Do not pin free object for STRESS_REGIONS (#49547)

1 files changed, 9 insertions, 8 deletions

diff --git a/src/coreclr/gc/gc.cpp b/src/coreclr/gc/gc.cpp
index f5fb30c3f5d..9307b16a9a5 100644
--- a/src/coreclr/gc/gc.cpp
+++ b/src/coreclr/gc/gc.cpp
@@ -22994,18 +22994,19 @@ void gc_heap::mark_phase (int condemned_gen_number, BOOL mark_only_p)
             if ((num_gen0_regions % pinning_seg_interval) == 0)
             {
                 int align_const = get_alignment_constant (TRUE);
-                // Pinning the first object in the region.
-                uint8_t* obj_to_pin = heap_segment_mem (gen0_region);
-                pin_by_gc (obj_to_pin);
-
-                obj_to_pin += Align (size (obj_to_pin), align_const);
-                // Pinning the middle object in the region.
+                // Pinning the first and the middle object in the region.
+                uint8_t* boundary = heap_segment_mem (gen0_region);
+                uint8_t* obj_to_pin = boundary;
+                int num_pinned_objs = 0;
                 while (obj_to_pin < heap_segment_allocated (gen0_region))
                 {
-                    if (obj_to_pin > region_mid)
+                    if (obj_to_pin >= boundary && !((CObjectHeader*)obj_to_pin)->IsFree())
                     {
                         pin_by_gc (obj_to_pin);
-                        break;
+                        num_pinned_objs++;
+                        if (num_pinned_objs >= 2)
+                            break;
+                        boundary += (gen0_region_size / 2) + 1;
                     }
                     obj_to_pin += Align (size (obj_to_pin), align_const);
                 }