 alloc context

* Remove a GCStress MaybeTrigger on LOH allocations that attempted to use the gen 0 alloc context

3 files changed, 15 insertions, 3 deletions

diff --git a/src/vm/gccover.cpp b/src/vm/gccover.cpp
index 02bb0de5e0..3e195796b4 100644
--- a/src/vm/gccover.cpp
+++ b/src/vm/gccover.cpp
@@ -1759,7 +1759,10 @@ void DoGcStress (PCONTEXT regs, MethodDesc *pMD)
     // Do the actual stress work
     //
 
-    if (!GCHeapUtilities::GetGCHeap()->StressHeap())
+    // BUG(github #10318) - when not using allocation contexts, the alloc lock
+    // must be acquired here. Until fixed, this assert prevents random heap corruption.
+    assert(GCHeapUtilities::UseThreadAllocationContexts());
+    if (!GCHeapUtilities::GetGCHeap()->StressHeap(GetThread()->GetAllocContext()))
         UpdateGCStressInstructionWithoutGC ();
 
     // Must flush instruction cache before returning as instruction has been modified.
diff --git a/src/vm/gcstress.h b/src/vm/gcstress.h
index 04487c611e..edf92a947c 100644
--- a/src/vm/gcstress.h
+++ b/src/vm/gcstress.h
@@ -286,7 +286,12 @@ namespace _GCStress
     public:
         FORCEINLINE
         static void Trigger()
-        { GCHeapUtilities::GetGCHeap()->StressHeap(); }
+        {
+            // BUG(github #10318) - when not using allocation contexts, the alloc lock
+            // must be acquired here. Until fixed, this assert prevents random heap corruption.
+            _ASSERTE(GCHeapUtilities::UseThreadAllocationContexts());
+            GCHeapUtilities::GetGCHeap()->StressHeap(GetThread()->GetAllocContext());
+        }
 
         FORCEINLINE
         static void Trigger(::gc_alloc_context* acontext)
diff --git a/src/vm/threadsuspend.cpp b/src/vm/threadsuspend.cpp
index 52c4aa62c3..10032fd08f 100644
--- a/src/vm/threadsuspend.cpp
+++ b/src/vm/threadsuspend.cpp
@@ -3495,7 +3495,11 @@ void Thread::PerformPreemptiveGC()
     {
         GCX_COOP();
         m_bGCStressing = TRUE;
-        GCHeapUtilities::GetGCHeap()->StressHeap();
+
+        // BUG(github #10318) - when not using allocation contexts, the alloc lock
+        // must be acquired here. Until fixed, this assert prevents random heap corruption.
+        _ASSERTE(GCHeapUtilities::UseThreadAllocationContexts());
+        GCHeapUtilities::GetGCHeap()->StressHeap(GetThread()->GetAllocContext());
         m_bGCStressing = FALSE;
     }
     m_GCOnTransitionsOK = TRUE;